Vitamin D, Iron, B12: The Deficiencies Half of Britain Doesn’t Know It Has

Almost one in five Britons has low vitamin D. Nearly one in three women of reproductive age is iron-deficient. And vitamin B12 deficiency quietly affects around one in five adults over 60. Three conditions. One simple blood test. Millions of people who have no idea.

Tiredness has become so normalised in modern Britain that most people no longer think of it as a symptom. They think of it as a lifestyle. Work too hard, sleep too little, eat on the run — of course you are exhausted. That framing, while understandable, is also dangerous, because it provides a convincing cover story for three of the most prevalent, most underdiagnosed, and most easily treated nutrient deficiencies in the country: low vitamin D, iron deficiency, and vitamin B12 deficiency.

These three conditions are not exotic. They are not rare. They are not the kind of thing that only affects people with unusual diets or serious illness. They are staggeringly common, they present with symptoms that overlap confusingly with ordinary fatigue and stress, and a significant proportion of those affected have never been told their levels are low — because they have never been tested.

This article sets out the evidence: who is affected, why they are affected, what the risks of leaving these deficiencies untreated actually are, and what a straightforward blood test can reveal. The goal is not to alarm, but to inform — because knowing your numbers is the only way to act on them.

The Scale of the Problem: Three Deficiencies, Millions of People

Start with the numbers, because they are striking. According to the Scientific Advisory Committee on Nutrition (SACN) and data from NHS clinical practice, almost a fifth of the UK adult population has low vitamin D status. Analysis of the UK Biobank — a prospective study of nearly half a million middle-aged adults — found that in winter and spring, around 20 to 23 per cent of participants met the clinical definition of vitamin D deficiency (serum 25-hydroxyvitamin D below 25 nmol/L), with rates rising sharply among people of Asian and Black heritage and among those living in northern parts of the country. In summer and autumn the picture improves, but only modestly for most groups, and not at all for those with darker skin pigmentation, who require significantly more sun exposure to synthesise the same quantity of vitamin D.

Iron tells a similarly sobering story. A landmark 2025 study published in the British Journal of General Practice by researchers from the University of Oxford — drawing on electronic health records from more than 600,000 people in England — confirmed that iron deficiency anaemia affects roughly 3 per cent of adult men and 8 per cent of adult women in the UK, consistent with NICE estimates. But anaemia is only the end stage of iron deficiency. A separate 2025 analysis published in Frontiers in Nutrition, examining more than 33,000 apparently healthy adults who attended private health checks across the UK, found that 17 per cent had absolute iron deficiency — rising to 31.6 per cent among women, and to over 35 per cent among women aged 18 to 49. More than half of those affected reported no symptoms at all.

For vitamin B12, the picture is perhaps the most under-appreciated of the three. NHS clinical guidance from South West London Integrated Care Board, drawing on NICE data, puts the prevalence of B12 deficiency at around 6 per cent in adults under 60, rising to approximately 20 per cent in those aged over 60. Among vegans, the figure is considerably higher: the EPIC-Oxford cohort study, conducted across British general practices, found that 52 per cent of male vegans and 7 per cent of male vegetarians met the criteria for vitamin B12 deficiency. NICE published new clinical guidelines on B12 deficiency diagnosis and management in 2024 (NG239), a recognition that both awareness and clinical practice needed updating.

Vitamin D: Britain’s Sunshine Deficit

Vitamin D occupies an unusual place in human physiology. Unlike most nutrients, the body can manufacture it itself — but only when the skin is exposed to ultraviolet B (UVB) radiation from sunlight. That dependency makes geographical location a primary determinant of vitamin D status, and for a country like the United Kingdom, it creates a structural vulnerability that no amount of good dietary intention can fully compensate for.

Between October and early March, the angle of the sun at UK latitudes means that UVB radiation is simply not strong enough to stimulate meaningful vitamin D synthesis in the skin, regardless of how much time a person spends outdoors. This is not a marginal issue. It is a fact of physics that affects every single person living on these islands during the winter months, without exception. The NHS has acknowledged this explicitly: during the autumn and winter, the government advises that everyone — including pregnant and breastfeeding women — should consider taking a daily supplement containing 10 micrograms (400 IU) of vitamin D.

What vitamin D actually does

Despite being called a vitamin, vitamin D functions in the body more like a hormone. The liver converts it into 25-hydroxyvitamin D (the form measured in blood tests), which the kidneys then convert into its active form, calcitriol. In that active form, it regulates the absorption of calcium and phosphate from the gut — which is why vitamin D deficiency is most visibly associated with bone disease: rickets in children, osteomalacia in adults, and a significantly elevated risk of osteoporosis and fracture in older people.

