My sodium is low — should I eat more salt?

Usually no. Low sodium (hyponatraemia) is almost always a water-balance problem, not a salt-deficiency problem — eating more salt rarely fixes it and can sometimes make things worse. The first step is finding the cause (medications, illness, water intake patterns, hormonal issues) and addressing that. Adding dietary salt without understanding why sodium is low is not a safe self-treatment.

I take a diuretic and my sodium is low — what should I do?

This is one of the most common medication-related causes of hyponatraemia, particularly with thiazide diuretics (hydrochlorothiazide, chlorthalidone, indapamide) in elderly patients. Do not stop the medication on your own — diuretics are usually treating something important (blood pressure, heart failure). Speak to the doctor; they may adjust the dose, switch to a different diuretic, or change strategy. Sodium often improves within days to weeks of the right adjustment.

Can drinking too much water cause low sodium?

Yes — though this is uncommon in daily life. 'Water intoxication' or exercise-associated hyponatraemia happens when someone drinks very large amounts of plain water during prolonged exercise or in some psychiatric conditions, faster than the kidneys can excrete it. The sodium in blood becomes diluted. Athletes doing long endurance events, outdoor labourers in Indian summers who drink only water without electrolyte replacement, and people with specific medical or psychiatric conditions are at higher risk.

Do I need to fast for a sodium test?

Sodium itself does not change much with recent meals. But since it is usually drawn as part of an electrolyte panel or basic metabolic panel that may include fasting tests, an overnight fast is commonly requested. Stay normally hydrated — do not test after extreme dehydration or right after large fluid intake.

Why is my sodium 'slightly low' on every test but I feel fine?

Persistently mild hyponatraemia (130–134) without symptoms can sometimes be a chronic stable state related to medications, mild SIADH, or other factors. Some elderly adults run slightly low without ill effects. Your doctor will usually look for treatable causes (medication review, thyroid, adrenal, kidney function), but in some people the level remains stable and is monitored rather than aggressively treated. Significant or worsening drops change the approach.

Sodium Test: Normal Range & What It Means

Also seen on reports as: Na, Na+, S. Sodium

What is Sodium?

Sodium is the most abundant electrolyte in blood and one of the body's most tightly controlled chemicals. It works closely with potassium and water to regulate fluid balance, blood pressure, nerve signalling, and muscle function. The kidneys, hormones (ADH, aldosterone), and thirst together keep blood sodium within a narrow range.

Sodium imbalances reflect water balance more than total sodium intake — surprisingly, both low sodium (hyponatraemia) and high sodium (hypernatraemia) usually point to problems with how the body is handling water rather than how much salt is being eaten. This is why doctors investigate the cause of a sodium abnormality alongside hydration, kidney function, and medications, not just dietary salt.

The test is run on a small blood sample drawn from a vein. NABL-accredited Indian labs typically report serum sodium in milliequivalents per litre (mEq/L) or millimoles per litre (mmol/L) — the numbers are the same.

Why doctors order it

Sodium is part of every standard electrolyte panel (often called 'Electrolytes' or 'E+' on Indian lab reports) and is included in basic metabolic panels, kidney function tests, and most pre-operative and admission work-ups. It is the most commonly checked electrolyte after potassium.

Doctors order it specifically when symptoms suggest a sodium or water-balance problem — unexplained confusion, drowsiness, headaches, nausea, muscle cramps, seizures, or unexpected change in alertness. It is also routinely monitored in hospitalised patients, in people on diuretics, on certain psychiatric medications, in heart failure, in chronic kidney disease, in liver cirrhosis, and during pregnancy with vomiting.

Sodium is tracked closely in older adults — hyponatraemia is one of the most common electrolyte problems in elderly Indian patients, often related to medications (diuretics, SSRIs, some antipsychotics, anti-seizure drugs) or to age-related changes in thirst and kidney function. It is also a routine check in patients on tube feeding, in critically ill patients, and after major surgery.

