Vitamin B1 deficiency: symptoms, causes and treatment
Tingling in your feet, tiredness, a racing heart – and does heavy sweating go with it? Vitamin B1 turns sugar into energy for your nerves and heart, and your body only stores it for a few weeks. Which symptoms are proven, how much you need and where to find it.
Aktualisiert 30 September 2026 · 16 Min. Lesezeit · 51 Quellen
The key points in 30 seconds
Recommended intake from the DGE (German Nutrition Society): women 1.0 mg, men 1.1 to 1.3 mg a day, depending on age. A pork schnitzel covers that on its own; without meat, you need wholegrains, pulses and seeds.
The body only stores 30 to 50 mg of thiamine. With no intake, the store is used up in 18 days to six weeks, depending on where you start. That's why it happens so fast after stomach surgery or with persistent vomiting.
of women and 21% of men don't reach the recommended intake, according to the National Consumption Study (Nationale Verzehrsstudie). Among women over 65, it's 40%. Too little on the plate, not yet a deficiency in the blood.
Heavy sweating only appears in the textbooks for the severe cardiac form of the deficiency, never at the start. Hardly any vitamin B1 is lost through sweat; when you exercise, your need rises through the calories you burn.
Vitamin B1 deficiency symptoms: how to spot it
Vitamin B1, also known as thiamine, is the ignition key for burning sugar: without it, your nerves, brain and heart can't get energy from carbohydrates. That's why a deficiency starts quietly with tiredness despite sleep, irritability, poor memory, little appetite and weight loss, then moves on to the nerves (tingling in the feet), the heart (racing heart, swollen ankles) and, in severe deficiency, the brain (confusion, shaky eyes). It's rare in healthy people; at risk are people who drink a lot of alcohol, or who have had stomach surgery, or have diabetes, an eating disorder or weeks of vomiting. Sweating, menopause and weight gain are not among the proven symptoms.
Vitamin B1 deficiency symptoms, tingling: nerves in hands and feet
The most typical symptom: tingling, numbness and burning, first in the toes and soles of the feet, later in the hands, on both sides like socks and gloves. Doctors call this polyneuropathy; the old name is dry beriberi. Calf cramps, weak legs and an unsteady gait come with it. The longest nerve fibres need the most energy and fail first. Important: tingling in the feet has two much more common causes, diabetes and vitamin B12 deficiency. So if you have tingling, get your blood sugar, B12 and B1 checked together.
Heart, circulation and eyes
The heart muscle runs almost entirely on sugar energy, and it speaks up early: the blood vessels widen, the heart races, the skin is warm and moist, and later oedema appears at the ankles, followed by breathlessness when lying down and, in severe cases, heart failure within days (wet beriberi). Blood pressure isn't high here, but the pulse pressure is wide. The eyes aren't a vision problem but a movement problem: in severe deficiency you get involuntary eye tremors and double vision, which improve within hours with thiamine.
Vitamin B1 and sweating: does a deficiency leave you drenched?
No, as a rule it doesn't. If you sweat a lot and are otherwise healthy, you very likely don't have a vitamin B1 deficiency. Two things are backed up by evidence: sweating is a sign of wet beriberi, along with a racing heart and warm skin, so it's a late sign and never appears on its own. And sweating fits are listed in the product information for B1 injections as a rare side effect. Not backed up: any meaningful loss through sweat (one study from 1943, never confirmed), any effect on hot flushes, and the mosquito myth, which a 2022 review of 104 studies disproved. If you sweat a lot, look for the cause in the menopause, thyroid, infections, low blood sugar or medication, not in B1, B12 or folic acid.
Sweating and vitamin B1: what's true
Six claims from the internet and what the research says.
| What the studies say | Rating | |
|---|---|---|
| Sweating as an early sign | Not in any reference work; early signs are tiredness, irritability, loss of appetite | Unproven |
| Sweating in severe deficiency | Sign of wet beriberi alongside a racing heart and warm skin (MSD Manual) | Proven |
| Sweating after a B1 injection | Rare hypersensitivity according to the product information; barely described with tablets | Proven, rare |
| Loss through sweat | One study from 1943: 5 to 15%, no modern confirmation | Possible |
| B1 for hot flushes, hyperhidrosis | Not a single study found | Unproven |
| B1 against mosquitoes | 2022 review of 104 sources: doesn't work at any dose | Disproven |
Based on MSD Manual, product information for Vitamin B1-ratiopharm solution for injection, Cornbleet 1943, Shelomi 2022. Last updated 23 September 2026.
