Vitamin deficiency: symptoms, causes and tests

• Biotin eingeschränkt Thinning hair is documented in genuine biotin deficiency. Without a trigger such as antiepileptics or raw egg white, though, biotin is almost never the cause.
• Folsäure eingeschränkt Possible with a pronounced folate deficiency, but the evidence is thin. Iron, your thyroid or the end of a pregnancy are more often behind it.

• Biotin eingeschränkt Soft, splitting nails go along with a genuine deficiency. The idea that biotin tablets strengthen healthy nails rests only on small studies without a placebo group.

• Vitamin B2 typisch Reddened, oily, flaking skin between the nostril and cheek, on the ears and on the eyelids fits B2 deficiency, especially if the corners of your mouth and your tongue are affected too.
• Vitamin B6 belegt EFSA, NIH and the MSD Manual name oily, flaky, reddened skin around the nose, mouth and eyebrows as a sign of B6 deficiency.
• Biotin belegt A scaly red rash around the eyes, nostrils and corners of the mouth is the classic skin sign of a genuine biotin deficiency, often colonised by Candida.

• Vitamin B3 belegt Symmetrical redness on the backs of the hands, forearms and neck that gets worse after sun exposure and turns brown, rough and flaky is the key symptom of pellagra.

• Vitamin B2 typisch Cracked corners of the mouth and chapped lips are among the signs of a longer-term B2 deficiency, usually together with a red tongue and flaky skin next to the nose.
• Vitamin B6 belegt EFSA, NIH and the MSD Manual name cracked corners of the mouth (cheilosis) as a sign of B6 deficiency. A lack of iron or B2 causes the same cracks too.
• Folsäure typisch Cracked corners of the mouth and small ulcers in the mouth are among the mucous membrane signs that can follow anaemia.
• Vitamin B12 eingeschränkt The B2 article lists B12 among the possible causes. The B12 article itself doesn't list cracked corners of the mouth as a typical sign.

• Vitamin B12 belegt Your tongue burns, reacts sensitively to sour foods and looks smooth and glossy red (Hunter's glossitis). NICE counts tongue inflammation among the common signs.
• Vitamin B2 typisch The tongue loses its papillae, becomes smooth, burns and turns magenta. This also happens with a B12, folic acid or iron deficiency.
• Folsäure typisch Your tongue burns, becomes smooth, red or swollen, and your sense of taste changes, usually after the first signs of anaemia.
• Vitamin B6 belegt EFSA, NIH and the MSD Manual list an inflamed, smooth tongue (glossitis) among the signs of B6 deficiency.
• Vitamin B3 belegt A red, swollen, painful tongue and a sore mouth are part of the full picture of pellagra.

• Vitamin B12 typisch Tingling and numbness in your feet and hands are among the first signs. Your nerves often react before your blood does, so a normal blood count doesn't rule out a deficiency.
• Vitamin B1 typisch Tingling, numbness and burning in the toes and soles of the feet, later in the hands, on both sides, is the most typical symptom (dry beriberi).
• Vitamin B6 belegt Tingling and burning in the hands and feet are described with alcohol, isoniazid and dialysis, but they can also come from too much B6 from supplements. A blood test tells the two apart.
• Vitamin E belegt Tingling, numbness, weakened reflexes and a reduced sense of vibration are part of the documented picture when fat absorption is impaired.
• Biotin belegt Tingling has been described in severe biotin deficiency (NIH). With a normal diet, this practically never happens.
• Folic acid eingeschränkt Tingling is possible, but the first suspicion is a B12 deficiency. Both levels are measured before anyone takes folic acid.
• Vitamin B5 eingeschränkt Tingling and burning only appeared in deficiency experiments in the 1950s. In everyday life, a true B5 deficiency practically never occurs.
• Vitamin B3 eingeschränkt Tingling and muscle weakness are only possible and fit other B vitamins better.