But the role of vitamin D extends well beyond bone. Vitamin D receptors are present in nearly every tissue in the body, including the brain, heart, immune cells, and skeletal muscle. Research has consistently linked adequate vitamin D status with better immune function, reduced susceptibility to respiratory infections, improved muscle strength in older adults, and lower rates of certain autoimmune conditions. The evidence is strongest and most consistent for musculoskeletal outcomes, which is the primary basis for SACN recommendations, but the broader picture is one of a nutrient that is foundational to general health in ways that are still being fully mapped.

Who is most at risk in the UK?

Everyone in the UK is at some risk during the winter months, but certain groups face a substantially elevated risk year-round. People with darker skin pigmentation produce less vitamin D from the same amount of sun exposure, because melanin — the pigment responsible for skin colour — acts as a partial UV filter. The UK Biobank analysis found that in winter and spring, 57.2 per cent of adults of Asian ancestry and 38.5 per cent of adults of Black African ancestry met the clinical definition of vitamin D deficiency, compared with 17.5 per cent of white European participants.

Older adults are also particularly vulnerable. Ageing reduces the skin’s capacity to synthesise vitamin D, and many older people spend less time outdoors. People who cover most of their skin for cultural or religious reasons, those with obesity (in whom vitamin D can become sequestered in fat tissue), and those with conditions affecting fat absorption — including Crohn’s disease, coeliac disease, and liver or kidney disease — are also at significantly elevated risk.

What makes the UK’s situation unusual within Europe is the absence of mandatory vitamin D food fortification. Many countries — including the United States, Canada, and Sweden — add vitamin D to staple foods such as milk or margarine as a public health measure. The UK does not have a comprehensive fortification programme, which means population intakes remain low. According to data from the National Diet and Nutrition Survey (NDNS), dietary intake of vitamin D is inadequate across virtually all age and sex groups in Britain — the proportion of people meeting the SACN reference nutrient intake of 10 micrograms per day through diet alone ranges from near zero to at most a few per cent.

Symptoms and consequences of deficiency

Mild vitamin D deficiency often produces no obvious symptoms — or symptoms so vague that they are easily dismissed. These can include fatigue, muscle weakness, bone or joint pain, low mood, and a general sense of being run down. More severe or prolonged deficiency carries clearer consequences: bone pain and tenderness, increased susceptibility to fractures, muscle weakness that impairs balance and raises the risk of falls in older adults, and, in children, the bone deformities characteristic of rickets — a condition that had been thought largely eradicated in Britain but has seen a worrying resurgence in recent years, particularly among children of South Asian heritage.

Iron: The Invisible Drain on Your Energy

Iron is the most abundant trace mineral in the human body, and for good reason. It is essential for the production of haemoglobin — the protein in red blood cells that carries oxygen from the lungs to every tissue in the body. Without sufficient iron, haemoglobin production falls, red blood cells become smaller and paler, and the body’s cells receive less oxygen than they need to function optimally. The result is iron deficiency anaemia, the single most common nutritional deficiency in the world, affecting an estimated 1.2 billion people globally according to the World Health Organisation.

But anaemia — clinically defined as haemoglobin levels below a specified threshold — is not the starting point of iron deficiency. It is the end point. Iron depletion follows a progressive pattern. First, the body draws down its stored iron reserves (ferritin). Then, iron transport becomes impaired. Only at the final stage, when iron stores are exhausted and haemoglobin synthesis cannot be maintained, does the blood count fall into the anaemic range. This means that millions of people are functionally iron-deficient — experiencing real, measurable effects on their energy, cognition, and physical performance — while their haemoglobin level still falls within the normal range on a standard blood count. Their full blood count comes back unremarkable, and they are told everything looks fine.

The ferritin gap

This is why ferritin — the protein that stores iron in the body — is such an important and underutilised test. A serum ferritin test gives a direct measure of iron stores, and a low ferritin level indicates depletion even before anaemia develops. Clinicians at the Royal College of Pathologists have described iron deficiency without anaemia as a “diagnosis that matters,” arguing that the condition causes genuine, debilitating symptoms that warrant treatment — not reassurance that the blood count is normal.