Vitamin B1 deficiency symptoms in women
The symptoms are the same, but the risks aren't. The most important reason is severe pregnancy sickness: if you can barely keep anything down for weeks, you empty the small stores, in rare cases leading to Wernicke encephalopathy (chapter 7). On top of that come the higher needs during pregnancy and breastfeeding (1.2 to 1.3 mg), eating disorders and stomach surgery for weight loss. According to the National Nutrition Survey, 32% of women don't reach the recommended intake, and from age 65 it's 40%; that means too little on the plate, not a proven deficiency. The menopause isn't part of this: there's no study showing B1 as the cause of hot flushes or mood swings, and the same goes for hair loss and weight gain.
Beriberi and Wernicke's encephalopathy: when the deficiency becomes severe
Beriberi is the old name for the severe deficiency disease: dry for the nerves, wet for the heart. The most dangerous form is Wernicke's encephalopathy: in energy-hungry areas of the brain, the tissue becomes over-acidic and swells.
From first sign to emergency
-
1
Early signsDays to weeks
Tiredness, irritability, poor appetite, bad sleep. Non-specific, but if you have a risk factor, it's the moment for a blood test.
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2
Dry beriberiWeeks
Tingling and burning in the toes and soles of the feet, calf cramps, weak legs. The nerves recover over months.
-
3
Wet beriberiDays
Racing heart, warm, moist skin, swollen ankles, breathlessness when lying down. Can turn into heart failure within days, but responds to thiamine within hours.
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4
Wernicke-KorsakoffEmergency
Confusion, shaky eye movements, double vision, unsteady gait. High-dose thiamine immediately, before any sugar is given.
Based on MSD Manual, Frontiers in Neurology 2025 and Thomson 2009. In risk groups, Wernicke's encephalopathy often develops without any earlier beriberi signs.
The classic Wernicke signs are confusion, eye movement disorders and unsteady gait, but only 10 to 16% of those affected show all three, and up to 19% show none. That's why, according to autopsy studies, it's missed during life in about 80% of cases; two of four criteria are enough to start treatment. Untreated, up to one in five people dies, and 85% of survivors are left with Korsakoff syndrome and permanent memory gaps.
Sudden confusion, shaky eyes or double vision, unsteady gait, or breathlessness with swollen legs and a racing heart, especially with heavy drinking, in withdrawal, after stomach surgery, with an eating disorder or after weeks of vomiting: call 112 or go straight to the emergency department, and tell them a vitamin B1 deficiency is possible. Thiamine is given as a drip, always before any sugar infusion.
Vitamin B1 deficiency causes: who's really at risk
A deficiency develops in four ways: too little intake (a one-sided diet, an eating disorder, alcohol instead of food), poor absorption (alcohol slows the gut transporters, stomach surgery shortens the route), higher use (pregnancy, lots of sugar, refeeding after periods of starvation) and higher loss (diabetes, water tablets, dialysis, vomiting). Usually two of these come together. First your needs, then the routes, then three questions to find out whether any apply to you.
Vitamin B1 deficiency from alcohol: why drinking robs you of B1
In industrialised countries, alcohol is the number one cause, and it works in three ways at once: less eating, because beer and wine contain practically no B1; poorer absorption, because alcohol slows the transporters in the gut wall, so in malnourished people with alcohol dependence less than a third of a tablet gets through; and less use in the damaged liver, often together with a magnesium deficiency that blocks the B1 enzymes. Niacin is also often lacking in people with alcohol dependence. The most dangerous time is withdrawal and any glucose drip without thiamine, because the sugar metabolism kicking in uses up the last remains (chapter 7).
Diabetes and water tablets: loss through the kidneys
The second route is the kidneys. In diabetes, thiamine is excreted 16 to 24 times faster, and in a British study plasma levels were 75% lower than in healthy people; a 2023 meta-analysis confirms the direction. So if you have diabetes and tingling in your feet, you have two reasons to check your B1 level. The same applies to furosemide and other loop diuretics for heart failure, whose product information explicitly mentions thiamine loss, and to dialysis. For metformin there's only a lab finding, with no proven deficiency in humans.