• Vitamin B12 typisch If the deficiency affects the spinal cord (subacute combined degeneration), walking becomes unsteady, especially in the dark.
• Vitamin B1 typisch Calf cramps, weak legs and an unsteady gait are part of dry beriberi.
• Vitamin E belegt According to the DGE and the MSD Manual, an unsteady gait (ataxia) is the typical sign of deficiency, especially in the dark or with your eyes closed.
• Vitamin B5 eingeschränkt All four deficient test subjects in the experiment walked unsteadily. In everyday life, a true deficiency practically never occurs.

• Vitamin B12 typisch Your skin turns pale because of the anaemia, sometimes slightly yellowish, because oversized blood cells break down faster. A normal blood count doesn't rule out a deficiency.
• Folic acid typisch Pale skin and mucous membranes are part of the anaemia with too few, oversized red blood cells (megaloblastic anaemia).
• Vitamin B6 belegt Small, pale red blood cells with a normal iron level are the classic lab finding, but rare in practice.
• Vitamin B2 typisch Only later do the corners of the mouth crack, the tongue turns magenta, and a mild anaemia shows up in the blood count.
• Vitamin A eingeschränkt Anaemia is documented, but as an iron distribution disorder in severe deficiency, not iron-deficiency anaemia.
• Vitamin C eingeschränkt Anaemia is common in scurvy, because bleeding and iron absorption suffer. As a single sign, it's only possible.
• Vitamin E eingeschränkt Haemolytic anaemia only occurs in premature babies.

• Vitamin K belegt Unexplained bruises, nosebleeds, bleeding gums and bleeding that won't stop after injuries are the only proven symptom in adults. Vitamin K deficiency only becomes likely with bowel disease, antibiotics or blood thinners.
• Vitamin C belegt Swollen, bleeding gums, pinpoint bleeds and unexplained bruises are part of scurvy.

• Vitamin D typisch Calf cramps are part of the picture of muscle weakness and bone pain in a pronounced vitamin D deficiency.
• Vitamin B1 belegt Calf cramps, weak legs and an unsteady gait are part of dry beriberi.
• Vitamin B5 eingeschränkt Muscle cramps were common among the deficient test subjects in the experiment. In everyday life, this practically never happens.

• Vitamin D typisch Weak thigh muscles, trouble climbing stairs, older people falling more often: one of the first signs.
• Vitamin E belegt Muscle weakness from myopathy in severe deficiency appears in every reference work. Everyday muscle aches aren't part of it.
• Vitamin B1 eingeschränkt Weak legs and calf cramps are part of dry beriberi, which develops over weeks.

• Vitamin D typisch Dull, deep bone pain in the pelvis, hips, thighs and lower back is among the first signs (osteomalacia). In children, rickets can follow.

• Vitamin A belegt Night blindness is the earliest and best-documented sign of vitamin A deficiency, and it improves within one to two days of taking vitamin A.
• Vitamin E belegt Night vision suffers first, the retina in the late stage. Vision problems are among the documented signs, but only after a long, severe deficiency.
• Vitamin B12 eingeschränkt Blurred vision or a blind spot can come from a damaged optic nerve. Rare, and usually after a long, severe deficiency.

• Vitamin A belegt Dry eyes, Bitot's spots and xerophthalmia are documented. They follow night blindness and point to an advanced deficiency.
• Biotin belegt Conjunctivitis without a cold is considered a sign of severe deficiency, including in inherited biotinidase deficiency.
• Vitamin D eingeschränkt Dry, burning eyes are measurably linked to low levels. That's an association, not a proven cause.
• Vitamin B2 eingeschränkt Burning, watery eyes and light sensitivity are described in severe deficiency, but explicitly rare.

• Vitamin A belegt Frequent infections are well documented, because mucous membranes harden (keratinise) and immune cells are missing. Measles runs a more severe course.
• Vitamin C belegt Poor wound healing is part of scurvy, and old scars can reopen. But vitamin C doesn't prevent colds.
• Vitamin D eingeschränkt Daily or weekly vitamin D made respiratory infections about 12% less common, most strongly in people with very low starting levels. That's a finding about supplements, not about the symptom.
• Vitamin B6 eingeschränkt Susceptibility to infections is only possible (animal and deprivation studies, non-specific).
• Vitamin E eingeschränkt The NIH names a weakened immune response in deficiency, but there's no everyday data.

