Hi nesta, Apple Cider Vinegar (like Braggs) can be safely added to water and food. Try a tablespoon a day. It's naturally high in potassium and commonly fed to dogs and horses. Also, some green leafy veg (raw and mashed up in a liquidiser will add some potassium)

Sodium and potassium ion concentrations are important in membrane transport of charged particles in and out of cells (e.g. proteins, fats). It is critical in creating ion currents in heart cells. Low potassium could lead to heart problems such an irregular beat, or even fibrilation. Frequently in dogs high potassium is seen in such diseases as kidney failure, or diabetes. Low potassium seems to be rare.

If it were my dog I'd go with the Therea K first, and then work with the Vet to see if one could alter the diet with the goal of reducing and later eliminating the prescription supplement. But you should get the potassium levels back to normal as quickly as possible. You should discuss or ask the Vet about possible underlying causes, and how the level is to be monitored initially.

Yes, you should suppplement it, as too low potassium can cause heart arrythmia and eventuall death.

You haven't mentioned what you are feeding, however potassium is present naturally in many foods - so you could also get the necessary potassium through feeding. There are lots of lists on the internet if you google for 'potassium high foods'