Stomach surgery, vomiting, eating disorders and the refeeding trap
Anything that bypasses or empties the small intestine is a risk. According to a 2023 meta-analysis, 7% of people were already deficient before gastric bypass or sleeve gastrectomy, and 19% three months afterwards. Weeks of vomiting and eating disorders empty your stores within weeks. The little-known trap is refeeding syndrome: if you start eating again after starvation, a crash diet or illness, your sugar metabolism ramps up and suddenly uses up thiamine. That's why the British NICE guideline has thiamine given upfront during the first ten days of refeeding.
Vitamin B1 thieves: what uses up or destroys B1
There's real truth behind the term. What uses up, destroys or flushes out B1:
- Alcohol: affects intake, absorption and utilisation all at once (documented).
- Sugar, white flour, polished rice: they hardly supply any B1 and use it up when burned; Type 1050 flour has five times as much as Type 405. That was the beriberi story, for which Christiaan Eijkman won the Nobel Prize in 1929 (documented).
- Water tablets, dialysis, diabetes: loss via the kidneys (documented).
- Raw freshwater fish and shellfish: the enzyme thiaminase breaks down B1, and heating stops it (documented, rare).
- Sulphite in light-coloured dried fruit and wine destroys B1 (plausible).
- Tea and coffee bind B1, but two to four cups have no effect (plausible).
- 5-fluorouracil blocks its activation (documented).
How vitamin B1 works in your body
Three stages from plate to nerve cell. Once you know them, you'll understand why your reserves last only weeks and why your brain, nerves and heart are the first to suffer.
Absorption in the small intestine
Two dedicated transporters carry thiamine from wholegrains, pulses, seeds and pork into your gut cells. They can be saturated: from a 15 mg tablet, no more than 4.5 to 5.6 mg gets through. Alcohol slows the transporters down, magnesium is needed as a helper, and after a gastric bypass part of the route is missing.
Activation and a small store
In the cell, thiamine is activated with magnesium to form thiamine diphosphate. Your whole body holds only 30 to 50 mg in reserve, mainly in the liver, heart, kidneys and brain. Without any intake, that reserve runs out in 18 days to six weeks. Any excess leaves via the kidneys once more than about 5 mg a day arrives.
How it works: sugar becomes energy
Thiamine diphosphate is the ignition key for three enzymes that turn sugar into energy. The brain, nerve fibres and heart muscle live on almost nothing else. Without thiamine, lactic acid builds up in the tissue, the longest nerve fibres in the feet fail first, the heart races, and in sensitive areas of the brain Wernicke's encephalopathy develops.
Diagnosing vitamin B1 deficiency: blood values and tests
You can measure whether you're short of B1, but the value matters less than many people think: in an emergency it isn't available, a normal value doesn't rule out a deficiency, and blood doesn't reflect what's going on in your tissue. The diagnosis is clinical: risk plus symptoms plus improvement on thiamine. Here are the tests and what they're worth.
Thiamine diphosphate in whole blood: the blood value that counts
What's measured is thiamine diphosphate (TDP) in EDTA whole blood by HPLC: the active form, 90% of which sits in the red blood cells, and more meaningful than free thiamine in serum, which only reflects your last few meals. A German lab gives 70 to 180 nmol/l as the reference range; limits vary from lab to lab, and the blood must be sent to the lab protected from light. The older transketolase test (ETKA) is increasingly being replaced. The sentence that puts it all in perspective comes from the Ärzteblatt Sachsen: “A normal thiamine level does not rule out the diagnosis.” If Wernicke is suspected, blood is taken and treatment starts immediately.
Vitamin B1 deficiency test: blood test at the doctor's or home test?
Any GP surgery can take the blood sample. If you have risk factors such as alcohol dependence, stomach surgery, dialysis or polyneuropathy, it's medically justified; without symptoms, you usually pay for it yourself. Home tests using capillary blood have no published validation study. If even a lab value from a vein can't rule out a deficiency, a drop from your fingertip certainly can't.
A value that's too high is almost never a sign of illness, but of a supplement from the days before: your body throttles absorption from about 5 mg a day, your kidneys excrete the rest, and neither EFSA nor BfR has been able to set a limit above which B1 does harm. The B vitamin with a real overdose risk is B6.
