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Vitamin B1 (Thiamine)

Vitamin B1 (Thiamine) Quick Facts

  • Vitamin B1 is an essential nutrient, which helps to produce energy from food, contributes to metabolism of glucose and enables proper functioning of the nerves, brain, muscles and heart.
  • Healthy individuals, including pregnant and breastfeeding women and vegans, can get sufficient amounts of vitamin B1 by eating common foods, so they do not likely need supplemental vitamin B1.
  • Rarely, chronic alcoholics, people who eat unfortified polished rice as the only food, those who do not eat enough or have impaired intestinal absorption develop vitamin B1 deficiency (beriberi) with severe weakness.
  • Vitamin B1 supplements help in vitamin B1 deficiency but less likely in other health disorders.
  • Other names for vitamin B1 are thiamin, thiamine and aneurin.

Recommended Daily Intake

Recommended Dietary Allowance (RDA) for vitamin B1 for adult men is 1.2 mg/day, for women 1.1 mg/day, and 1.4 mg/day during pregnancy and breastfeeding [3].

Food Sources of Vitamin B1

Most common foods, except unfortified polished rice, contain at least moderate amounts of thiamine. Examples of foods high in thiamine:

  • PLANT FOODS: vegetarian meatless products, enriched breakfast cereals, yeast extract spread and brewer’s yeast usually contain more than 1 mg vitamin B1 per serving [14].
  • ANIMAL FOODS: pork and fish contain 0.4-0.9 mg vitamin B1 per serving.
  • Breast milk from well-nourished mothers should provide sufficient amounts of vitamin B1 for exclusively breastfed babies in their first 6 months [39,40].

Thiamine mononitrate and hydrochloride in enriched foods are safe and vegan

In the United States, flour (baked products), white rice, morning cereals and certain fruit juices are fortified with thiamine mononitrate or hydrochloride, which are synthetically produced and therefore vegan [4]; they are also generally recognized as safe (GRAS) by the Food and Drug Administration (FDA) [27].

In fortified rice, nutrients are added as a powder, so washing the rice before cooking removes most of them [7]. Storing for several months and cooking can decrease the vitamin B1 content of foods for about 50%.

Source: USDA.gov [5]

Vitamin B1 Deficiency: Who is at risk?

  • Chronic alcoholics who eat very little; alcohol also inhibits absorption of vitamin B1
  • Rarely, individuals on fad diets or fasting or starving for a prolonged time, suffering from anorexia nervosa or severe psychological or physical stress, war refugees, individuals with celiac or Crohn’s disease, chronic diarrhea, gastric bypass (bariatric surgery for weight loss), hyperthyroidism, malaria, liver disease, burns, HIV/AIDS or cancer, diabetics with kidney damage, individuals on hemodialysis and older individuals with congestive heart failure on prolonged diuretic therapy
  • In eastern countries, like Indonesia, Taiwan and Sri Lanka, deficiency, rarely, occurs in individuals eating only polished rice or cassava for a prolonged time, for example during fishing trips, and in babies breastfed by thiamine-deficient mothers.
  • References: [1,8,9,10,11,12,13]

Severe Vitamin B1 Deficiency (Beriberi) Symptoms and Signs

Early symptoms, such as weakness, nausea, tingling feet and fast heart beat can develop within 1 week to 1 month of reduced vitamin B1 intake.

Advanced vitamin B1 deficiency can cause:

  • Severe leg muscle weakness and cramps, which can prevent a person to walk, and bilateral, symmetrical feet and, later, hands tingling or pain (peripheral neuropathy, burning feet syndrome)
  • Leg swelling, increased heart rate, difficulty breathing and fatigue (congestive heart failure)
  • Wernicke’s encephalopathy, an acute brain damage with wide-based gait, apathy, insomnia, confusion or coma, which can cause death or can proceed to chronic Korsakoff psychosis with inability to remember new and past events (anterograde and retrograde amnesia) and making up facts (confabulation)
  • Often, even a person with severe vitamin B1 deficiency has no symptoms.

