Key points
Why the body needs B1
Vitamin B1 (thiamine) works mainly as thiamine pyrophosphate (thiamine diphosphate), a helper of the enzymes that process carbohydrates. The recommended intake for adults is 1.2 mg a day for men and 1.1 mg for women; in the US people usually get about 2 mg from food (Institute of Medicine DRI Report 1998. PMID 23193625[1]). Burgerstein’s handbook, on which this series is based, has no separate chapter on B1 (Burgerstein, Handbuch Nährstoffe 2015, p. 2–4).
Who runs short of B1
Wernicke encephalopathy in plain words
It is acute brain damage caused by a lack of B1. It can be prevented and cured, but it often goes unrecognised during life. In people who misuse alcohol it is suspected when two of four signs are present: undernutrition, eye signs, poor coordination, confusion or mild memory problems (Galvin R Eur J Neurol 2010. PMID 20642790[2]).
Benfotiamine: how it differs
Benfotiamine is a fat-soluble precursor of thiamine: in the body it is converted into ordinary thiamine. In healthy volunteers, compared with thiamine hydrochloride tablets, plasma thiamine was on average about 11 times higher, with a wide spread (1147 ± 490%) (Xie F J Clin Pharmacol 2014. PMID 24399744[3]).
Does benfotiamine help nerves in diabetes
What the studies showed
| What was tested | Who took part | Result |
|---|---|---|
| Benfotiamine vs thiamine tablets, 2014 | Healthy volunteers | On average about 11 times more thiamine in plasma, with a wide spread (1147 ± 490%) |
| BEDIP, 400 mg a day for 3 weeks, 2005 | 40 people with diabetic neuropathy | Neuropathy score and pain decreased more than on placebo |
| BENDIP, 300 or 600 mg a day for 6 weeks, 2008 | 165 people, 133 in the analysis | Main measure improved only in the per-protocol analysis; total symptom score as on placebo |
| 300 mg a day for 24 months, 2012 | 67 people with type 1 diabetes, mostly without symptoms of neuropathy | Nerve function as on placebo |
| BOND, 600 mg a day for 12 months, 2026 | 57 people with type 2 diabetes | Corneal nerve fibres and other measures as on placebo |
Long courses showed no significant effect on the nerves: this does not prove that there is no benefit, but there is no confirmation of benefit yet (Ziegler D BMJ Open Diabetes Res Care 2026. PMID 41571333[6]; Fraser DA Diabetes Care 2012. PMID 22446172[7]).
Safety
The US Institute of Medicine did not set a safe upper level for B1: it could not estimate at what dose harm begins — there are not enough data. No harmful effects of excess thiamine from food and supplements have been described, although this does not yet prove that any dose is safe (Institute of Medicine DRI Report 1998. PMID 23193625[1]). European neurologists rate the safety of thiamine as very good (Galvin R Eur J Neurol 2010. PMID 20642790[2]); in 57 people with type 2 diabetes taking 600 mg of benfotiamine a day for a year, there were no more adverse events than on placebo (Ziegler D BMJ Open Diabetes Res Care 2026. PMID 41571333[6]).
Who should be more careful
- With alcohol misuse: confusion, unsteadiness or odd changes in vision are a reason to call an ambulance, not to take tablets at home.
- After bariatric surgery: discuss B1 monitoring with your doctor, especially in the first months and during pregnancy (Karimi Behnagh A Obes Surg 2024. PMID 38095772[8]).
- With heart failure (one possible cause of a B1 shortage is diuretics): discuss B1 with your cardiologist (Jain A J Card Fail 2015. PMID 26497757[9]).
- With diabetes and tingling or numbness in the feet: benfotiamine does not replace treatment by a doctor. A B12 deficiency causes similar symptoms — see the article on B12 deficiency.
- When taking B-complex products: they usually contain B6, and an excess of it harms the nerves — see the article on vitamin B6.
Bottom line
A B1 shortage is more common with alcohol misuse, after bariatric surgery and in heart failure, and in diabetes plasma thiamine levels are often low. Wernicke encephalopathy is an emergency treated with intravenous thiamine. Benfotiamine is absorbed better and in a short trial eased neuropathy symptoms, but over 12–24 months it showed no significant effect on the nerves. You can discuss whether you need B1 at a consultation.
This material is for information only and does not replace a doctor’s consultation. The dose and form of vitamin B1 are chosen by a doctor based on the results of an examination.
References
- Institute of Medicine DRI Report 1998. PMID 23193625
- Galvin R Eur J Neurol 2010. PMID 20642790
- Xie F J Clin Pharmacol 2014. PMID 24399744
- Haupt E Int J Clin Pharmacol Ther 2005. PMID 15726875
- Stracke H Exp Clin Endocrinol Diabetes 2008. PMID 18473286
- Ziegler D BMJ Open Diabetes Res Care 2026. PMID 41571333
- Fraser DA Diabetes Care 2012. PMID 22446172
- Karimi Behnagh A Obes Surg 2024. PMID 38095772
- Jain A J Card Fail 2015. PMID 26497757
- Thornalley PJ Diabetologia 2007. PMID 17676306
Key facts
- The recommended intake of B1 for adults is 1.2 mg a day for men and 1.1 mg for women; a safe upper level has not been set: there are not enough data on harm (Institute of Medicine, DRI Report 1998).
- Wernicke encephalopathy is treated with thiamine 200 mg 3 times a day, preferably intravenously and before any carbohydrates (Galvin R, Eur J Neurol 2010).
- Before bariatric surgery 7% had B1 deficiency, 3 months after it 19% (an imprecise estimate: 0–68%), a year after it 6% (Karimi Behnagh A, Obes Surg 2024).
- In healthy volunteers benfotiamine gave on average about 11 times more thiamine in plasma than thiamine hydrochloride tablets, with a wide spread (1147 ± 490%) (Xie F, J Clin Pharmacol 2014).
- In 57 people with type 2 diabetes taking 600 mg of benfotiamine a day for 12 months, corneal nerve fibres and other neuropathy measures did not differ from placebo (Ziegler D, BMJ Open Diabetes Res Care 2026).
