Blood sodium reflects the balance between salt and water in the body. The normal range is about 135 to 145 mmol/L. Hyponatraemia, a low level, is the most common electrolyte abnormality in hospital patients and usually means too much water relative to salt. Hypernatraemia, a high level, almost always means a water deficit.
Because sodium governs how water moves in and out of brain cells, the symptoms are mainly neurological. The speed of change matters more than the number itself, and correction has to be carefully paced.
Symptoms
- Headache, nausea and poor concentration
- Unsteadiness and falls, particularly in older people
- Confusion, drowsiness or personality change
- Muscle cramps
- Intense thirst with high sodium
- Seizures or coma in severe, rapid cases
Causes and risk factors
Low sodium is caused by thiazide diuretics, antidepressants, carbamazepine and other drugs; the syndrome of inappropriate antidiuretic hormone (SIADH) from lung disease, brain conditions or cancers; heart failure, cirrhosis and kidney disease; adrenal insufficiency and severe hypothyroidism; and drinking excessive water, including during endurance events. High sodium follows inadequate water intake in frail or dependent people, fever, diarrhoea, uncontrolled diabetes, and diabetes insipidus, in which the kidneys cannot concentrate urine because antidiuretic hormone is lacking or ineffective, for instance with lithium.
How it is diagnosed
- Serum sodium and osmolality: Confirm a true low-sodium state and its severity.
- Urine sodium and osmolality: Distinguish SIADH, fluid depletion and excess water intake.
- Assessment of fluid status: Clinical examination for dehydration or fluid overload.
- Cortisol and thyroid tests: Exclude hormonal causes before labelling SIADH.
- Imaging: Chest and brain imaging when SIADH has no obvious explanation.
- Water deprivation or copeptin testing: Specialist tests for suspected diabetes insipidus.
Treatment options
- Fluid restriction: First step for SIADH and for low sodium with fluid overload.
- Stopping the causative drug: Often enough when a thiazide or antidepressant is responsible.
- Hypertonic saline: Small boluses in hospital for severe symptoms, with sodium checked every few hours and a strict daily limit on the rise.
- Urea, salt tablets or tolvaptan: Options for persistent SIADH under specialist supervision.
- Water replacement: Oral water or dilute intravenous fluids given gradually for high sodium.
- Desmopressin: Replaces antidiuretic hormone in central diabetes insipidus.
When it is urgent
Seizures, severe confusion, drowsiness, repeated vomiting or a severe headache with a known sodium problem need emergency care immediately and locally. Correction too fast or too slow can both harm the brain, so this is hospital treatment.
Travelling to Türkiye for treatment
Sodium disturbances should be stabilised before any flight. A planned visit can be useful for chronic, unexplained low sodium or suspected diabetes insipidus, where endocrine and nephrology testing and imaging can be completed together. Long-term adjustment of fluids and medication needs a doctor near home.
Send your reports, scans and a short history and a Clinic-Y coordinator replies within 24 hours with suitable teams and written, all-inclusive proposals side by side. Reviewing your case is free.
الأسئلة المتكررة
Should I eat more salt if my sodium is low?
Usually not. Most low sodium is a water problem, not a lack of salt, and the usual advice is to drink less, not to eat more salt.
How much water is too much?
Healthy kidneys handle large volumes, but several litres in a short time, particularly during endurance sport or with certain drugs, can lower sodium dangerously. Drink to thirst.
Is mild chronic low sodium harmless?
It is linked to unsteadiness, falls and poorer concentration, so it is worth finding and treating the cause.