Thiamine
In heart failure, two meta-analyses found no change in heart function, walking distance or mortality. In septic shock, trials found no faster recovery, and two meta-analyses split on mortality but both found less dialysis. Benfotiamine trials in nerve damage disagree. A small Alzheimer's trial found slower decline on one scale. IV thiamine caused reactions in 1.1% of doses, rarely anaphylaxis.
Add to Bio HackChecked 2026-11-09
- Status
- Dietary supplement in the US. Injectable thiamine is a prescription drug.
- Also called
- vitamin B1, thiamin, thiamine hydrochloride, thiamine mononitrate, benfotiamine, allithiamine, sulbutiamine, aneurine
- Taken for
- energy, heart failure, nerve health, diabetic neuropathy, memory, Alzheimer's disease, alcohol-related brain damage, Wernicke's encephalopathy, sepsis, mood
Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on
Shown to help0
No benefit shown in research yet.
What people take it for, and what was found
Mixed results4
Septic shock
Mixed results: one review linked thiamine to fewer hospital deaths in septic shock, another found no difference, and both found less kidney dialysis.
The numbers and sources
- Effect
- Across 6 RCTs in septic shock, thiamine was linked to lower in-hospital mortality (RR 0.80, 95% CI 0.65 to 0.99) and less renal replacement therapy (RR 0.48, 95% CI 0.31 to 0.74) [3]. Across 9 RCTs in sepsis and septic shock, short-term mortality did not differ (OR 0.78, p 0.18). Renal replacement therapy was less common (OR 0.26, p 0.0007), 24-hour lactate was lower (MD -0.35) and organ failure scores improved more (MD 1.15) [4]. At 24 hours, lactate did not differ between 200 mg IV thiamine twice a day and placebo (median 2.5 against 2.6 mmol/L). Time to shock reversal and mortality did not differ. In the 35% who were thiamine deficient at baseline, lactate was lower on thiamine (2.1 against 3.1 mmol/L) [5]. Adding vitamin C and thiamine to hydrocortisone did not change time alive and off vasopressors over 7 days (median paired difference -0.6 hours, 95% CI -8.3 to 7.2) [6].
- Population
- 438 patients in 6 RCTs [3]; 520 patients in 9 RCTs [4]; 88 adults with septic shock at 2 US hospitals [5]; 216 adults in 10 intensive care units in Australia, New Zealand and Brazil [6].
- Sources
- [3], [4], [5], [6]
- Caveats
- The two meta-analyses disagree on mortality, and the second reports odds ratios with p-values only [3][4]. Four of its 9 trials were rated high risk of bias, and its authors call the patient total small [4]. The combination trial was open-label [6]. The thiamine-deficient subgroups were small [5][4].
Wernicke-Korsakoff syndrome in heavy drinkers
One flawed trial found 200 mg a day beat 5 mg on one memory test in heavy drinkers, with no dose pattern. Treatment rests on clinical experience.
The numbers and sources
- Effect
- One usable trial compared five intramuscular doses over 2 days. 200 mg a day did better than 5 mg a day on one memory test (MD -17.9 trials, 95% CI -35.4 to -0.4). Other doses did not differ from 5 mg, and results did not follow a dose response [7].
- Population
- 107 people who abused alcohol, in the one trial with usable data [7].
- Sources
- [7]
- Caveats
- The Cochrane authors found trial evidence insufficient to guide dose, route or duration. The trial had design flaws [7]. Thiamine has been standard treatment for this syndrome for over 50 years, based on case reports and clinical experience [7].
Diabetic nerve damage (benfotiamine)
Small trials found mixed results: one 3-week trial improved nerve scores and pain in diabetes, while two longer trials found no change in nerve function.
The numbers and sources
- Effect
- Sources disagree. Over 3 weeks, 400 mg a day of benfotiamine improved a neuropathy score (P = 0.029) and pain (P = 0.041) against placebo. Vibration sense did not change [8]. Over 24 months, 300 mg a day raised blood thiamine and did not change peripheral nerve function or inflammatory markers [9]. Over 12 months, 300 mg twice a day did not change corneal nerve fiber length, the primary outcome, or nerve conduction, sensory testing, symptom scores or quality of life against placebo [10].
