Vitamin B1 (thiamin): how much you need by age, benfotiamine vs thiamin, and who runs low

Written by the ASDHelp research team · Last reviewed 22 October 2026

Thiamin forms at a glance

	Thiamin hydrochloride or mononitrate	Benfotiamine	TTFD (allithiamine type)
What it is	The most common forms in supplements; stable and water soluble (NIH ODS)	A synthetic thiamin derivative; not water soluble; the body converts it to thiamin (NIH ODS)	A synthetic counterpart of allithiamine, a disulfide form of thiamin made in garlic when it is cut or crushed (Lonsdale 2004)
How it is absorbed	Active transport at food-level doses, passive diffusion at high doses (NIH ODS)	Peak blood thiamin about 5 times higher than with thiamin hydrochloride (Loew 1996)	No human absorption data in the sources used here
Typical use	Multivitamins, B-complexes, thiamin-only products	Some B-complexes and stand-alone products	Specialty products
Upper limit	None set for thiamin; the Food and Nutrition Board noted that very large intakes could still have adverse effects (NIH ODS)

Source: NIH Office of Dietary Supplements; PubMed records under Sources.

What does vitamin B1 do in the body?

Thiamin, also spelled thiamine, is one of the water-soluble B vitamins. It plays a central role in energy metabolism, and through that in the growth, development and function of cells (NIH Office of Dietary Supplements).

An adult body holds only about 25 to 30 mg of thiamin in total. About 80% of it is thiamin diphosphate (TDP, also called thiamin pyrophosphate), the main working form. TDP is a cofactor, a helper molecule, for five enzymes that handle glucose, amino acids and fats. The liver keeps a small reserve, and thiamin has a short half-life, so the body needs a steady supply from food every day (NIH ODS).

Thiamin works alongside the other B vitamins in energy metabolism. If you are reading about the B group as a whole, our pages on vitamin B2 and vitamin B6 cover two of its partners.

How much vitamin B1 do children and adults need?

The Food and Nutrition Board sets a Recommended Dietary Allowance (RDA) for thiamin from age 1. For babies it sets an Adequate Intake (AI) equal to what healthy breastfed infants take in. The Daily Value on US labels is 1.2 mg for adults and children aged 4 and older.

Age	Male	Female	Pregnancy	Lactation	Upper limit (UL)
Birth to 6 months (AI)	0.2 mg	0.2 mg			Not set
7 to 12 months (AI)	0.3 mg	0.3 mg			Not set
1 to 3 years	0.5 mg	0.5 mg			Not set
4 to 8 years	0.6 mg	0.6 mg			Not set
9 to 13 years	0.9 mg	0.9 mg			Not set
14 to 18 years	1.2 mg	1.0 mg	1.4 mg	1.4 mg	Not set
19 to 50 years	1.2 mg	1.1 mg	1.4 mg	1.4 mg	Not set
51 years and older	1.2 mg	1.1 mg			Not set

Source: NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals (Table 1).

Most people in the United States already get enough. In national survey data from 2003 to 2006, only 6% of people had a usual thiamin intake below the average requirement. From food alone, children aged 2 to 5 average 1.27 mg a day, children aged 6 to 11 average 1.54 mg, and teens aged 12 to 19 average 1.68 mg. Adult men average 1.95 mg and women 1.39 mg from food; with supplements, men average 4.89 mg and women 4.90 mg (NIH ODS). If your child takes a supplement, the dose belongs to their pediatrician, who can weigh it against what your child already eats.

Which foods are high in thiamin?

