Low sodium (hyponatremia): causes and treatment
Dr. Joan J. Morales Lappot, MD3 min read · Leer en español
In briefLow sodium in the blood usually is not about eating too little salt. It is almost always about water: too much of it compared with the sodium in your body.
What it is
Hyponatremia means the sodium in your blood is below about 135 mmol/L. Sodium controls how water moves in and out of cells, including brain cells, so the brain is most sensitive to changes.
Common causes
- Water pills (diuretics), especially thiazides
- Some antidepressants and seizure medicines
- SIADH, when the body holds on to too much water
- Heart failure, liver cirrhosis or advanced kidney disease
- Drinking very large amounts of water or beer with little food
- Vomiting, diarrhea or heavy sweating replaced only with plain water
- Low thyroid or adrenal hormones
- You have confusion, severe headache, vomiting or a seizure
- A lab tells you your sodium is very low
Symptoms
Mild, slow-developing hyponatremia may cause no symptoms, or subtle unsteadiness and poor concentration, which raise the risk of falls. More severe or sudden drops can cause headache, nausea, confusion and, rarely, seizures.
Why treatment is gradual
Treatment depends on the cause: stopping a medicine, limiting fluids, treating the underlying illness or, sometimes, specific medicines. Correcting sodium too quickly can injure the brain, so serious cases are treated in the hospital with careful monitoring.