References: [1,8,15,34]

Diagnosis, Treatment and Prognosis

Vitamin B1 deficiency can be confirmed by a blood test. After a thiamine injection, symptoms usually improve within few hours and resolve completely within few days, but rarely in chronic Korsakoff psychosis [8]. Along with vitamin B1, other nutrients are often necessary:

  • In the UK, ampules for intramuscular or intravenous injections with vitamin B1 (thiamine), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B9 (folate) and vitamin C are often used.
  • In the US, a bag of intravenous fluids, called “banana bag,” or “rally pack,” containing vitamin B1 (thiamine), vitamin B9 (folate) and magnesium sulfate is often used [9].

Vitamin B1 Supplements

By mouth (available over-the-counter)


  • Thiamine mononitrate (TMN)
  • Thiamine hydrochloride (THCl)
  • Thiamine pyrophosphate (TPP)


Fat-soluble supplements provide higher blood thiamine concentrations than the water-soluble ones [31].

  • Thiamine propyl disulfide (TPD) or prosultiamine
  • Allithiamine naturally occurs in garlic; one of the synthetic forms is thiamine tetrahydrofurfuryl disulfide (TTFD) or fursultiamine
  • Sulbutiamine can reach the brain in much greater amounts than other thiamine supplements [17]. Some small studies have suggested sulbutiamine could reduce fatigue (asthenia) but more research is warranted [36].


Benfotiamine is a synthetic thiamine, poorly soluble in water and fat; it can provide higher blood thiamine concentrations than water- and lipid-soluble forms [37]. In two small studies, oral benfotiamine reduced pain in individuals with diabetic [32] or alcoholic neuropathy [35].

Available oral thiamine forms

Oral thiamine is available alone as capsules, tablets (10-500 mg), softgels, lozenges, powder, liquid or as part of B-complex or multivitamin supplements.

NOTE: From the current scientific evidence it is not yet possible to conclude which of the above thiamine supplements is most effective.

Intramuscular injection (shot) and intravenous infusion

A thiamine hydrochloride injection into a muscle or infusion into a vein is used to treat severe acute vitamin B1 deficiency.

Recommended Thiamine Replacement Dosage for Adults

Healthy individuals on regular diets, including infants, pregnant and breastfeeding women and vegans can get sufficient amounts of thiamine by eating variety of foods, so they do not likely need thiamine supplements.

For individuals with suspected or confirmed vitamin B1 deficiency, various medical experts recommend very different doses of thiamine supplements:

  • For mild deficiency without symptoms, tablets 5-30 mg/day [12]
  • For chronic alcoholics with increased risk to develop deficiency, tablets up to 50 mg/day [12,23] or, intramuscular injections, 250 mg/day for several days [26]
  • For a brain damage (Wernicke’s encephalopathy): intramuscular injections 15-300 mg/day or intravenous infusion 100-1,500 mg/day for few days, and then oral supplements 2.5-50 mg/day for several weeks until establishing the regular diet [25,26,38]
  • During alcohol withdrawal, intramuscular injections, 250 mg/day for 3-5 days [38]

Can vitamin B1 supplements be good for you?

Vitamin B1 supplements are effective in:

  • Vitamin B1 deficiency; in mild deficiency, vitamin B1 in the doses 10 mg/day may decrease fatigue, help to keep you awake and improve mood and energy [21,22].
  • Wernicke-Korsakoff syndrome
  • Genetic disorders in infants: Leigh’s disease, maple syrup urine disease, lactic acidosis associated with pyruvate carboxylase deficiency and hyperalaninemia [20,24]thiamine-responsive megaloblastic anemia (TRMA) [30]

Vitamin B1 supplements are possibly effective in:

  • Prevention of kidney damage in diabetes 2
  • Prevention of cataracts
  • Prevention of acute thiamine deficiency triggered by dextrose infusion or high-carbohydrate diet in a chronic alcoholic or malnourished person [16,29]

