What could make my potassium levels go up? i take zanaflex (tizanidine) could that cause it ?

Check with doctor. : Your doctor can help answer your question after a careful review of your medical history and current medication usage including nonprescription medications and supplements. Avoid tight fist clenching when they draw your blood as this can result in a phenomenon known as pseudohyperkalemia. Zanaflex (tizanidine) probably is not responsible.