Condition Basics

What is hyponatremia?

Hyponatremia (say "hy-poh-nay-TREE-mee-uh") means that you don't have enough sodium in your blood compared to water. Sodium is both an electrolyte and a mineral. It helps keep the right mix of fluids in your body. Severe hyponatremia can be harmful to the brain and nervous system.

What causes it?

Hyponatremia can be caused by conditions that make you retain water, such as kidney disease, liver cirrhosis, thyroid problems, and heart failure. Some medicines may cause it. It can also happen when you lose water through exercise, vomiting, or diarrhea and then replace it with fluids that don't contain enough sodium.

What are the symptoms?

Hyponatremia may cause nausea, vomiting, headaches, and muscle weakness or cramps. You may not feel hungry. It can cause mood changes and make it hard to think clearly. Severe lack of sodium may lead to seizures or a coma.

How is it diagnosed?

To diagnose hyponatremia, your doctor will examine you and ask about your health. You will also have a blood test to check on the sodium levels in your blood.

How is hyponatremia treated?

Your doctor may treat the medical condition or change the medicine that is causing your low sodium levels. You may get medicine to raise these levels. You may be told to limit the amount of water you drink. You may also add more salt to your diet or drink electrolyte replacement drinks.

How can you prevent it?

Follow your doctor's directions for treating any related problems. If you've had lots of vomiting, diarrhea, or long bouts of exercise (such as running a marathon), consider drinking an electrolyte replacement drink instead of water.


Current as of: March 1, 2023

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD - Internal Medicine
Christine Wendt RD - Registered Dietitian
Colleen O'Connor PhD, RD - Registered Dietitian
Donald Sproule MDCM, CCFP - Family Medicine