- Population
- 40 inpatients with type 1 or 2 diabetes and neuropathy [8]; 67 people with type 1 diabetes [9]; 57 people with type 2 diabetes and mild to moderate symptomatic neuropathy [10].
- Sources
- [8], [9], [10]
- Caveats
- All three trials were small. The positive trial lasted 3 weeks [8]. The 12-month trial was a single-center phase II study [10].
Alzheimer's disease and memory decline (benfotiamine)
One pilot trial found less worsening on a dementia rating in people with mild Alzheimer's or memory decline, but its main memory measure did not change significantly.
The numbers and sources
- Effect
- Over 12 months, the rise in ADAS-Cog score was 43% smaller on benfotiamine than placebo, which did not reach significance (P = 0.125). Worsening on the Clinical Dementia Rating was 77% lower (P = 0.034) [11].
- Population
- 70 people with amnestic mild cognitive impairment or mild Alzheimer's dementia [11].
- Sources
- [11]
- Caveats
- One phase IIa pilot trial. The primary outcome did not reach significance [11].
Not shown to help1
Heart failure
Not shown to improve heart function, walking distance, hospitalization or survival in people with heart failure.
The numbers and sources
- Effect
- Across 7 trials, thiamine did not change ejection fraction (WMD 1.65%, 95% CI -1.10 to 4.41), 6-minute walk (WMD 16.5 m, 95% CI -36.6 to 69.6), NT-proBNP or NYHA class [1]. Across 6 trials, mortality, hospitalization and breathlessness did not differ. Heart rate was the only outcome that changed (P = 0.04) [2].
- Population
- 274 people with chronic heart failure in 7 trials [1]; 298 people with symptomatic heart failure in 6 trials [2].
- Sources
- [1], [2]
- Caveats
- Trials were small. Thiamine corrected thiamine deficiency where present [1].
Doses studied
The septic shock trials used 200 mg of IV thiamine twice a day [5][6]. The Wernicke-Korsakoff trial compared five intramuscular doses, from 5 mg a day upward and including 200 mg a day [7]. Benfotiamine trials used 300 mg a day for 24 months [9], 300 mg twice a day for 12 months [10] and 400 mg a day for 3 weeks [8]. The IV safety study used a 100 mg bolus [12]. EFSA found no adequate data to set a tolerable upper intake level for thiamine [13].
Risks
Reported risks1
Reactions to IV thiamine
Limited evidence: about 1% of IV doses caused brief reactions, mostly local irritation. One case report describes cardiac arrest from anaphylaxis after an infusion.
The numbers and sources
- Effect
- Of 1,070 IV doses of 100 mg, 12 caused reactions (1.1%). Eleven were brief local irritation and one was generalized itching (0.093%) [12]. A case report describes cardiac arrest from anaphylaxis after a thiamine infusion, in a man resuscitated after 15 minutes [14].
- Population
- 989 consecutive patients in a prospective study [12]; one 44-year-old man [14].
- Sources
- [12], [14]
- Caveats
- Anaphylaxis evidence is case reports. These findings concern injection, not oral thiamine.
Checked, no increase found1
Side effects of oral benfotiamine
Small trials found side effects about as common as on placebo with oral benfotiamine for up to 12 months.
The numbers and sources
- Effect
- In a 3-week trial, no side effects attributable to benfotiamine were seen [8]. In the 12-month Alzheimer's trial, the authors reported no safety concerns [11]. In a 12-month neuropathy trial at 600 mg a day, adverse event rates did not differ from placebo [10].
- Population
- 40 inpatients with diabetes [8]; 70 people with cognitive impairment [11]; 57 people with type 2 diabetes [10].
- Sources
- [8], [11], [10]
- Caveats
- Small, short trials cannot detect rare harms.
Claims tested and not found
- That thiamine improves heart function in heart failure. Two meta-analyses found no change in ejection fraction, walking distance or mortality [1][2].
- That thiamine speeds recovery from septic shock. Time to shock reversal and time alive and off vasopressors did not differ in two trials [5][6].