The symptoms of iron deficiency — whether or not it has progressed to anaemia — include persistent fatigue and weakness, breathlessness on exertion, palpitations, difficulty concentrating, headaches, cold hands and feet, pale skin, brittle nails, and hair loss. One of the more distinctive manifestations is pica: an unusual craving for non-food items such as ice, clay, or paper. Another is restless legs syndrome — an irresistible urge to move the legs, particularly at night — which has a well-documented association with iron deficiency.

Why women bear the heaviest burden

Iron deficiency is not an equal-opportunity condition. Women — particularly those of reproductive age — carry a disproportionate share of the burden, for a reason that is as simple as it is frequently overlooked: monthly blood loss through menstruation. Around one in three women suffers from heavy menstrual bleeding, defined as blood loss exceeding 80 millilitres per cycle, and this is by far the most common cause of iron deficiency in women aged 15 to 50 in the UK.

The 2025 study published in Frontiers in Nutrition — which examined 33,029 adults attending private health checks across the UK — found that nearly one in three women (31.6 per cent) showed signs of absolute iron deficiency, with rates exceeding 35 per cent in the 18-to-49 age bracket. A separate study published in 2025, comparing UK and Australian women of reproductive age, found that 19.2 per cent of UK women were anaemic — roughly double the rate found among their Australian counterparts — and that among anaemic UK women, 59.4 per cent also had heavy menstrual bleeding. These are not marginal statistics. They represent a substantial public health burden that, because it is so often dismissed as simply being “tired all the time,” goes underinvestigated and undertreated.

Pregnancy compounds the problem further. During pregnancy, iron requirements rise sharply to support the expanding blood volume, placental development, and the iron needs of the growing foetus. Maternal iron deficiency has been associated with low birth weight, preterm delivery, and impaired foetal brain development. UK guidelines on the management of iron deficiency in pregnancy have been in place since 2012 and were updated in 2020, recommending that haemoglobin be checked at booking and at 28 weeks — but surveys continue to show inconsistent adherence to these protocols across NHS trusts.

Iron and men: not immune, but different

Men are far less commonly affected by dietary or menstruation-related iron deficiency, but they are not immune. In men and postmenopausal women, iron deficiency anaemia — when it does occur — is more likely to have an underlying pathological cause, including gastrointestinal blood loss from an ulcer, inflammatory bowel disease, or, importantly, colorectal cancer. According to British Society of Gastroenterology guidelines and NHS clinical guidance, iron deficiency anaemia in men of any age and in postmenopausal women warrants investigation to exclude gastrointestinal malignancy. In this population, the blood test is not just revealing a deficiency — it can be the first clue to something that requires urgent attention.

Vitamin B12: The Nervous System Under Threat

If vitamin D deficiency is Britain’s most widespread nutritional blind spot, and iron deficiency its most physically debilitating, then vitamin B12 deficiency may be its most insidious. Left untreated for long enough, it can cause damage to the nervous system that is irreversible. And yet it frequently goes undetected for years — not because the blood test is technically difficult, but because the symptoms are so varied and non-specific that clinicians often do not think to test for it, and patients rarely suspect it.

Vitamin B12 — also known as cobalamin — is essential for DNA synthesis, the production of red blood cells, and, critically, the maintenance of the myelin sheaths that insulate nerve fibres throughout the body. Myelin is to a nerve fibre what insulation is to an electrical cable: without it, signals degrade, misfire, or fail to travel at all. When B12 deficiency damages myelin, the consequences range from tingling and numbness in the extremities to difficulty walking, problems with memory and cognition, and, in severe or longstanding cases, irreversible dementia and paralysis.

The slow burn of depletion

One of the reasons B12 deficiency is so easily missed is the timeline. The liver stores large quantities of vitamin B12 — enough, in most cases, to sustain normal function for two to four years even in the complete absence of dietary intake. This means the gap between the onset of deficiency (whether from inadequate intake, impaired absorption, or both) and the appearance of clinical symptoms can be enormous. A person may have been B12-deficient for years before they develop recognisable signs of neurological damage — by which point the window for full recovery may have narrowed significantly.

This slow depletion dynamic also means that standard blood tests can be misleading. Serum B12 levels can appear normal even when functional deficiency — the state in which the body cannot actually use the B12 it has — is present. More specific markers, including holotranscobalamin (the “active” fraction of B12 that cells can actually take up) and methylmalonic acid (which accumulates when B12-dependent enzymatic pathways are impaired), provide a more reliable picture. NICE’s 2024 guideline on vitamin B12 deficiency in over-16s acknowledges this diagnostic complexity and recommends a more nuanced approach to interpretation than simply comparing serum B12 to a reference range.