Whole grains, meat and fish carry thiamin naturally, and breads, cereals and infant formulas in the United States are fortified with it. Cereals and bread are the most common sources in the US diet, and pork is another major one. Dairy foods and most fruits contain little. About half of the thiamin Americans eat comes from fortified foods (NIH ODS). Some examples from the NIH food table:

• Breakfast cereal fortified with 100% of the Daily Value, 1 serving: 1.2 mg
• Egg noodles, enriched, cooked, 1 cup: 0.5 mg
• Pork chop, broiled, 3 ounces: 0.4 mg
• Trout, cooked, 3 ounces: 0.4 mg
• Black beans, boiled, ½ cup: 0.4 mg
• Mussels, cooked, 3 ounces: 0.3 mg
• Brown rice, not enriched, ½ cup: 0.2 mg
• Whole wheat bread, 1 slice: 0.1 mg
• Sunflower seeds, 1 ounce: 0.1 mg

Cooking matters. Bread has 20% to 30% less thiamin than its raw ingredients, and pasteurization lowers the small amount in milk by up to 20%. Because thiamin dissolves in water, a good share is lost when cooking water is poured away. White rice that is not enriched has one-tenth the thiamin of brown rice (NIH ODS). Using the cooking liquid in soups and sauces keeps more of it.

Is benfotiamine better than regular thiamin?

Benfotiamine is absorbed differently, and the studies show it raises blood thiamin more than thiamin hydrochloride taken by mouth. Whether that matters depends on why someone is taking it.

• A 1996 review of absorption studies found that peak plasma thiamin was about 5 times higher after benfotiamine than after thiamin hydrochloride, and bioavailability was at most about 3.6 times higher (Loew 1996, PMID 8929745).
• A 2014 study in healthy volunteers measured plasma thiamin at 1147.3 ± 490.3% of the level reached with thiamin hydrochloride, while TDP inside red blood cells, the working form, reached 195.8 ± 33.8%, or about 2 times. Converting benfotiamine to thiamin produced large amounts of hippuric acid in urine, which did not build up with repeated doses (Xie 2014, PMID 24399744).

Regular thiamin is absorbed well too. In a randomized crossover study in healthy adults, single oral doses of 100 mg, 500 mg and 1500 mg of thiamin hydrochloride raised blood levels quickly. The rise was not proportional to the dose: the biggest gains per milligram came at the lowest dose, because an active carrier works at small doses and passive diffusion carries the rest (Smithline 2012, PMID 22305197).

For meeting the RDA, the ordinary forms in a multivitamin or B-complex are enough. The higher-dose derivatives are a question for a clinician who knows why a larger amount is wanted.

Can you take too much vitamin B1?

No upper limit has been set. The Food and Nutrition Board found no reports of adverse effects from high thiamin intakes of 50 mg a day or more from food or supplements. Its explanation is that absorption drops quickly once intake goes above about 5 mg, and the body passes extra thiamin in urine (NIH ODS).

The Board still noted that very large intakes could have adverse effects that have not been reported. No limit is not the same as proof that any dose is useful. Most single-nutrient and B-complex products give many times the RDA, so if you combine products, add up the total and bring that number to your doctor.

Who is more likely to run low on thiamin?

A shortfall is uncommon in people who eat a varied diet with fortified grains. The NIH fact sheet lists groups who are more likely to run low:

• People who drink alcohol heavily. Up to 80% of people with chronic alcohol dependence develop thiamin deficiency, because ethanol reduces absorption, liver stores and the conversion of thiamin to its working form (NIH ODS).
• Older adults. Up to 20% to 30% of older adults have lab results that suggest some degree of deficiency, linked to low intake, several medications at once and lower absorption with age (NIH ODS).
• People who have had weight-loss surgery. A systematic review found 84 published cases of Wernicke encephalopathy, a severe thiamin deficiency affecting the brain, after bariatric surgery. Most (94%) came within 6 months of the operation, and frequent vomiting was present in 90%. About half (49%) did not fully recover (Aasheim 2008, PMID 18948797). Supplements that include thiamin are almost always recommended after these operations (NIH ODS).

Early signs of a shortfall named by NIH include loss of appetite and weight, confusion, short-term memory problems, muscle weakness and heart symptoms. These signs have many possible causes, so they are a reason to see a doctor and get tested, not a reason to start a supplement on your own.