If you take a vitamin B supplement, tell the surgery, otherwise the value shows the supplement instead of your actual supply. If you have tingling in your feet, ask for vitamin B12, folic acid and your long-term blood sugar to be tested at the same time, as those are the more common causes.
Fixing a vitamin B1 deficiency: what helps and how fast
Vitamin B1 is cheap, safe and works fast when the deficiency is real. How fully you recover depends on how long your nerves and brain went without energy, and without tackling the cause the deficiency comes back. Three routes: tablets for a mild deficiency, an infusion in an emergency, and always the question of alcohol, stomach, kidneys and diet.
Tablets for a mild deficiency: thiamine or benfotiamine?
For mild polyneuropathy, the MSD Manual gives 10 to 20 mg a day for two weeks, and for advanced cases 20 to 30 mg, spread across the day because the gut transporters are saturated from about 15 mg; there's no study on morning versus evening. More important than the milligrams: magnesium, without which the B1 enzymes can't work, and the cause, otherwise the tablet is just filling a leaky barrel. Benfotiamine, the fat-soluble precursor, reaches higher blood levels but in the EU may only be used in medicines; the best study (BENDIP 2008) showed fewer symptoms in diabetic polyneuropathy, while a Cochrane review calls the evidence insufficient.
With vitamin B1, I keep seeing two mistakes. The first: someone has been taking B complex for months for tiredness even though their stores are full, and the excess just goes into the urine. The second is more dangerous: someone who drinks heavily gets tingling in their feet and waits it out. That's not about a tablet, it's about getting thiamine in quickly and at a high dose, and about talking about the cause.
Joerg Hauke, Nutrition expert, specialist reviewer of this article
Wernicke encephalopathy emergency: infusion, and thiamine before sugar
If it's suspected, there's no waiting: the European neurologists' guideline recommends 200 to 500 mg three times a day as an infusion for at least three days. The dose is that high because with a damaged gut only a fraction of oral doses arrives, and doses that were too low were linked to mortality of up to 20%. And the rule in every hospital: thiamine before glucose, because a sugar infusion without thiamine can trigger the encephalopathy in the first place. Lasting damage afterwards is the rule, not the exception.
How long does it take to correct a vitamin B1 deficiency?
It depends on the organ, and the order is well documented: your eyes improve within hours to days of the infusion, which is why the response confirms the diagnosis. Your heart follows in days, tiredness and appetite in weeks. Nerves take the longest: tingling and numbness fade over months because nerve fibres grow back slowly, and after a long history some of it stays. Your memory recovers last, and often only partly. Without a deficiency, B1 doesn't “work” in any noticeable way.
Vitamin B1 overdose and side effects: how much is too much?
You can't realistically overdose through food, and even with tablets the margin is wide: the EFSA set no upper limit in 2016, and the BfR (German Federal Institute for Risk Assessment) skipped a maximum amount in 2021 and 2024 because no harm was seen even at intakes far above the recommendations. The excess leaves the body via the kidneys. Side effects almost only come from injections: rarely hypersensitivity with sweating, a racing heart and itching, very rarely shock. With tablets, stomach pressure or headaches are only described anecdotally. Be careful with vitamin B6 in a B complex, as long-term high doses can damage nerves.
Vitamin B1 foods: where you'll find the most
B1 isn't concentrated in a handful of foods but spread across many, and two groups stand out: pork with around 1 mg per 100 g, three to ten times as much as other meats, and the outer layers of seeds and grains: wheat germ, linseed, sunflower seeds, wholegrain, pulses. The bars show the top 10 per 100 g, as eaten. Values come from the US USDA database; differences in the German Federal Food Code (BLS) are noted in the footnote.
Vitamin B1 per 100 g: top 10 plant-based and animal sources
USDA SR Legacy 2018, seeds and oats dry, pulses and rice cooked. In portions: 1 tbsp wheat germ 0.19 mg, 1 tbsp linseed 0.16, 30 g sunflower seeds 0.44, 50 g oats 0.23, 1 slice wholemeal bread 0.20, 150 g peas 0.39, 200 g brown rice 0.36 mg. Macadamia is left out on purpose (USDA 1.20, German BLS only 0.28 mg).
