Where are sodium and potassium found, and what are their normal values?

　　Under normal circumstances, sodium and potassium are two important electrolytes in the human body, primarily found in intracellular and extracellular fluids. The normal range of sodium in plasma is 135–145 mmol/L, and the normal range of potassium in plasma is 3.5–5.5 mmol/L. A detailed explanation is as follows:

　　Sodium is mainly present in extracellular fluid, including plasma, tissue fluid, and lymph, whereas potassium is primarily located in intracellular fluid, including the fluid inside cells and within bone tissue. Under normal conditions, the levels of sodium and potassium in the body should be maintained within certain ranges to preserve the body's water and electrolyte balance. Normally, the concentration of sodium in plasma ranges from 135–145 mmol/L, and the concentration of potassium in plasma ranges from 3.5–5.5 mmol/L.

　　In addition, the reference ranges may vary slightly depending on different laboratories and testing methods; therefore, the specific normal values should be interpreted according to a physician’s assessment or the laboratory report. If abnormalities in sodium or potassium levels occur, it is important to promptly consult a doctor for further evaluation, diagnosis, and treatment.