An electrolyte panel is a blood test that measures the levels of the body's main electrolytes: sodium, potassium, chloride, and bicarbonate. These minerals help control fluid balance, muscle contractions, and nerve function. The test is often part of a routine blood screening or a comprehensive metabolic panel. It may also be used to diagnose an electrolyte imbalance or to monitor the effectiveness of treatment. There is no special preparation needed for an electrolyte panel. The test is done by drawing blood from a vein in your arm. The results of the test can help your doctor determine if you have an electrolyte imbalance and recommend treatment if needed.