Vitamin B1 foods: pork, wholegrain, pulses, seeds
150 g of pork fillet gives you 1.5 mg, the same amount of chicken breast just 0.1 mg. Cooked ham and cured ham count too.
Without pork, other foods carry the day: wholegrain (oats, wholemeal bread, brown rice, wholewheat pasta with 0.16 instead of 0.02 mg), pulses (peas 0.26 mg, beans, lentils, tofu), a daily handful of seeds, and fish, where trout and salmon are far ahead of cod. Potatoes bring 0.1 mg per 100 g, vegetables mostly 0.03 to 0.1, and milk, cheese and eggs very little. Fruit sits right at the bottom: orange (0.09) and pineapple (0.08) are the best, while banana, kiwi and apple come in at 0.01 to 0.03. Light-coloured sulphured dried fruit loses almost everything to sulphite.
Wholegrain instead of white flour: where the vitamin sits in the grain
Thiamine sits on the outside of the grain, in the germ and the aleurone layer, which are lost during milling and polishing. German Federal Food Code: wheat flour Type 405 has 0.12 mg per 100 g, Type 1050 has 0.62, wholemeal flour 0.48; cooked brown rice 0.18, polished rice 0.02 to 0.03; white pasta 0.02, wholemeal pasta 0.16.
In US tables, white bread sometimes ranks above wholegrain bread because white flour is fortified with thiamine there; in Germany it's 0.17 versus 0.25 mg. B1 is water-soluble and sensitive to heat, so the way you cook matters too: cook briefly with little water and eat the cooking water, and vegetables and potatoes in their skins keep around 80%, while pasta and rice cooked in lots of water keep only 65 to 75%. Bicarbonate of soda in dough and sulphur in dried fruit destroy a large share.
Vitamin B1 in everyday life: drinkable meals
On days with canteen food, sandwiches and sweet snacks, the very food groups that supply B1 are missing, and because your stores are small, every day counts. A drinkable meal is then a reliable contribution: depending on the flavour, one bottle of Saturo contains 0.28 to 0.33 mg of vitamin B1, 25 to 30% of the reference amount, plus 25 other vitamins and minerals, 36 g of protein and 400 kcal. It doesn't replace treatment for a confirmed deficiency. EU-approved claim: thiamine contributes to normal energy metabolism, to the normal function of the nervous system, to normal psychological function and to normal heart function.
Drinkable meal: a complete meal in a bottle
26 vitamins and minerals, including vitamin B1, B6, B12 and folic acid. Thiamin contributes to normal energy metabolism and to the normal functioning of the nervous system. Reference intake for vitamin B1: 1.1 mg per day (NRV).
Pregnancy, alcohol withdrawal, stomach surgery: when you need to take a closer look at vitamin B1
In healthy people eating a mixed diet, B1 is rarely a problem. Five situations are the exception: pregnancy with vomiting, alcohol withdrawal, the time after stomach surgery, a vegan diet without the main source, pork, and sport and heat, the reason many people end up here.
Pregnancy and breastfeeding: requirements and pregnancy sickness
Your requirement rises moderately to 1.2 to 1.3 mg, which normal food covers. The risk is hyperemesis gravidarum, severe pregnancy sickness: because your stores only last a few weeks, case series describe women with eye tremors and confusion after weeks of vomiting. The consequence: if vomiting persists, thiamine is given, before any glucose infusion. For the baby, infantile beriberi has been described in breastfed infants of deficient mothers, a rarity in Germany.
Alcohol withdrawal: thiamine is part of it
In the first days without alcohol, your requirement is at its highest because the body switches over to carbohydrates. The German S3 guideline says: “During alcohol withdrawal, thiamine, possibly combined with magnesium, should be given to prevent Wernicke's encephalopathy.” It doesn't name a dose, because according to Cochrane 2013 the evidence is thin; in hospital thiamine is given as an infusion, as an outpatient as tablets far above the daily requirement. Never go through withdrawal alone or abruptly: besides the thiamine issue, seizures and delirium are a risk; the dose is decided by a doctor's practice, not the drugstore.
Anonymous and free advice: the German Centre for Addiction Issues (DHS) keeps a directory of addiction support services with counselling centres across Germany, and the BZgA provides information at kenn-dein-limit.de. Your GP is a good first point of contact and is bound by confidentiality.