Causes: absorption matters as much as intake

Vitamin B12 is found almost exclusively in animal-derived foods — meat, fish, eggs, and dairy products. This makes dietary deficiency straightforward in people following vegan diets, and the evidence is clear: the EPIC-Oxford cohort study, one of the largest long-term dietary studies conducted in the UK, found that 52 per cent of male vegans and 7 per cent of male vegetarians were vitamin B12 deficient based on serum measurements. Unsupplemented vegans showed significantly lower B12 levels, higher homocysteine (a marker of metabolic stress associated with B12 deficiency), and elevated methylmalonic acid compared with omnivores, according to a 2024 meta-analysis from the University of Surrey.

But dietary intake is only one side of the story. In older adults — who represent the largest single group affected by B12 deficiency in the UK — the problem is more often one of impaired absorption. The absorption of B12 from food requires a protein produced by the stomach called intrinsic factor. Two conditions disrupt this process. Pernicious anaemia — an autoimmune condition in which the body attacks the stomach cells that produce intrinsic factor — is the most common cause of severe B12 deficiency in the UK and is more prevalent in those over 70. Food-cobalamin malabsorption, a related but distinct condition linked to gastric atrophy, reduced stomach acid production, and long-term use of proton pump inhibitors or metformin (a widely prescribed diabetes medication), is estimated to account for 30 to 50 per cent of subclinical B12 deficiency in older people.

This matters because food-cobalamin malabsorption can be treated with oral B12 supplements — the free, crystalline form of B12 in supplements is absorbed without needing intrinsic factor — whereas pernicious anaemia requires intramuscular injections. The distinction is critical, and it cannot be made without proper investigation.

Symptoms to take seriously

The symptom picture for B12 deficiency is wide and easily confused with other conditions. Fatigue, weakness, and shortness of breath are common and often attributed to anaemia — which B12 deficiency can indeed cause, producing a distinctive pattern of enlarged, immature red blood cells (macrocytic anaemia). But the neurological and psychiatric symptoms are frequently underappreciated: tingling or numbness in the hands and feet, balance problems, difficulty walking, memory difficulties, depression, irritability, and cognitive decline. In severe or untreated cases, subacute combined degeneration of the spinal cord — a progressive, potentially irreversible condition — can develop. The neurological damage from prolonged B12 deficiency can, in some cases, precede any abnormality in the blood count, which is why a normal full blood count does not rule out clinically significant deficiency.

The Overlap Problem: When Three Deficiencies Masquerade as One

One of the clinical challenges that makes these three deficiencies particularly difficult to identify and manage is the degree to which their symptom profiles overlap — with each other and with the symptoms of common mental health conditions, thyroid disorders, and general burnout.

Fatigue, low mood, poor concentration, and reduced physical stamina are features of vitamin D deficiency, iron deficiency, and B12 deficiency simultaneously. A person who is simultaneously low in all three — which is not unusual, particularly in vegans or people following restrictive diets — may experience a cumulative burden of symptoms that is far greater than any single deficiency would produce, and far harder to disentangle without specific testing.

The overlap extends beyond symptoms. Both iron deficiency and B12 deficiency affect red blood cell production, but in different directions: iron deficiency produces small, pale red blood cells (microcytic anaemia), while B12 deficiency produces large, immature ones (macrocytic anaemia). When both deficiencies coexist — which is possible, particularly in people with coeliac disease or inflammatory bowel disease — the two effects can partially cancel each other out, producing a blood count that appears deceptively normal. This is a well-documented diagnostic pitfall that requires looking at iron markers and B12 levels individually, rather than relying solely on the overall blood count.

Who Is Most at Risk: A Practical Guide

While no one is entirely exempt from these deficiencies, certain groups face a substantially higher risk and deserve particular attention.

It is worth noting that deprivation is itself a risk factor across all three deficiencies. People from lower-income backgrounds are more likely to rely on cheaper, more heavily processed foods with lower micronutrient density; are less likely to use supplements; and may face greater barriers to accessing primary care. The 2025 Frontiers in Nutrition study noted pointedly that its cohort of health-conscious private health-check attendees likely underestimates the true prevalence of deficiency in the general population — meaning the real numbers may be worse than the headline figures suggest.

Getting Tested: What the Blood Work Actually Shows

Understanding what to ask for when you book a blood test is half the battle. A standard NHS full blood count (FBC), which GPs often use as a baseline, is useful but limited. It will detect anaemia — whether from iron, B12, or another cause — once it has developed. It will not directly measure iron stores, vitamin D levels, or B12 status in detail. If you are concerned about any of these deficiencies, it is worth understanding the specific tests involved.

