Why do i get charlie horse in my legs and feet when on hctz (hydrochlorothiazide)?

Possible : Potassium deficiency. Often times a doc gives a patient potassium supplements. Speak to your doc as fluctuations in potassium can have an effect on cardiac function.

Cramping: Also may cause magnesium deficiency. Consider magnesium oxide 400mg twice a day if no improvement with use of potassium. Can get at local pharmacy over the counter or grocery store.