Can high hba1c cause high potassium levels?

Indirectly: If you mean hga1c, that is a test for diabetes. Diabetes is the number 1 cause of renal failure in the United States. Since potassium only leaves the body through the urine and stool, if your kidney function worsens with poorly controlled diabetes resulting in high hga1c, your kidneys may not be able to control the potassium level resulting in high potassium.