For vitamin D, the relevant test is a serum 25-hydroxyvitamin D level (written as 25(OH)D). The NHS defines deficiency as a level below 25 nmol/L and insufficiency as below 50 nmol/L, though some researchers argue that optimal health is associated with levels closer to 75 nmol/L or above. NICE does not currently recommend routine screening of vitamin D levels in the general population, instead advising a targeted approach for those with risk factors. In practice, this means asking your GP if you have any of the recognised risk factors for deficiency — and being aware that home testing kits, which use a finger-prick blood sample analysed by an accredited NHS laboratory, are now widely available and can be a practical alternative for those who face barriers to in-clinic testing.

For iron, the most informative combination of tests is a full blood count plus a serum ferritin level. The FBC identifies anaemia; the ferritin test measures iron stores independently of the blood count. Both are typically available through NHS primary care. If ferritin comes back low, additional iron studies — including serum iron, transferrin saturation, and transferrin levels — can help characterise the degree of depletion and guide treatment decisions. For women with suspected heavy menstrual bleeding as a contributing cause, that conversation warrants separate attention.

For vitamin B12, the standard test is a serum cobalamin level. A result below 200 ng/L (or 148 pmol/L, depending on the laboratory’s units) is generally considered consistent with deficiency in most NHS contexts. However, as the 2024 NICE guideline (NG239) acknowledges, the relationship between serum B12 and actual cellular B12 function is imperfect. If B12 comes back borderline, or if symptoms suggest neurological involvement, more specific markers — holotranscobalamin (active B12) and methylmalonic acid — can provide a clearer picture of whether deficiency is functionally significant. Intrinsic factor antibodies can be tested to investigate for pernicious anaemia.

All three tests can be requested through your GP, though NHS availability varies by region and clinical priority. Private blood testing services, including at-home panels, can offer a faster or more convenient alternative — and a growing number of platforms allow you to order a comprehensive micronutrient panel that covers vitamin D, iron markers (including ferritin), and active B12 simultaneously.

What to Do If Your Results Come Back Low

A below-range result on any of these tests is not a crisis — it is information. And information, in this context, is the starting point for intervention. The good news is that all three deficiencies are manageable, and in many cases, highly treatable.

Vitamin D

The first step, for anyone not already doing so, is supplementation. SACN recommends 10 micrograms (400 IU) of vitamin D daily as a general preventive measure for the whole UK population during the autumn and winter. For those already deficient, higher doses — often 800 to 1,000 IU daily, and in some cases a short course of loading doses under medical supervision — may be recommended. Vitamin D3 (cholecalciferol) is generally considered more effective than D2 at raising serum levels. The NHS advises that supplements should not exceed 100 micrograms (4,000 IU) per day without medical supervision, as very high doses over sustained periods can cause toxicity.

Dietary sources of vitamin D include oily fish (salmon, mackerel, sardines), eggs (particularly the yolk), and fortified foods such as some breakfast cereals and plant-based milks. However, as noted above, diet alone is rarely sufficient to maintain adequate vitamin D status in the UK — supplements remain essential for most people, most of the year.

Iron

Oral iron supplements — typically ferrous sulphate, ferrous gluconate, or ferrous fumarate — are the first-line treatment for iron deficiency. The NHS recommends taking these for approximately six months to replenish depleted stores, not simply to restore a normal blood count. Taking iron supplements alongside vitamin C (or a glass of orange juice) improves absorption. Gastrointestinal side effects — nausea, constipation, and dark stools — are common and can reduce adherence; taking a lower dose on alternate days has been shown to be better tolerated without meaningfully compromising efficacy.

Dietary strategies can support replenishment: haem iron from red meat, poultry, and fish is the most efficiently absorbed form. Non-haem iron from plant sources (lentils, spinach, fortified cereals, tofu) is less readily absorbed, but absorption is enhanced by eating these foods alongside vitamin C and reduced by consuming tea, coffee, or calcium-rich foods at the same meal. For people with severe deficiency, those who do not tolerate or do not respond to oral iron, or those with underlying absorption issues, intravenous iron infusion is an effective alternative increasingly available in NHS day-case settings.

It is important to identify and address the underlying cause of iron deficiency. For premenopausal women with heavy menstrual bleeding, treating the bleeding itself — through hormonal contraception, intrauterine systems, or tranexamic acid, depending on individual circumstances — may be as important as supplementing iron. For men and postmenopausal women, the GP should investigate for gastrointestinal blood loss, which may require endoscopy.