• Vitamin B1 belegt A racing heart, swollen ankles and breathlessness when lying down (wet beriberi) are a late sign and can turn into heart failure within days.
• Folic acid typisch Palpitations and shortness of breath on exertion come from the anaemia.
• Vitamin B5 eingeschränkt A racing heart occurred in only a few participants in the experiment, and the cause remained unclear.

According to our 13 vitamin articles, no vitamin fits this sign. What counts as unproven is explained in each article.

According to our 13 vitamin articles, no vitamin fits this sign. What counts as unproven is explained in each article.

According to our 13 vitamin articles, no vitamin fits this sign. What counts as unproven is explained in each article.

• Vitamin B12 hoch Veganism doesn't work without a B12 supplement. Clinical signs often only appear after years, so get your levels checked regularly (DGE 2024).
• Vitamin B2 erhöht The DGE rates riboflavin as potentially critical on a vegan diet. In a Berlin study, 36% were below the lab range, compared with 14% of people on mixed diets.
• Vitamin A erhöht Lower blood levels than on a mixed diet, but no deficiency. Beta-carotene is only converted at a ratio of 12:1.

• Folic acid hoch Requirement: 550 µg. Only 3 to 4% of women aged 18 to 49 reach the folate level that protects the neural tube. Take 400 µg of folic acid from when you start trying for a baby until the end of week 12.
• Vitamin B12 erhöht Requirement: 4.5 to 5.5 µg. On a vegan or vegetarian diet, the infant is most at risk.
• Vitamin D erhöht Estimated value: 20 µg if your body isn't making its own. Since 2024, the Endocrine Society has recommended taking it during pregnancy.
• Vitamin B1 erhöht Severe pregnancy sickness drains the small thiamine stores within weeks.
• Vitamin B2 erhöht Requirement: 1.3 to 1.4 mg. Without dairy, it gets tight.
• Biotin erhöht Breakdown happens faster. Based on urine markers, about one in three pregnant women has a mild deficiency without symptoms. What that means is still unclear.
• Vitamin K erhöht With severe vomiting, clotting time was prolonged in 43% of cases in one study. After birth, your baby gets their own vitamin K prophylaxis.

• Vitamin B12 hoch 27% of 65- to 93-year-olds have low B12 levels (KORA-Age), because stomach acid declines. Symptoms are often mistaken for normal ageing.
• Vitamin D hoch With age, the skin produces less than half the vitamin D. For people who need care, deficiency is almost the rule. From 65, the DGE recommends a supplement if you don't get enough sun.
• Vitamin B6 erhöht 16 to 24% of adults over 50 have a low PLP level. But low in the blood doesn't mean ill.
• Folic acid erhöht If you eat little, take medication or drink alcohol, you slip into deficiency more easily. It often shows up as forgetfulness.
• Vitamin B1 erhöht 40% of women over 65 don't reach the recommendation. That's intake, not a proven deficiency.
• Vitamin B2 erhöht 32% of women and 19% of men over 65 are below the recommendation, again just intake.
• Vitamin C erhöht In care homes, intake is around 50% below the reference. The risk is needing care, not age.
• Vitamin K erhöht Older age is among the groups with too little intake. The requirement rises slightly to 65 and 80 µg respectively.

• Vitamin B1 hoch The number one cause in industrialised countries. 30 to 80% of people with alcohol dependence have too little thiamine, and the S3 guideline pairs withdrawal with thiamine.
• Vitamin B6 hoch The classic: 35 of 66 people with alcohol dependence were below the lowest value seen in healthy people.
• Vitamin B3 hoch The most common cause of pellagra in Europe (35% of case reports).
• Folic acid hoch The number one cause in men. 23% of 211 people in withdrawal had a folate deficiency.
• Vitamin B2 erhöht Alongside medication, the most common reason for a genuine B2 deficiency.
• Vitamin A erhöht Liver stores drop and breakdown speeds up.
• Vitamin B12 erhöht Alcohol damages the stomach lining and the liver, where B12 is stored.
• Vitamin C erhöht People who drink a lot eat little fresh food. The liver is under oxidative stress.
• Biotin erhöht 15% of people with alcohol dependence have a low level.
• Vitamin B5 erhöht Only a weak indication from a small study in 1976.