What the result means

Low sodium (hyponatraemia, <135 mEq/L) is the more common abnormality and usually reflects excess water relative to sodium — either too much water (over-hydration, certain medications, SIADH — Syndrome of Inappropriate ADH), or proportionate sodium loss (diuretics, vomiting, diarrhoea, adrenal insufficiency, salt-wasting kidney disease). Mild hyponatraemia (130–134) is often asymptomatic. Significant hyponatraemia (<125) can cause confusion, seizures, and coma; rapid correction can itself be dangerous, so treatment is carefully paced.

High sodium (hypernatraemia, >145 mEq/L) is less common and usually reflects water loss relative to sodium — dehydration from inadequate fluid intake (common in elderly Indian patients, especially during summers and when access to water is limited), uncontrolled diabetes (osmotic diuresis), and rarely diabetes insipidus. Mild elevations often respond to rehydration. Significant hypernatraemia can also cause confusion, weakness, and coma, and needs careful correction.

The most common causes of sodium abnormality in Indian outpatient practice are diuretic-related hyponatraemia (particularly thiazides in elderly patients), heat-related dehydration in summers, hyponatraemia in heart failure or liver cirrhosis, and adrenal or thyroid contributions in less common cases. The kidneys, adrenal hormones, and the body's water-handling machinery all matter.

Reference range

Values in mEq/L (equivalent to mmol/L)

Normal: Roughly 135 – 145 mEq/L
Hyponatraemia (low): Below 135 mEq/L — common, often related to medications or illness
Mild hyponatraemia: 130 – 134 mEq/L — usually asymptomatic; recheck and review medications
Moderate hyponatraemia: 125 – 129 mEq/L — needs evaluation and often treatment
Severe hyponatraemia: Below 125 mEq/L — can cause confusion, seizures; needs medical attention
Hypernatraemia (high): Above 145 mEq/L — usually reflects dehydration; common in elderly and ill patients
Severe hypernatraemia: Above 155 mEq/L — can cause confusion, weakness; needs careful correction

Both low and high sodium are usually problems of water balance rather than dietary salt intake. Rapid correction of severe hyponatraemia can be dangerous (osmotic demyelination); doctors pace treatment carefully. Pregnancy lowers sodium slightly on average — pregnancy-specific interpretation applies.

Common factors that affect the result

Many common medications lower sodium. Thiazide diuretics (used for blood pressure, particularly in elderly Indian patients) are a leading cause of outpatient hyponatraemia. SSRIs (anti-depressants), some antipsychotics, certain anti-seizure medications (carbamazepine, oxcarbazepine), some chemotherapy drugs, and PPIs (proton pump inhibitors) can all contribute. ACE inhibitors and ARBs occasionally cause sodium shifts, though less commonly than they affect potassium.

Hot weather and exercise without electrolyte replacement can both raise sodium (dehydration) and lower it (excessive plain-water intake during prolonged exercise, particularly in runners and outdoor labourers — exercise-associated hyponatraemia). Indian summer heat and outdoor occupational exposure make hyponatraemia and hypernatraemia both relevant in different contexts.

Several conditions affect sodium through their hormonal effects. Heart failure, liver cirrhosis, and nephrotic syndrome cause hyponatraemia through complex fluid-retention mechanisms. Hypothyroidism, adrenal insufficiency, and SIADH (often from cancers, lung disease, or medications) also lower sodium. Diabetes insipidus and uncontrolled diabetes mellitus raise it. Pregnancy lowers sodium slightly through plasma-volume expansion.

When to talk to your doctor

Your sodium is below 135 or above 145 mEq/L and you have symptoms — confusion, drowsiness, headache, weakness, nausea, muscle cramps, or seizures.
Your sodium is below 130 mEq/L even without symptoms — this usually warrants prompt evaluation of medications, hydration, and underlying causes.
You are on a thiazide diuretic (HCTZ, chlorthalidone, indapamide) or SSRI and your sodium has dropped — these are common reversible causes that often need a medication review.
You are elderly, recently unwell, or recently hospitalised and your sodium is abnormal — older adults are particularly susceptible to clinically significant sodium shifts.
You are an athlete or do prolonged outdoor activity in the Indian summer and have had symptoms of exercise-associated hyponatraemia (confusion, severe headache, nausea after long workouts) — this is treatable but needs evaluation.

Related tests

Electrolytes

Potassium

Sodium