t4/t3 together ( known as Armour ) is now routinely used in the treatment of hypothyroidism -- it is the 'standard of care' which means that if your md is knowledgeable he or she will prescribe them together.... this is more effective than t4 alone -- also t4 or t3 or both together should be made by a compounding pharmacy which your md should know about -- the pharmacy if certified will produce a quality product which means you get what is on the bottle