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Dosing

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Standardization:

Dietary sources of thiamin: Beef, Brewer's yeast, legumes (beans, lentils), milk, nuts, oats, oranges, pork, rice, seeds, wheat, whole grain cereals, and yeast. In industrialized countries, foods made with white rice or white flour are often fortified with thiamin (because most of the naturally occurring thiamin is lost during the refinement process).

Dosage forms: Thiamin can be administered orally, intramuscularly, or intravenously. Thiamin is available in 5, 10, 25, 50, 100, 250, or 500 milligram tablets; or as 100 or 200 mg/mL parenteral injections. Maximum concentration is reached in 20-120 minutes for oral administration, and in 2 minutes for intravenous administration. Maximum oral absorption is 8-15mg daily. Oral absorption may be increased by dividing doses, but reduced with the administration of food, or in alcoholics and patients with malabsorption or liver cirrhosis. Patients with normal kidney function excrete 80-96% of intravenous doses, while a small amount is excreted from oral doses.

Adults (18 years and older):

U.S. Recommended Daily Allowance (RDA): The RDA for adults ages 19 years and older is 1.2mg daily for males and 1.1mg daily for females, taken by mouth. The RDA for pregnant or breastfeeding women of any age is 1.4mgdaily, taken by mouth. As a dietary supplement in adults, 1-2mg daily is sometimes used.

Wernicke's encephalopathy (prevention/treatment): 100mg of thiamin administered intravenously (up to 1 gram has been used), followed by 50-100mg daily intravenously or intramuscularly until a regular balanced diet is resumed.

Thiamin deficiency: For mild thiamin deficiency in adults, 5-30mgdaily by mouth has been used in a single dose or in 2-3 divided doses, over a 1-month period (single doses generally do not exceed 30mg). For severe deficiency, up to 300mg has been administered. Parenteral (injected) thiamine is recommended for prevention and treatment of Wernicke's encephalopathy in critically ill people or in alcoholic patients experiencing withdrawal, for example between 50-100 mg of intravenous thiamin in single or divided daily doses, over a 3-day period (or until a therapeutic response is seen). Up to 1 gram may be necessary during the first 12 hours.

Metabolic/genetic enzyme deficiency disorders: For thiamin-responsive genetic enzyme deficiency disorders, 10-20mg daily has been recommended, although up to 600-4000mg daily in divided doses has been used for Leigh's disease.

Neuropathy: 10-20mg daily has been used for mild polyneuropathies, and 30-40mg daily has been used for severe/advanced neuropathies, although safety and effectiveness are not clearly established in patients who are not thiamin deficient.

Children (younger than 18 years):

Adequate Intake (AI) / U.S. Recommended Daily Allowance (RDA): For infants ages 0-6 months the AI is 0.2mg; for infants 7-12 months the AI is 0.3mg; for children 1-3 years the RDA is 0.5mg; for children 4-8 years the RDA is 0.6mg; for children ages 9-13 years the RDA is 0.9mg; for males ages 14-18 years the RDA is 1.2mg; for females ages 14-18 years the RDA is 1mg, taken by mouth. The RDA for pregnant or breastfeeding women of any age is 1.4mg daily, taken by mouth.

Thiamin deficiency/beriberi: Oral doses of 10-50mg daily for 2 weeks followed by 5-10mg daily for 4 weeks have been used. Intravenous doses of 10-25mg daily have been used. Treatment should be under strict medical supervision.

Safety

Allergies:

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 (25-100mg), generally after multiple doses administered for 7 days or more.

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.

Side Effects and Warnings:

Thiamin is generally considered safe and relatively nontoxic, even at high doses. No clear tolerable upper level (UL) of intake has been established. Doses up to 200mg daily for long-term periods or single doses of up to 8 grams have been reported as being nontoxic. Dermatitis or more serious hypersensitivity reactions occur rarely.

Large doses, greater than 100mg, may cause drowsiness or muscle relaxation.

Injections of thiamin may cause burning, which typically occurs with rapid injection of 100mg of thiamin hydrochloride. Reactions can often be avoided by slow administration into larger veins.

Pregnancy and Breastfeeding:

The U.S. Recommended Daily Allowance (RDA)for pregnant or breastfeeding women of any age is 1.4mg daily, by mouth. There is insufficient reliable information available about the safety of using larger amounts during pregnancy or breastfeeding.

Tags: Vitamins

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