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No tolerable upper intake level (UL) has been set for thiamin. The National Academies found too little data to set one for thiamin. Health Canada, which uses the same values, adds that this "does not mean that there is no potential for adverse effects resulting from high intakes." That doesn’t make any amount safe for everyone: talk to your doctor about high doses.
Take several supplements? Add them all up in the Supplement Checker: it shows your thiamin total next to the nutrients that do have a limit.
How much Thiamin you need
| Age | Males | Females | Pregnancy | Breastfeeding |
|---|---|---|---|---|
| Birth to 6 months | 0.2 mg* | 0.2 mg* | – | – |
| 7-12 months | 0.3 mg* | 0.3 mg* | – | – |
| 1-3 years | 0.5 mg | 0.5 mg | – | – |
| 4-8 years | 0.6 mg | 0.6 mg | – | – |
| 9-13 years | 0.9 mg | 0.9 mg | – | – |
| 14-18 years | 1.2 mg | 1 mg | 1.4 mg | 1.4 mg |
| 19-30 years | 1.2 mg | 1.1 mg | 1.4 mg | 1.4 mg |
| 31-50 years | 1.2 mg | 1.1 mg | 1.4 mg | 1.4 mg |
| 51-70 years | 1.2 mg | 1.1 mg | – | – |
| 71+ years | 1.2 mg | 1.1 mg | – | – |
* Adequate Intake (AI): the amount set when there isn’t enough evidence for an RDA.
What counts toward the Thiamin limit
No upper limit (UL) has been set for thiamin.
What happens with too much Thiamin
The National Academies set no UL for thiamin because of a lack of suitable data, and the report notes "a lack of studies designed to detect adverse effects of chronic high intakes of some B vitamins". It adds that the missing UL does not mean high intakes are tolerated, and that "extra caution may be warranted in consuming levels above recommended intakes" (DRI for Thiamin, Riboflavin, Niacin, Vitamin B6…, 1998, Summary).
Sources: Health Canada, Dietary Reference Intakes tables (the joint U.S.-Canada values); National Academies, Dietary Reference Intakes for Sodium and Potassium (2019), DRI summary tables; National Academies, Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998). Limits checked November 8, 2026. More from the NIH: Office of Dietary Supplements Thiamin fact sheet.
If you think you or a child took too much of a supplement, call Poison Control at 1-800-222-1222 (U.S., free, 24 hours) or use poison.org. In an emergency, call 911.
General information, not medical advice. Your doctor may recommend a different amount, for example to treat a deficiency. Talk to your doctor or pharmacist before you start, stop or change a supplement, especially if you are pregnant, nursing, take medication or have a medical condition.