Source: Natural Medicines Comprehensive Database [12]

There is insufficient evidence about vitamin B1 supplements effectiveness in preventing or treatment of cancer, poor appetite, ulcerative colitis, Crohn’s disease, chronic diarrhea, HIV/AIDS, candida infections, congestive heart failure — CHF (except when caused by vitamin B1 deficiency), poor circulation, high blood pressure, atherosclerosis in diabetes mellitus, megaloblastic anemia (except in the thiamine-responsive type), blood clots, painful menstruation, multiple sclerosis, Alzheimer’s disease (dementia), Bell’s palsy, epilepsy, optic neuropathy, sciatic pain, cerebellar ataxia (muscle incoordination) after fever, memory loss, tinnitus, erectile dysfunction/low libido, DIDMOAD (Wolfram) syndrome, leg cramps in pregnancy, rheumatism (joint pain), gout, temporomandibular joint (TMJ) disorder, asthenia, fibromyalgia, chronic fatigue syndrome (CFS), low back pain, insomnia, stress, aging, canker sores, depression, stuttering or pyruvate dehydrogenase deficiency; its effectiveness in improving athletic performance, weight loss or as a mosquito repellent has also not been proven [1,6,12,24,33].

Vitamin B1 supplements probably do not help in hip fractures, skin disorders, nerve repair in peripheral neuropathy (except when caused by vitamin B1 deficiency) or hangover (which is not associated with vitamin B1 deficiency, so there is no reason why vitamin B1 patch should work) [12].

Can vitamin B1 supplements be bad for you? Side Effects, Risks

In general, thiamine supplements are safe to use. No side effects have been reported even after very high doses (1,500 mg of thiamine by mouth), so overdose is practically impossible [31]. Excessive thiamine is lost with urine. No tolerable upper intake level (UL) for thiamine has been set [1].

Vitamin B1 toxicity. In few cases, severe allergic reactions (anaphylactic reactions with itchy skin, swollen face, difficult breathing, low blood pressure or even death) occurred after repeated intravenous infusions but not after oral intake [28].

Thiamine safety in pregnancy

The U.S. Food and Drug Administration (FDA) lists thiamine in doses within Recommended Daily Allowance (1.4 mg/day) as pregnancy category A, which means no harm for the babies in human trials have been observed, and doses above 1.4 mg/day as category C, because insufficient human studies have been done to prove its safety at these doses [18,23]. In conclusion, thiamine in pregnancy should be used only when the deficiency is suspected.

Vitamin B1 Interactions With Drugs and Foods

The following medications can lower the blood concentration of thiamine: antacids, diuretics, the prolonged use of the anticonvulsant phenytoin, birth control pills, certain antibiotics, sulfa drugs and the chemotherapeutics 5-fluorouracil and methotrexate [1,8].

Alcohol and anti-thiamin factors in foods, like raw freshwater fish, raw shellfish, ferns, African silkworms (in Nigeria), areca (betel) nuts, horsetail, when consumed in large amounts, can inhibit thiamine absorption [1,19].

Folate and magnesium deficiency, which are both common in alcoholics, reduce thiamine activity in the body [1,8].

Glucose infusion may, in alcoholics or individuals after prolonged starvation, trigger acute vitamin B1 deficiency (Wernicke encephalopathy), a part of refeeding syndrome.

Vitamin B1 Absorption and Body Stores

  • Site of absorption: mainly in the upper small intestine (jejunum)
  • Vitamin B1 is a water-soluble vitamin, which does not dissolve in the body fat, so the body stores are depleted within 1 month of cessation of the vitamin intake.
  • References: [1,8]

Frequently Asked Questions

1. What are thiamine mechanism of action and main functions ?

Thiamine acts as an activating molecule (cofactor, coenzyme) for the enzymes involved in the breakdown of carbohydrates and proteins and thus enables the release of energy from them [1]. Thiamine is especially important for proper functioning of the nerves, brain, muscles and heart. Thiamine is also involved in the production of gastric acid, neurotransmitters GABA and acetylcholine, maintaining the myelin nerve sheaths and in breakdown of alcohol.

