The U.S. Recommended Daily Allowance (RDA) for adults ages 19 years and older is 1.2 milligrams daily for males and 1.1 milligrams daily for females, taken by mouth. The RDA for pregnant or breastfeeding women of any age is 1.4 milligrams daily, taken by mouth. As a dietary supplement in adults, 1-2 milligrams daily is sometimes used. Thiamin is also used to treat thiamin deficiency, metabolic/genetic enzyme deficiency disorders, neuropathy, and Wernicke's encephalopathy (prevention/treatment) under medical supervision.
The Adequate Intake (AI) for infants ages 0-6 months is 0.2 milligram; for infants 7-12 months the AI is 0.3 milligram; for children 1-3 years the U.S. Recommended Daily Allowance (RDA) is 0.5 milligram; for children 4-8 years the RDA is 0.6 milligram; for children ages 9-13 years the RDA is 0.9 milligram; for males ages 14-18 years the RDA is 1.2 milligram; and for females ages 14-18 years the RDA is 1 milligram, taken by mouth. The RDA for pregnant or breastfeeding women of any age is 1.4 milligrams daily, taken by mouth. Thiamin is also used to treat thiamin deficiency/beriberi under medical supervision.
Rare hypersensitivity/allergic reactions have occurred with thiamin supplementation. A small number of life-threatening anaphylactic reactions have been observed with large parenteral (intravenous, intramuscular, subcutaneous) doses of thiamin, generally after multiple doses.
Skin irritation, burning, or itching may rarely occur at injection sites.
Contact dermatitis may occur with occupational exposure and may cause sensitization and lead to dermatitis-type reactions after subsequent oral or injected administrations.
Thiamin is generally considered safe and relatively nontoxic, even at high doses. No clear tolerable upper level (UL) of intake has been established. Dermatitis or more serious hypersensitivity reactions occur rarely.
Large doses may cause drowsiness or muscle relaxation.
Injections of thiamin may cause burning. Reactions can often be avoided by slow administration into larger veins.
U.S. Food and Drug Administration Pregnancy Category: C.