How thiamin status is tested

Blood thiamin alone is not a reliable guide. A common test measures the activity of transketolase, an enzyme in red blood cells that depends on TDP, with and without added TDP. The difference, called the TDP effect, is usually 0% to 15% in healthy people, 15% to 25% with a marginal shortfall, and higher than 25% with deficiency. Urine thiamin reflects recent intake rather than stores: in adults, less than 100 mcg a day suggests low intake and less than 40 mcg a day very low intake (NIH ODS). Your doctor can decide which test fits and how to read it.

Does thiamin interact with medicines?

Thiamin is not known to change how any medicine works, but some medicines can lower thiamin levels (NIH ODS):

• Furosemide. This loop diuretic increases thiamin loss in urine. In one study of 32 adults taking furosemide every day, lab signs of severe thiamin deficiency were found in 24 of 25 people (98%) on 80 mg a day or more, and in four of seven (57%) on 40 mg a day (Zenuk 2003, PMID 14712323).
• Fluorouracil (5-fluorouracil). Case reports describe severe thiamin deficiency during treatment with this drug, possibly because it increases thiamin metabolism and blocks formation of TDP (NIH ODS).

If you or your child take either medicine regularly, ask the prescriber whether thiamin status should be checked. Do not change a medicine dose on your own.

Which ASDHelp products contain thiamin?

Doses are copied from each label. There is no upper limit for thiamin, but every product below gives more than the RDA and more than the 5 mg point where absorption starts to level off. If you use more than one product, add up the total.

• Spectrum B Complex + Benfotiamine: 20 mg of thiamin (as thiamine HCl) plus 20 mg of benfotiamine per capsule, with the other B vitamins. Label directions: 1 capsule once or twice daily; no children's dose.
• Formula C: 25 mg of thiamin per 6 capsules, in a broad multivitamin and mineral formula. Label directions: adults and children 4 years and older, 6 capsules daily with food; under 4, as directed by a healthcare professional.
• Spectrum Formula Chewable + Iron: 5 mg of thiamin (as thiamine HCl) per 4 chewable tablets, in a multivitamin with 3 mg of iron. Label directions: ages 1 to 3, 1 to 2 tablets twice daily; 4 and older, 2 to 4 tablets twice daily. Keep it out of children's reach because it contains iron.
• MITOboost Protein Powder Strawberry: 15 mg of thiamin per scoop (29.6 g), with rice protein and other nutrients. Label directions: 1 scoop once daily in 8 to 10 ounces of liquid; no children's dose.

For a child, the pediatrician should choose the product and the dose.

Questions to take to your doctor

• Based on what we eat, especially grains, beans and meat, are we likely to fall short of the thiamin RDA?
• Do any of my medicines, such as furosemide, affect thiamin, and should my status be tested?
• If a test is useful, which one: the transketolase test or urine thiamin?
• If I take a B-complex and a multivitamin, how much thiamin am I getting in total, and is benfotiamine needed at all?

Sources

• NIH Office of Dietary Supplements. Thiamin: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Thiamin-HealthProfessional/
• Smithline HA, Donnino M, Greenblatt DJ. Pharmacokinetics of high-dose oral thiamine hydrochloride in healthy subjects. BMC Clin Pharmacol. 2012. PubMed 22305197
• Loew D. Pharmacokinetics of thiamine derivatives especially of benfotiamine. Int J Clin Pharmacol Ther. 1996. PubMed 8929745
• Xie F, et al. Pharmacokinetic study of benfotiamine and the bioavailability assessment compared to thiamine hydrochloride. J Clin Pharmacol. 2014. PubMed 24399744
• Lonsdale D. Thiamine tetrahydrofurfuryl disulfide: a little known therapeutic agent. Med Sci Monit. 2004. PubMed 15328496
• Aasheim ET. Wernicke encephalopathy after bariatric surgery: a systematic review. Ann Surg. 2008. PubMed 18948797
• Zenuk C, et al. Thiamine deficiency in congestive heart failure patients receiving long term furosemide therapy. Can J Clin Pharmacol. 2003. PubMed 14712323

These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. This article is educational and is not medical advice.