After stomach surgery and with diabetes: screening, supplements, warning signs
After a gastric bypass or sleeve gastrectomy, thiamine is the nutrient whose deficiency becomes dangerous fastest: small stores, frequent vomiting in the first weeks. The American professional society recommends screening before surgery and permanent supplementation afterwards; vomiting, tingling, weak legs or confusion belong straight in the hospital that operated. With diabetes and tingling, the rule is: get your blood sugar under control, check B12 if you take metformin, and correct a B1 deficiency; according to Cochrane, B-complex products don't have enough evidence.
Vegan and vegetarian: B1 without pork
B1 isn't a critical nutrient in plant-based diets; wholegrain, pulses and seeds are the plant-based half of the top 10. But the most convenient source is missing, and if you live on toast, white pasta and ready meals as a vegan, you hit the limit faster. Your day needs several building blocks: oats, pulses, brown rice or wholemeal pasta, a handful of seeds; soy drink naturally provides 0.15 mg per 100 ml. The builder below shows how a day with and without meat reaches 1.1 mg.
Sport and heat: Your needs go up, but because of the calories, not the sweat. Every calorie you burn needs thiamine, which is why the DGE and EFSA calculate per 1,000 kcal: if you burn 3,500 kcal, you need around 1.5 mg instead of 1.0, and you get it automatically from the extra rolled oats, wholemeal pasta and pulses. No supplement needed, as long as your carbs don't come only from gels and white bread.
Common questions about vitamin B1 deficiency
Which vitamin are you missing when you sweat?
Usually none. No study links heavy sweating to a deficiency of vitamin B1, B12 or D in healthy people. B1 is only connected to sweating in the severe cardiac form of deficiency, and then it comes with a racing heart and swollen legs. Common causes are the menopause, thyroid problems, infections, low blood sugar and medication.
How do you notice a vitamin B1 deficiency?
First with tiredness, irritability, poor appetite and trouble concentrating, then with tingling and burning in the feet, calf cramps, a racing heart and swollen ankles. Confusion, jerking eye movements and unsteady walking are an emergency. Typical triggers are alcohol, stomach surgery, diabetes, eating disorders and weeks of vomiting.
What is a vitamin B1 thief?
Anything that uses up, destroys or flushes out thiamine: above all alcohol, then diuretics, dialysis and diabetes (loss through the kidneys), lots of sugar and white flour, raw freshwater fish and shellfish (thiaminase), sulphite in light-coloured dried fruit and wine, and litres of tea or coffee.
How long does it take to fix a vitamin B1 deficiency?
Anywhere from hours to months, depending on the organ: jerking eye movements and heart symptoms improve within hours to days on a drip, tiredness within weeks, and tingling in the feet over months, because nerve fibres grow back slowly. After Wernicke encephalopathy, memory problems often partly remain.
Which disease is caused by a vitamin B1 deficiency?
Beriberi and Wernicke encephalopathy. Dry beriberi is a polyneuropathy of the legs, wet beriberi is heart failure with oedema. Wernicke encephalopathy is acute brain damage with confusion, eye movement disorders and unsteady walking; if left untreated, Korsakoff syndrome follows.
Where is the most vitamin B1?
In pork (around 1 mg per 100 g) and in seeds and grains: wheat germ 1.88 mg, linseeds 1.64, sunflower seeds 1.48, rolled oats 0.46, wholemeal bread 0.39, peas 0.26. 150 g of pork fillet covers your whole day on its own; without meat, rolled oats, pulses, wholegrains and seeds together reach 1.1 mg.
Can you overdose on vitamin B1?
Not through food, and practically not through tablets either: EFSA and the BfR haven't set an upper limit, and any excess leaves your body in your urine. Side effects are rare and almost only involve injections. Be careful with B-complex products because of vitamin B6, which damages nerves at long-term doses.
Can I take vitamin B1 and magnesium together?
Yes, if you have a proven deficiency it even makes sense: the enzymes that use thiamine need magnesium, and the German S3 guideline recommends thiamine, with magnesium where appropriate, during alcohol withdrawal. Without a deficiency, the combination brings no added benefit, but does no harm either.
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Has been writing for Saturo since 2019 about nutrition, nutrients and how to get a good supply of them in everyday life.
Hat diesen Artikel am 24. September 2026 auf fachliche Richtigkeit geprüft. This content is no substitute for medical advice.
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