2. Which vitamin gives you more energy: B1, B6 or B12?

Vitamins B1, B6 and B12 do not give you energy because they do not contain calories but make your body able to produce energy. When you are deficient in vitamin B1, B6 or B12, your body is less able to produce energy so appropriate vitamin B supplements will restore this ability, but when you have normal blood levels of these vitamins, vitamin B supplements will not likely boost your energy.

3. What are the benefits of high-dose thiamine supplements?

  • High thiamine doses in the form of intramuscular or intravenous injection are necessary to provide high concentrations of thiamine in the brain in treatment of acute brain damage caused by severe thiamine deficiency [26].
  • High doses (>300 mg/day) of oral benfotiamine have been reported to be more effective in treatment of peripheral neuropathy than lower doses (150 mg/day) [17].

4. Does vitamin B1 cause yellow urine?

It is not vitamin B1 but vitamin B2 (riboflavin) (and beta-carotene and vitamin C), which gives the urine bright yellow color [2].

  1. Vitamin B1 or thiamine overview: definition, best sources, importance for health  Linus Pauling Institute
  2. Vitamin B2 or riboflavin properties  Linus Pauling Institute
  3. RDA for vitamins and minerals  Institute Of Medicine
  4. Thiamine mononitrate for food fortification: origin, safety  Food and Drug Administration
  5. Foods containing vitamin B1  USDA.gov
  6. Thiamine for prevention and treatment of Wernicke’s Korsakoff syndrome  Cochrane.org
  7. Rice processing  Usaemergencysupply
  8. Vitamin B1 deficiency–dry, wet and cerebral beriberi–symptoms and signs  Emedicine
  9. Wernicke encephalopathy treatment  Emedicine
  10. Micronutrient deficiencies after bariatric surgery  PubMed
  11. Diabetes and thiamine deficiency  PubMed
  12. Thiamine overview, indications for use  Therapeuticresearch
  13. Vitamin B1 deficiency risks  Mayo Clinic
  14. Brewer’s yeast nutrition facts NutritionData
  15. Alcohol withdrawal complications  National Institute of Health
  16. Importance of administration of thiamine before dextrose  Lww.com
  17. Effectiveness of benfotiamine in treating pain in diabetic neuropathy  PubMed
  18. Pregnancy categories of common drugs and supplements  PubMed Central
  19. Antithiamine factors  Healthline
  20. Thiamine and gastric acid  Healthline
  21. Effect of thiamine supplements on energy and mood in women  PubMed
  22. Effect of thiamine supplements on mood in elderly  AJCN.nutrition.org
  23. Recommended thiamine doses  Mayo Clinic
  24. Evidence about vitamin B1 health benefits  Mayo Clinic
  25. Vitamin B1 deficiency treatment  Emedicine
  26. Thiamine doses  Todaysdietitian
  27. List of GRAS substances  U.S. Food and Drug Administration
  28. Side effects of too much thiamine  Drugs.com
  29. Refeeding syndrome  Hopkinsmedicine
  30. Thiamine-responsive megaloblastic anemia  National Institute of Health
  31. Absorption of high-dose oral thiamine hydrochloride  Biomedcentral
  32. Benfotiamine and pain in diabetic neuropathy  PubMed
  33. Allithiamine and muscle performance  PubMed
  34. The role of thiamine deficiency in brain disease  National Institute of Health
  35. Effect of benfotiamine in alcoholic neuropathy  PubMed
  36. Sulbutiamine properties  PubMed
  37. Thiamine derivatives overview  PubMed Central
  38. Alcohol withdrawal treatment  Patient.info
  39. B vitamins in breast milk  PubMedCentral
  40. Do breastfeed infants need supplemental vitamins?  PubMed

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