Does vitamin B1 (thiamine) help with sleep?

Not on current evidence. The few hints of a benefit come from people who were short of it or who took it with vitamin B2. A 2025 meta-analysis of 28 randomized supplement trials credited better sleep to tryptophan, vitamin D, omega-3, zinc and antioxidants, and thiamine was not among them. We read only its abstract, so we could not check whether any B vitamin trial sat inside its pooled vitamin group.

Unsettled. We found no meta-analysis of thiamine for sleep and no randomized trial of thiamine alone with sleep as its main outcome. What exists is one small trial of B1 combined with B2, two older trials where sleep improved only as a trend, and one survey. That is too little to say thiamine works for sleep. It is also too little to say it does not.

Sleep quality score (PSQI) in one trial of 43 adults

Group means at the start and after four weeks. The two groups did not start level, and the supplement always combined vitamin B1 with vitamin B2, so the chart cannot show what thiamine does alone. No intervals are drawn. Source: card ev-b1sl-02 below.

What the trials found

Vitamin B1 together with B2

In a 4-week randomized trial in 43 adults, 100 mg of vitamin B1 plus 100 mg of vitamin B2 a day lowered the sleep quality score (PSQI) from 8.0 to 6.3. In the placebo group it worsened from 5.7 to 7.4. Daytime sleepiness on the Epworth scale fell from 13.0 to 9.1 with the vitamins, and anxiety did not improve. The groups started at different scores, the trial was small and short, and thiamine was never given alone, so the effect of B1 by itself is unknown.

Thiamine alone, in older people with low levels

In a 6-week randomized trial in 80 older Irish women from a population with marginal thiamine deficiency, 10 mg of thiamine a day tended to reduce daytime sleep and improve sleep patterns. The abstract reports this as a tendency and gives no numbers for sleep. In a second placebo-controlled trial in people aged 65 and over with low thiamine, 10 mg a day helped only those whose levels stayed low. For sleep and energy the benefit did not reach significance (P = 0.07).

Thiamine intake and sleep in surveys

In 15,384 Korean adults aged 19 to 64, the lowest quarter of thiamine intake was linked with 49 per cent higher odds of sleeping too long than the highest quarter (OR 1.49, 95% CI 1.16 to 1.91). Among high-risk drinkers the odds ratio was 1.78 (95% CI 1.28 to 2.49). These are odds, not risks, from self-reported diet and sleep at one point in time. The survey says nothing about insomnia or about supplements.

Odds of sleeping too long by thiamine intake, 15,384 Korean adults

Observational data

Odds ratios with 95 percent confidence intervals from one cross-sectional survey with self-reported diet and sleep. They describe an association with oversleeping, not insomnia, and not an effect of supplements. The survey's absolute numbers are not in what we read. Source: card ev-b1sl-06 below.

A 2017 systematic review of 26 studies on micronutrients and sleep, with searches up to January 2016, linked sleep duration with iron, zinc, magnesium, copper, potassium and vitamin B12. It did not name thiamine.

Who should be careful

The NIH Office of Dietary Supplements notes that no upper limit has been set for thiamine, because no adverse effects have been reported at 50 mg a day or more. That is an absence of reports, and it does not prove safety at any dose.

Not for everyone. Some people do run short of thiamine, and poor sleep is not how it shows. NIH notes up to 80 percent of people with chronic alcoholism develop thiamine deficiency. Bariatric surgery can cause severe deficiency through malabsorption, leading to beriberi or Wernicke's encephalopathy. The diuretic furosemide is linked to thiamine loss in urine, possibly to deficient levels, and whether supplements prevent that is not established. If any of these apply to you, low thiamine is a question for the person treating you.

NIH lists weight loss, loss of appetite, confusion and short-term memory loss among the early signs of deficiency, and its fact sheet does not mention sleep. A 2026 meta-analysis of 12 observational studies with 5,510 people with Wernicke encephalopathy found alcohol was the main risk factor, at 90.7 percent. Among the other cases the most frequent settings were malnutrition (30.2 percent), infections (25.1 per cent) and psychiatric disorders (15.4 percent).

High doses given in hospital are a separate matter from a sleep supplement. In a meta-analysis of 35 studies with 3,494 critically ill patients, intravenous thiamine did not clearly lower mortality (RR 0.89, 95% CI 0.75 to 1.06, low certainty). It lengthened the stay in intensive care by 0.40 days (95% CI 0.01 to 0.79, high certainty). We hold only the relative figure for mortality, without absolute numbers.

What expert bodies say

We found no agency guidance on thiamine for sleep. The NIH Office of Dietary Supplements fact sheet on thiamine has no passage on sleep at all. We did not check the EU register of health claims for this page.

How we searched

Searched: a local copy of PubMed, queried on 7 October 2026 for thiamine, vitamin B1 or benfotiamine with sleep, insomnia, sleep quality, drowsiness or fatigue (60 results). We also queried B vitamins or B complex with sleep (13, none about thiamine with a sleep outcome). Further queries covered reviews of thiamine in Wernicke encephalopathy and alcohol use (25) and thiamine with delirium, restless legs, sleep apnoea, melatonin or circadian terms (59). We searched the NIH thiamine fact sheet for sleep and found nothing. The web, Europe PMC and ClinicalTrials.gov were searched too. Every study used was checked against Retraction Watch, and none was retracted.