• Vitamin B12 hoch The silent B12 thief: the risk rises with dose and duration. After five years, 19% had low or borderline levels, compared with 10% on placebo.
• Folic acid erhöht Metformin is on the list of medicines that lower folate levels, and it also interferes with B12 absorption.

• Vitamin B12 hoch After two years of use, the risk rises by 65% with PPIs and by 25% with H2 blockers. The link is an association, so get a baseline value measured before long-term therapy.

• Vitamin B1 erhöht Furosemide and other loop diuretics flush thiamine out through the kidneys, as shown in patients with heart failure.

• Vitamin B12 hoch Stomach reduction, bypass, or removal of the stomach or ileum all reduce absorption. NICE then recommends replacement without testing first.
• Vitamin B1 hoch 7% before surgery, 19% three months afterwards. Here, a deficiency becomes dangerous faster than in other cases.
• Vitamin A hoch 35% deficient six weeks after bypass, 18% after a year.
• Folic acid erhöht Small bowel surgery and stomach reduction lower the level. The guideline recommends 600 µg per day.
• Vitamin C erhöht Absorption problems after gastric bypass and with short bowel syndrome.
• Vitamin E erhöht Risk rises after gastric bypass; clinical signs are rarely documented.
• Vitamin K erhöht Short bowel syndrome and gastric bypass raise the risk.

• Vitamin A hoch Fat malabsorption is the most common cause of vitamin A deficiency in Germany (Crohn's disease, coeliac disease, cystic fibrosis).
• Vitamin E hoch Fat malabsorption is the most common cause here. In cystic fibrosis, 10 to 35% lack fat-soluble vitamins despite taking supplements.
• Vitamin K hoch Malabsorption is the most common cause. In cystic fibrosis with a weakened pancreas, it's 78%.
• Folic acid hoch The classic lab finding in coeliac disease, with 7% still affected even on a gluten-free diet.
• Vitamin D erhöht Coeliac disease and Crohn's disease: this fat-soluble vitamin is poorly absorbed.
• Vitamin B12 erhöht Crohn's disease in the lower small intestine: the guideline recommends checking holotranscobalamin at least once a year.
• Vitamin B2 erhöht Chronic diarrhoea, coeliac disease and Crohn's disease slow down absorption.
• Vitamin B6 erhöht Low PLP levels are common, sometimes caused by inflammation alone without a true deficiency.
• Vitamin B3 erhöht Crohn's disease, coeliac disease and chronic diarrhoea are among the absorption disorders.
• Biotin erhöht In Crohn's disease and colitis, metabolic markers show a deficiency more often.
• Vitamin C erhöht Crohn's disease, ulcerative colitis and short bowel syndrome are among the causes.

• Vitamin C hoch Turnover is around 40% higher. The DGE recommends 135 mg (women) and 155 mg (men). Blood levels in people who smoke are on average 15 µmol/l lower.
• Biotin erhöht Smoking speeds up breakdown: 30% less biotin in urine.
• Vitamin B6 erhöht PLP levels drop with smoking, regardless of diet. A lab value, not a proven deficiency.

• Biotin hoch Best evidence: carbamazepine, phenytoin, phenobarbital and primidone lowered levels in 264 people.
• Folic acid erhöht Most antiepileptics lower folate or B12 in serum. Three months of supplementation normalised levels in 95%.
• Vitamin B12 erhöht Topiramate and phenobarbital are among the medicines that lower B12.
• Vitamin B6 erhöht Valproate, carbamazepine and phenytoin speed up breakdown, so PLP drops.
• Vitamin D erhöht Antiepileptics speed up vitamin D breakdown. The RKI lists them as a risk factor.