Thiamin deficiency can be caused from drug/supplement interactions, such as diuretics, phenytoin, or Vitamin B-complex vitamin supplementation. People with renal failure, who are on peritoneal dialysis, need thiamin as well as the elderly and people with a history of alcohol abuse. The symptoms of thiamin deficiency, called Beriberi, maybe peripheral neuropathy, muscle atrophy, and/or cardiovascular issues. The RDA for women is 1.1mg supplementation, however, it is found in our foods. Meat (pork, chicken, and beef), legumes, whole grains and seeds are the best sources of thiamin. Suggest you see your MD if your symptoms do not decrease with supplementation.