How much thiamin (B1) do you need per day?

The RDA for thiamin is 1.2 mg a day for men and 1.1 mg for women aged 19 to 50.

These are the reference amounts used on US food labels and in dietary guidance, not personal targets. What you need shifts with age, pregnancy, medication and health conditions. The % Daily Value shown on every food page here is calculated against the FDA Daily Value for thiamin (B1), which is 1.2 mg a day.

What this means for you

A little over a milligram a day, and whole grains, pork, legumes, seeds and fortified flour supply it without any planning. No upper limit was set, because high intakes have not been shown to cause harm.

One thick pork chop, about 180 grams of lean meat, carries 1.2 mg on its own. That is the entire Daily Value printed on labels, from one piece of meat.

For most people that is the whole story. The reason this page exists is a different one.

Not for everyone. In wealthy countries, long-term alcohol use disorder is the most common cause of thiamin deficiency. In that situation thiamin is a medical treatment rather than a supplement choice, because untreated deficiency damages the brain and nerves in ways that do not fully reverse.

Thiamin runs on a short reserve. The body stores only a few weeks' worth, which is why deficiency can appear quickly when eating stops or absorption fails, and why it turns up after bariatric surgery, during prolonged vomiting in pregnancy, and in intensive care.

One medicine is worth naming. The diuretic furosemide increases thiamin loss in urine, and levels have been measured falling into the deficient range in people taking it long-term.

Whether you are short depends on which yardstick someone picked

Headlines about thiamin shortfall are built on a choice most of them do not mention. In the 2021 to 2023 national survey, American adults took in a median of 1.31 mg a day, 1.50 for men and 1.16 for women. Held against the 1.2 mg Daily Value on labels, 42.9 per cent came up short, and among women it was 52.6 per cent. Held against the requirement the Daily Value is actually built out of, 26.6 per cent of women aged 19 to 30 came up short, and 29.7 per cent of men the same age.

Same people. Same food. One number is nearly double the other. The Daily Value is set high on purpose, so that a label covers almost everybody including the people who need the most, which means landing below it is ordinary rather than a finding about you.

A bigger dose does not do more, and that has been tested twice

Myth. More thiamin works better. Where thiamin is given as a medicine, this was tested head on. Three hundred and ninety-three patients at risk of Wernicke's encephalopathy took 100 mg a day, 100 mg three times a day, or 300 mg three times a day for three days. A further 127 who already had symptoms took 100, 300 or 500 mg three times a day for five days. That is a fifteen-fold spread of dose, and it made no difference to cognition, to eye signs, to unsteadiness or to confusion.

Established. The same shape turns up in nursing mothers. In Cambodia, where infant beriberi still kills, mothers took 1.2, 2.4 or 10 mg of thiamine a day from two weeks after the birth. The thiamine in their milk came out at 183, 190 and 206 micrograms per litre against 153 on placebo. All three beat placebo. None of them beat each other. The modelled dose that gets you 90 per cent of the way was 2.35 mg a day, with a range from 0.58 to 7.01, which is a wide range around a small number.

The form on the box moves the blood level more than the dose does

Here is the strange part. The milligrams barely matter, and the word next to them matters a lot. Ordinary thiamine hydrochloride dissolves in water, and the gut lets only so much through however much you swallow. The fat-soluble precursors get past that ceiling. In healthy volunteers, benfotiamine delivered about eleven times the plasma thiamine of thiamine hydrochloride, and roughly twice the thiamine diphosphate inside red blood cells.

That has been checked by other people. An independent crossover study in Korean volunteers found a fat-soluble derivative giving more than three times the plasma thiamine of plain thiamine nitrate. And with the dose pinned at 100 mg for all three, benfotiamine came out ahead of both alternatives on every measure taken, while thiamine disulfide came last.

Unsettled. What nobody has shown is that the higher blood level makes anyone better. The bioavailability studies were done in healthy volunteers and measured thiamine, not health. Set that against the dose trial above, where a fifteen-fold difference in dose changed nothing a doctor could measure, and the reasonable guess is that once you have enough, more of it in the blood buys nothing. Reasonable guess is all it is. If a shop assistant tells you benfotiamine is the better one, the blood data are on their side and the outcome data do not exist.

The practical version is short. Aim at the requirement and take it from food. If you have a reason to think you need more than that, the reason is the part to take to a doctor, and the size of the tablet is the least interesting thing in the conversation.

What thiamin gets sold for, and where those claims stand

Unsettled. Thiamin for heart failure has now been pooled twice, and the two reviews disagree in an uncomfortable place. The first, seven trials in 274 people, found no gain in how the heart pumped but reported that the supplement did correct a deficiency where one existed. The second, eight trials in 384 people, found no benefit on anything it measured, and thiamine status was on that list. Ejection fraction came out at a mean difference of -0.19, with a confidence interval from -2.78 to 0.96. Symptom class, BNP and quality of life were unchanged. So two pooled analyses of the same literature now disagree about whether thiamin even fixes the deficiency it is prescribed for. Neither of them found it helps the heart, and that part is not in doubt.

Myth. Thiamin helps stuttering. It is sold for that. A 2025 systematic review searched for the evidence across 39 studies, 17 drug classes and four dietary treatments, and filed thiamine under insufficient evidence, alongside copper, green tea and Ayurvedic supplements.

In diabetes, a 2025 review of seven clinical studies found the results conflicting and the trials too small to settle anything. The case for thiamin remains the deficiency itself, and in wealthy countries that mostly means alcohol.

If you have seen thiamin recommended for heart failure or diabetes, both claims have now been tested. Seven randomised trials in 274 people with chronic heart failure found no gain in how the heart pumped, although the supplement did correct a deficiency where one existed. In diabetes, a 2025 review of seven clinical studies found the results conflicting and the trials too small to settle anything. The case for thiamin remains the deficiency itself, and in wealthy countries that mostly means alcohol.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Foods highest in thiamin (B1) on this site

• Bacon, meatless fortified — 6.34 mg per 1 cup (528% DV)
• Corn flour, masa, white fortified — 1.68 mg per 1 cup (140% DV)
• Chicken, meatless, breaded, fried fortified — 1.66 mg per 1 cup, diced (138% DV)
• Sesame seed kernels, toasted — 1.54 mg per 1 cup (129% DV)
• Meatballs, meatless fortified — 1.35 mg per 1 cup (113% DV)

All thiamin (B1) sources ranked →

Full guide: Thiamin: a deficiency that is mostly about alcohol, not about diet