What is vitamin b1 usually prescribed for?

Many things. Thiamine (vitamin b1) is an essential nutrient for many bodily functions & plays a key role in converting food into energy. It can improve energy, help memory, prevent alzheimer's, support cardiac health, improve appetite & digestion, be helpful for diabetics & protect against the harmful effects of alcohol on the brain.See http://www.Vitamins-supplements.Org/vitamin-b1-thiamine.Php for more info.