Included: one meta-analysis of supplement trials for sleep, one systematic review of micronutrients and sleep, three randomized trials, one national survey, one meta-analysis of intravenous thiamine in intensive care, one meta-analysis of Wernicke encephalopathy and five passages of the NIH fact sheet.

Excluded: a case report where thiamine was given with chlordiazepoxide, so its effect could not be separated. Trials of thiamine for fatigue in bowel disease and chronic fatigue, which did not measure sleep. A trial of B1 and B6 added to lithium with no sleep outcome in its abstract, and a product combining B vitamins with magnesium. We also left out a post-COVID thiamine trial for which we could confirm no PubMed or DOI record.

What we read: abstracts for all studies, and the relevant sections of the NIH fact sheet.

What we could not get: the full texts of the two older trials in older adults, whose abstracts report sleep only as a trend without numbers, and the full text of the 2025 meta-analysis.

What would change this answer

A randomized trial of thiamine alone with sleep as its main outcome, ideally in people whose thiamine was measured and found low. We found none.
Results from a trial registered on ClinicalTrials.gov that compares melatonin with 100 mg of thiamine at night for REM sleep in hepatic encephalopathy. It is recruiting and has no results yet.
A check of the 2025 meta-analysis full text, to see whether any B vitamin trial sits inside its pooled vitamin results.

The rest of the nutrient, in one place. Thiamin: a deficiency that is mostly about alcohol, not about diet → What it does, how much you need, who runs short, and what too much does, with the evidence level shown on every line.

The full guide

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

The same question for other foods (sleep)

