Which test is used to measure blood sodium levels?

The test used to measure blood sodium levels is the Sodium (Na) test. Sodium is an essential electrolyte that plays a critical role in maintaining fluid balance, nerve function, and muscle contractions in the body. Testing for sodium levels is important for assessing hydration status, kidney function, and determining the cause of various conditions such as hypertension, edema, or electrolyte imbalances.

In the context of the other options, an Iron Panel assesses iron levels and is used to diagnose conditions like iron deficiency anemia. The Potassium (K) test measures potassium levels, another key electrolyte, but does not provide information about sodium levels specifically. Lactate Dehydrogenase is an enzyme that is often measured in the context of tissue damage and does not relate directly to sodium levels. Consequently, the Sodium (Na) test is the most relevant and precise choice for evaluating blood sodium levels.