Conditions and symptoms
What Is Hyponatremia? Low Blood Sodium
Hyponatremia · say it: hy-po-nuh-TREE-mee-uhAlso written: low sodium, hyponatraemia, low blood sodium
Short answer
Hyponatremia means the level of sodium (salt) in the blood is lower than expected. Some medicines can cause it.
What it means
Hyponatremia means there is too little sodium in the blood compared with water. Sodium helps control the balance of fluid in and around cells, including brain cells. Mild cases may cause no symptoms. Others can cause nausea, headache, tiredness, confusion or unsteadiness. Severe confusion, fits or drowsiness need urgent medical help.
Medicine labels list hyponatremia for several medicines, including some diuretics (water pills), some antidepressants such as SSRIs, and some anti-seizure medicines. Older people are more at risk. The warning is telling your doctor to consider checking a blood sodium level and telling you to report new confusion, headaches or unsteadiness.
Hyponatremia (low sodium) is different from hypernatremia (high sodium). Low blood sodium is usually about water balance, not simply eating too little salt.
Where you may see it
- Medicine leaflets for diuretics and some antidepressants
- Blood test reports, often as 'Sodium (Na)' with an L flag
- Hospital and discharge notes
📄 How it looks on a report
Sodium: (L) Below reference range.
🙅 What it does not mean
- It does not usually mean you should eat more salt; ask your doctor first.
- A slightly low result may not cause symptoms or need urgent action.
- It does not tell you the cause; medicines are one of several possibilities.
🗒️ Questions to ask your doctor
💊 Medicines whose labels mention “Hyponatremia”
Plain-English explanations of each medicine, from its official FDA label.
- Amitriptyline
An antidepressant of the tricyclic type
- Duloxetine
A serotonin and norepinephrine reuptake inhibitor (SNRI) type of antidepressant medicine
- Enalapril
An angiotensin-converting enzyme (ACE) inhibitor
- Escitalopram
a selective serotonin reuptake inhibitor (SSRI), a type of antidepressant
- Fluoxetine
a selective serotonin reuptake inhibitor (SSRI), a type of antidepressant medicine
- Hydrochlorothiazide
A thiazide diuretic, a type of medicine often called a 'water pill'
- Lithium Carbonate
A mood-stabilizing agent, which the label describes as a medicine used to treat bipolar I disorder
- Mirtazapine
An antidepressant medicine. The label describes it as having a tetracyclic chemical structure and belonging to the piperazino-azepine group of compounds.
- Paroxetine
A selective serotonin reuptake inhibitor (SSRI), a type of antidepressant medicine
- Risperidone
an atypical antipsychotic medicine
🔗 Read more from trusted sources
- “Hyponatremia” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “hyponatremia”
Seeing this word on your own report? Get every line of it explained, free.
Explain my report🧩 Related words
🔎 Look up another word
More words: conditions and symptoms
General information about a medical word, not advice about your own results. Ask the clinician who ordered the test what it means for you.