Sources

ev-b1sl-01 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs · n = 28 trials
These findings suggest that tryptophan, vitamin D, omega-3, zinc, and antioxidants may enhance sleep quality by decreasing SL, and WASO increases SE and extends TST, respectively.
Who: populations with sleep disorders and healthy individuals in randomized trials of dietary supplements
Effect: pooled supplements: PSQI MD -0.70 (95% CI -1.37 to -0.03); sleep latency SMD -0.24 (-0.37 to -0.10); no thiamine-specific estimate
Certainty: full text not read; whether any B-vitamin trial was pooled under 'vitamins' not checked
Nutrients, 2025 · checked 2026-10-07 · we read the abstract
ev-b1sl-02 · Randomized controlled trial(s) · parallel randomized double-blind placebo-controlled trial · n = 43
The PSQI scores decreased in the supplement group from 8.0 ± 3.12 to 6.3 ± 2.0 (p < 0.05), while the placebo group worsened from 5.7 ± 2.7 to 7.4 ± 2.9.
Who: adults randomized to 100 mg vitamin B1 and 100 mg vitamin B2 daily or placebo for four weeks
Effect: PSQI 8.0 to 6.3 (supplement, p < 0.05) vs 5.7 to 7.4 (placebo); groups unequal at baseline
Certainty: B1 always combined with B2, so the effect of thiamine alone is unknown; small and short; baseline PSQI differed
Nutrients, 2025 · checked 2026-10-07 · we read the abstract
ev-b1sl-03 · Randomized controlled trial(s) · parallel randomized double-blind placebo-controlled trial · n = 43
Meanwhile, the ESS scores in the supplement group decreased from 13.0 ± 3.4 to 9.1 ± 3.9 (p < 0.05), demonstrating a significant improvement compared to the placebo group.
Who: adults randomized to 100 mg vitamin B1 and 100 mg vitamin B2 daily or placebo for four weeks
Effect: ESS 13.0 to 9.1 (p < 0.05); anxiety (SAS) no significant effect
Certainty: combined B1 and B2 product
Nutrients, 2025 · checked 2026-10-07 · we read the abstract
ev-b1sl-04 · Randomized controlled trial(s) · double-blind randomized placebo-controlled trial · n = 80
Thiamin supplementation also tended to reduce daytime sleep time, improve sleep patterns, and increase activity.
Who: healthy elderly Irish women from a population with marginal thiamin deficiency; thiamin 10 mg daily or placebo for 6 weeks
Effect: trend only: less daytime sleep, better sleep patterns; significant gains in appetite, energy intake, weight, well-being and less fatigue
Certainty: sleep result reported as a tendency without numbers; benefit tied to marginal deficiency
J Gerontol, 1991 · checked 2026-10-07 · we read the abstract
ev-b1sl-05 · Randomized controlled trial(s) · randomized double-blind placebo-controlled trial · n = 76
There was a trend toward benefits in sleep and energy (P = 0.07).
Who: people aged 65 or over with low erythrocyte thiamine pyrophosphate, oral thiamine 10 mg/d or placebo
Effect: sleep and energy: trend, P = 0.07; quality of life improved P = 0.02 in persistently low TPP group
Certainty: sleep was not significant; small subgroups (35 persistently low)
Am J Clin Nutr, 1997 · checked 2026-10-07 · we read the abstract
ev-b1sl-06 · Observational data · cross-sectional analysis of a national survey · n = 15,384
Low thiamine intake was associated with oversleeping (Q3: odds ratio [OR], 1.06; 95% confidence interval [CI], 0.86 to 1.32; Q2: OR, 1.24; 95% CI, 0.99 to 1.55; Q1: OR, 1.49; 95% CI, 1.16 to 1.91) and showed a significant trend for higher ORs at lower intake levels (p-trend<0.001).
Who: participants aged 19-64, Korea National Health and Nutrition Examination Survey 2012-2016
Effect: oversleeping Q1 vs highest quartile OR 1.49 (95% CI 1.16 to 1.91); high-risk alcohol use Q1 OR 1.78 (1.28 to 2.49)
Certainty: cross-sectional, FFQ and self-reported sleep; says nothing about insomnia or supplements
J Prev Med Public Health, 2022 · checked 2026-10-07 · we read the abstract
ev-b1sl-07 · Observational data · systematic review of experimental and observational studies · n = 26 articles
Micronutrient status has also been linked to sleep duration, with sleep duration positively associated with Fe, Zn and Mg levels, and negatively associated with Cu, K and vitamin B12 levels.
Who: experimental and observational studies of dietary or circulating micronutrients and sleep, infants to older adults
Effect: no thiamine finding reported
Certainty: search through January 2016
Public Health Nutr, 2017 · checked 2026-10-07 · we read the abstract
ev-b1sl-08 · Meta-analysis or systematic review · systematic review and meta-analysis of RCTs with GRADE · n = 3,494
Conversely, thiamine administration resulted in a slight increase in the length of ICU stay (MD, 0.40 days; 95% CI, 0.01-0.79 days; High CoE).
Who: critically ill patients in randomized trials of thiamine administration
Effect: mortality RR 0.89 (95% CI 0.75 to 1.06), low certainty; ICU stay MD +0.40 days (0.01 to 0.79), high certainty
Certainty: hospital IV doses, not oral supplements for sleep
Clin Nutr, 2024 · checked 2026-10-07 · we read the abstract
ev-b1sl-09 · Observational data · systematic review and meta-analysis of observational studies · n = 5,510
Alcohol consumption was the main risk factor (90.7%); among non-alcohol-related cases, the most frequent clinical settings were malnutrition (30.2%), infections (25.1%), and psychiatric disorders (15.4%).
Who: patients with Wernicke encephalopathy in observational studies
Effect: alcohol main risk factor 90.7%; non-alcohol cases: malnutrition 30.2%, infections 25.1%, psychiatric disorders 15.4%; mortality 5.1%
Certainty: pooled proportions, not an effect of thiamine
Neuroepidemiology, 2026 · checked 2026-10-07 · we read the abstract
ev-b1sl-10 · Position of an expert body · agency fact sheet · n = —
Because of the lack of reports of adverse effects from high thiamin intakes (50 mg/day or more) from food or supplements, the FNB did not establish ULs for thiamin [7].
Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
Effect: no UL; no adverse effects reported at 50 mg/day or more
Certainty: Absence of reports, not proof of safety at any dose.
NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
ev-b1sl-11 · Position of an expert body · agency fact sheet · n = —
Research has linked the use of furosemide to decreases in thiamin concentrations, possibly to deficient levels, as a result of urinary thiamin loss [49,58,59].
Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
Effect: furosemide lowers thiamin concentrations via urinary loss
Certainty: Whether supplements prevent it is not established.
NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
ev-b1sl-12 · Position of an expert body · agency fact sheet · n = —
Up to 80% of people with chronic alcoholism develop thiamin deficiency because ethanol reduces gastrointestinal absorption of thiamin, thiamin stores in the liver, and thiamin phosphorylation [3,19].
Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
Effect: up to 80% deficient in chronic alcoholism
Certainty: Deficiency risk group; the passage says nothing about sleep.
NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
ev-b1sl-13 · Position of an expert body · agency fact sheet · n = —
Bariatric surgery for weight loss is associated with some risks, including severe thiamin deficiency due to malabsorption that can lead to beriberi or Wernicke’s encephalopathy.
Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
Effect: severe deficiency risk after bariatric surgery
Certainty: Risk statement only; the passage gives no dose or prevention advice.
NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section
ev-b1sl-14 · Position of an expert body · agency fact sheet · n = —
In its early stage, thiamin deficiency can cause weight loss and anorexia, confusion, short-term memory loss, and other mental signs and symptoms; muscle weakness; and cardiovascular symptoms (such as an enlarged heart) [7].
Who: General population, NIH Office of Dietary Supplements thiamin fact sheet
Effect: early deficiency: weight loss, anorexia, confusion, short-term memory loss, mental signs; sleep not listed
Certainty: ods_search 'thiamin sleep' returned nothing.
NIH Office of Dietary Supplements, Thiamin fact sheet for health professionals · checked 2026-10-07 · we read the section

How this page was made. Evidence was extracted from primary sources into cards, every number was re-checked against the source, and the text was written from those cards. Bioma Learn has no human medical reviewer at this time, and we say so rather than invent one. Methodology. This is information, not medical advice.