Vitamin B12

Treatment depends on the cause. For dietary deficiency — the typical scenario in vegans and some vegetarians — high-dose oral cyanocobalamin (50 to 150 micrograms daily) is effective, since supplemental B12 does not require intrinsic factor for absorption. For pernicious anaemia, in which intrinsic factor is absent and oral absorption from food is impossible, intramuscular hydroxocobalamin injections are the standard treatment in the UK: a loading course followed by injections every two to three months for life. For food-cobalamin malabsorption related to gastric atrophy or medication use, oral high-dose supplementation is typically effective.

Neurological symptoms, if present, require more frequent initial treatment and close monitoring. The earlier treatment begins, the better the prospect of full neurological recovery — which underscores why early diagnosis matters so profoundly. Neurological damage from prolonged B12 deficiency, once established, may be only partially reversible.

For anyone following a vegan diet, B12 supplementation is not optional — it is an essential part of dietary planning. The NHS, the British Dietetic Association, and every major nutrition body in the UK are unequivocal on this point. Fortified foods (certain plant-based milks, breakfast cereals, and yeast extracts) can contribute to intake, but regular testing is the only way to confirm that levels are adequate.

Making Screening a Habit: Practical Next Steps

The gap between knowing that these deficiencies are common and actually finding out whether you are affected is where most people stall. Here are practical, concrete steps to close that gap.

Start a conversation with your GP. If you have any of the risk factors described above — if you are a woman of reproductive age, over 60, vegan or vegetarian, of non-white ethnicity, pregnant, or taking long-term PPIs or metformin — raise the subject at your next appointment. Ask specifically about vitamin D, ferritin, and B12 levels, not just a standard blood count. A full blood count alone will not give you the complete picture.

Take the government’s vitamin D advice seriously — year-round if you are at risk. The NHS recommendation to supplement with 10 micrograms (400 IU) of vitamin D daily from October through March applies to everyone. For those at higher risk — darker skin, limited sun exposure, obesity, age over 65 — year-round supplementation is the more prudent approach. This is a low-cost, low-risk intervention with a strong evidence base.

If you follow a vegan or plant-based diet, supplement B12 without delay. This is not a fringe recommendation. It is the consensus position of every mainstream nutrition and medical body in the UK. Rely on fortified foods as a secondary layer of protection, not a primary source. And test your levels periodically to confirm the supplementation is working.

Consider a comprehensive micronutrient panel. Testing for vitamin D, iron (including ferritin), and B12 simultaneously is more efficient and more informative than testing each in isolation, since the symptoms overlap and the conditions can coexist. A number of accredited at-home blood testing services now offer combined panels that can be completed via finger-prick without a clinic visit — a practical option for anyone with a busy schedule, a dislike of needles, or limited access to a GP appointment. Results are reviewed by a clinician and returned with context, enabling an informed conversation with your doctor about next steps.

Track results over time. A single normal result is reassuring but not permanent. Nutritional status changes with age, diet, life stage, medication, and circumstance. For people at elevated risk, annual or biannual testing is a reasonable habit — the equivalent of checking a car’s fluid levels rather than waiting for the warning light to come on.

Conclusion: The Tests Are Simple. The Consequences of Skipping Them Are Not.

There is something counterintuitive about the idea that millions of people could be carrying significant nutritional deficiencies without knowing it. We tend to assume that if something were genuinely wrong, we would feel it — that the body would sound a clear alarm. But vitamin D, iron, and B12 deficiencies do not work that way. Their early signals are the soundtrack of everyday British life: tiredness, brain fog, low mood, general malaise. They are easy to ignore, easy to attribute to something else, and easy to live with — right up until the point when the consequences become harder to reverse.

Bone fractures. Anaemia severe enough to require transfusion. Irreversible nerve damage. Cognitive decline. These are not inevitable outcomes — but they are possible ones, in people who had no idea their levels were low because they never had a blood test to find out.

The tests themselves are not complicated. They are available through NHS primary care, through private clinics, and through an increasing range of at-home testing services. They are inexpensive. They take minutes. And the information they provide — about three of the most common and most correctable nutritional deficiencies in the country — can change the trajectory of your health in ways that are genuinely significant.

If you fall into any of the risk groups described in this article, or if you have simply never had these markers checked, the question is not whether it is worth doing. It plainly is. The question is only: when are you going to do it?