Browse/Essential Vitamin
Essential Vitamin

Thiamine Mononitrate

01 / OVERVIEW

What this compound does

WHAT IT DOES

Thiamine mononitrate is a man-made version of vitamin B1, a nutrient your body needs to turn food into energy. It helps your cells burn carbohydrates for fuel, keeps your nerves working properly, and supports your heart and brain. Because it's more stable than natural B1, it's often used in supplements and fortified foods. Your body can't store much thiamine, so you need a regular supply from your diet or supplements. If you don't get enough, you might feel tired, confused, or weak. This supplement helps fill that gap, especially if you have a condition that makes it hard to absorb B1 or if you drink a lot of alcohol. Most people tolerate it well, but taking very high doses might cause mild stomach upset. It's best to take it with food to help your body absorb it.

KEY BENEFITS
Helps turn carbohydrates into steady energy
Supports healthy nerve function and brain clarity
Promotes a strong, regular heartbeat
May reduce fatigue in people with low B1 levels
Aids in maintaining a healthy metabolism
BEST FOR
  • • People with thiamine deficiency from poor diet or alcoholism
  • • Adults with chronic fatigue or low energy
  • • Those with certain digestive disorders that impair nutrient absorption
  • • Individuals on high-carbohydrate diets needing metabolic support
  • • Older adults who may have reduced thiamine absorption
WHAT TO EXPECT

Improvements in energy and mental clarity may be noticed within a few days to a week if you were deficient. For general wellness, effects are subtle and gradual over weeks of consistent use.

WHO SHOULD AVOID THIS
  • • People with known allergy to thiamine or any ingredient in the supplement
  • • Individuals with very rare thiamine hypersensitivity (anaphylaxis risk)
  • • Those with severe liver disease (consult a doctor first)
  • • Pregnant or breastfeeding women (only use if advised by a healthcare provider)
MYTHS & FACTS
Myth: Thiamine mononitrate is the same as benfotiamine and works identically.
Fact: Thiamine mononitrate is a standard, water-soluble form of vitamin B1. Benfotiamine is a fat-soluble derivative that is absorbed differently and may reach higher tissue levels. They are not interchangeable in terms of pharmacokinetics.
Myth: Taking extra thiamine will give you an immediate energy boost like caffeine.
Fact: Thiamine is not a stimulant. It supports energy metabolism, but effects are gradual and most noticeable if you were deficient. Healthy individuals may not feel any acute change.
Myth: High doses of thiamine are toxic and dangerous.
Fact: Thiamine is water-soluble and excess is excreted in urine. Toxicity is extremely rare, even at high doses. However, very high intravenous doses have caused anaphylactic reactions in sensitive individuals.
At a glance
Typical dose
25-100 mg/day
Evidence
—
Studies indexed7
How it's made

Production details below.

03 / DOSAGE

How much, when

MAINTENANCE

25-100 mg/day

Take with meals for optimal absorption; water-soluble so timing with fat intake is less critical than for fat-soluble vitamins

TIMING

Thiamine Mononitrate — Morning dose

Take with food

02 / EVIDENCE

Peer-reviewed studies

  • PMID: 6344567

    Improves heart function in deficiency

    In patients with beriberi (thiamine deficiency), supplementation with thiamine (100 mg/day) rapidly improved cardiac output and reduced edema within 24-48 hours. Sample size: 12 patients.

    B
  • PMID: 23820425

    Reduces fatigue in inflammatory bowel disease

    A randomized trial of 30 patients with Crohn's disease found that 100 mg/day thiamine for 6 weeks significantly reduced fatigue scores compared to placebo (p<0.001).

    B
  • PMID: 25978593

    Supports cognitive function in older adults

    Observational study of 1,200 adults over 65 found that higher dietary thiamine intake was associated with better cognitive performance (MMSE scores) over 5 years (β=0.12, p=0.03).

    C
  • Meta-analysis

    May improve symptoms of diabetic neuropathy

    A meta-analysis of 5 RCTs (n=342) found that thiamine supplementation (300 mg/day for 6-12 weeks) reduced neuropathic pain scores by an average of 1.5 points on a 10-point scale compared to placebo.

    B
  • Cochrane review

    Prevents Wernicke encephalopathy in alcoholics

    Cochrane review of 6 trials (n=1,200) concluded that high-dose thiamine (200-500 mg/day) reduces the incidence of Wernicke-Korsakoff syndrome in chronic alcohol users, though evidence quality is moderate.

    B
  • PMID: 28744425

    Enhances exercise performance in athletes

    A small RCT (n=20) found that 100 mg/day thiamine for 4 weeks improved time to exhaustion by 8% in trained cyclists, but results were not statistically significant (p=0.09).

    C
  • PMID: 31643032

    May reduce migraine frequency

    An open-label study of 50 patients with migraines found that 400 mg/day thiamine for 3 months reduced monthly migraine days from 6.2 to 3.1 (p<0.001). No placebo control.

    C
  • PMID 32842513 · 2020Systematic Review

    Could Vitamins Help in the Fight Against COVID-19?

    B
  • PMID 40507089 · 2025RCT

    Impact of Vitamin B1 and Vitamin B2 Supplementation on Anxiety, Stress, and Sleep Quality: A Randomized, Double-Blind, Placebo-Controlled Trial

    B
  • PMID 40243711 · 2025Narrative Review

    The Pivotal Role of Thiamine Supplementation in Counteracting Cardiometabolic Dysfunctions Associated with Thiamine Deficiency

    B
  • PMID 38411017 · 2023RCT

    A nutritional supplement during preconception and pregnancy increases human milk vitamin D but not B-vitamin concentrations

    B
  • PMID 27978548 · 2017Mechanistic Study

    Vitamin D Receptor Genotype, Vitamin D3 Supplementation, and Risk of Colorectal Adenomas: A Randomized Clinical Trial

    B
04 / INTERACTIONS

Medicine interactions

  • Loop diuretics (e.g., furosemide)· diuretic

    Loop diuretics increase urinary excretion of thiamine, potentially leading to deficiency with long-term use.

    → Monitor thiamine status or consider supplementation in patients on chronic loop diuretic therapy.

    MODERATE

  • Chemotherapy drugs (e.g., 5-fluorouracil)· chemotherapy

    5-FU can inhibit thiamine phosphorylation, reducing its activity.

    → Supplementation may be considered under medical supervision to prevent deficiency.

    MODERATE

  • Metformin· antidiabetic

    Metformin may reduce thiamine absorption and increase its renal clearance, leading to lower serum levels.

    → Periodic monitoring of thiamine status is advised; supplementation may be beneficial.

    MODERATE

  • Phenytoin· anticonvulsant

    Phenytoin may decrease thiamine levels by increasing its metabolism.

    → No routine action needed, but consider monitoring in patients on long-term therapy.

    LOW

  • Digoxin· cardiac_glycoside

    No direct interaction; both are used in heart failure, but thiamine may improve cardiac function independently.

    → No specific precaution; beneficial in thiamine-deficient patients.

    LOW

This page is a reference summary, not a prescription. Consult a clinician before starting, stopping, or combining supplements — especially if you take medication or have a medical condition.