Is it possible for triamterene-hctz to cause low potassium?

Yes: HCTZ (hydrochlorothiazide) is a diuretic that can lead to loss of potassium in the urine and subsequently low blood potassium levels. Triamterene can be added to to HCTZ (hydrochlorothiazide) in order to help mitigate this urinary potassium wasting but it isn't always perfect. Sometimes low potassium can still develop on the combination pill which is why periodic electrolyte measurement is necessary for those on diuretics. Hope this helps.