- That long-term benfotiamine improves nerve function in diabetes. Over 24 months in type 1 diabetes [9] and 12 months in type 2 diabetes [10], nerve function did not differ from placebo.
Sources
- He S, Wang S, Xu T, et al. Role of Thiamine Supplementation in the Treatment of Chronic Heart Failure: An Updated Meta-Analysis of Randomized Controlled Trials. Clinical Cardiology. 2024. https://doi.org/10.1002/clc.24309
- Syed ARS, Syed AA, Akram A, et al. Does thiamine supplementation affect heart failure? A systematic review and meta-analysis of randomized control trials. Heart & Lung. 2023. https://doi.org/10.1016/j.hrtlng.2023.04.011
- Wang G, Liao X, Liao Y, et al. Thiamin supplementation on mitigating kidney injury and mortality in patients with septic shock: A systematic review and meta-analysis of randomized controlled trials. Nutrition in Clinical Practice. 2026. https://doi.org/10.1002/ncp.70073
- Xu X, Bai X, Cao W, et al. Efficacy of thiamine (vitamin B1) in sepsis and septic shock: A meta-analysis of randomized controlled trials. Clinics. 2026. https://doi.org/10.1016/j.clinsp.2026.100901
- Donnino MW, Andersen LW, Chase M, et al. Randomized, Double-Blind, Placebo-Controlled Trial of Thiamine as a Metabolic Resuscitator in Septic Shock. Critical Care Medicine. 2016. https://doi.org/10.1097/CCM.0000000000001572
- Fujii T, Luethi N, Young PJ, et al. Effect of Vitamin C, Hydrocortisone, and Thiamine vs Hydrocortisone Alone on Time Alive and Free of Vasopressor Support Among Patients With Septic Shock. JAMA. 2020. https://doi.org/10.1001/jama.2019.22176
- Day E, Bentham PW, Callaghan R, et al. Thiamine for prevention and treatment of Wernicke-Korsakoff Syndrome in people who abuse alcohol. Cochrane Database of Systematic Reviews. 2013. https://doi.org/10.1002/14651858.CD004033.pub3
- Haupt E, Ledermann H, Köpcke W. Benfotiamine in the treatment of diabetic polyneuropathy: a three-week randomized, controlled pilot study (BEDIP Study). International Journal of Clinical Pharmacology and Therapeutics. 2005. https://doi.org/10.5414/CPP43071
- Fraser DA, Diep LM, Hovden IA, et al. The Effects of Long-Term Oral Benfotiamine Supplementation on Peripheral Nerve Function and Inflammatory Markers in Patients With Type 1 Diabetes. Diabetes Care. 2012. https://doi.org/10.2337/dc11-1895
- Ziegler D, Sipola G, Strom A, et al. Effects of benfotiamine treatment over 12 months on morphometric, neurophysiological and clinical measures in type 2 diabetes patients with symptomatic polyneuropathy: a randomized, placebo-controlled, double-blind clinical trial (BOND study). BMJ Open Diabetes Research & Care. 2026. https://doi.org/10.1136/bmjdrc-2025-005773
- Gibson GE, Luchsinger JA, Cirio R, et al. Benfotiamine and Cognitive Decline in Alzheimer's Disease: Results of a Randomized Placebo-Controlled Phase IIa Clinical Trial. Journal of Alzheimer's Disease. 2020. https://doi.org/10.3233/JAD-200896
- Wrenn KD, Murphy F, Slovis CM. A toxicity study of parenteral thiamine hydrochloride. Annals of Emergency Medicine. 1989. https://doi.org/10.1016/S0196-0644(89)80215-X
- European Food Safety Authority. Overview on Tolerable Upper Intake Levels as derived by the Scientific Committee on Food (SCF) and the EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA). Version 11. 2025. https://www.efsa.europa.eu/sites/default/files/assets/UL_Summary_tables.pdf
- Juel J, Pareek M, Langfrits CS, et al. Anaphylactic shock and cardiac arrest caused by thiamine infusion. BMJ Case Reports. 2013. https://doi.org/10.1136/bcr-2013-009648