Serum/Plasma Sodium Concentration (Hyponatremia/Sodium Level)

Why This Test Matters

Sodium is a key mineral that helps regulate how fluids move in and out of your cells. Too little sodium (hyponatremia) can cause headaches, confusion, or even seizures, while too much (hypernatremia) may lead to dehydration symptoms like extreme thirst or muscle spasms. Your doctor may order this test to diagnose conditions like kidney problems, heart failure, or excessive sweating.

When You Might Need It

You may need this test if you have symptoms like confusion, swelling, rapid heartbeat, or unexplained weight gain. Doctors also check sodium levels before surgeries, during chemotherapy, or if you’re taking certain medications (like diuretics) that affect fluid balance.

Sample Collection and Preparation

A blood sample is drawn from a vein, usually in your arm. The blood is sent to a lab where it’s separated into serum or plasma for testing. Sodium levels are measured using an automated method that detects the mineral’s concentration in your blood.

What to Expect Before the Test

No special preparation is needed, but avoid drinking extra water or salt 24 hours before if your doctor directs you to. If you’re on certain medications (like diuretics), let your doctor know—it may affect results.