Vitamin B1, also referred to as thiamin, is thought to be highly absorbable from the diet. Good sources of B1 include, meat, legumes, and whole grain products. There are three important functions that B1 plays an essential role in: energy transformation, the synthesis of pentoses and NADPH, and membrane and nerve conduction. The majority of the body's thiamin exists in the skeletal muscles although small amounts can be found in the heart, liver, kidney, and brain.
Skeletal muscle relaxants and loop diuretics should not be combined with thiamine due to a disruption in thiamine activity and a possible thiamin deficiency. The combination of horsetail and thiamin should be avoided as well. As with any drug or supplement, consult a health care professional before use.
Thiamin, or vitamin B1 is well tolerated by most people in doses up to 300 mg per day, even though this is a very high dose. Rare cases of dermatitis and hypersensitivity have been reported when taking B1. The common dosage of vitamin B1 is 1-2 mg per day, or 5-30 mg daily if a person is mildly deficient.