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Sodium levels: why monitor them and what deviations mean
What is sodium and its role in the body?
Sodium is one of the main electrolytes, which plays a key role in maintaining water-salt balance, blood pressure, muscle activity and functioning of the nervous system. The main part of sodium is concentrated in blood plasma and intercellular fluid. Together with potassium, it ensures the conduction of nerve impulses and muscle contraction, in particular the heart.
The body is unable to produce sodium on its own - we obtain it exclusively from food, mainly in the form of table salt (NaCl).
Normal blood sodium level
In a healthy person, the serum sodium level is usually:
135–145 mmol/L
Minor fluctuations are possible depending on the laboratory, age, and health status, but deviations from this range may indicate serious abnormalities.
Causes of low sodium levels (hyponatremia)
Hyponatremia is a condition in which the sodium level in the blood drops below 135 mmol/L.
Main reasons:
Excessive consumption of water or low-sodium fluids
Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
Heart, liver, or kidney failure
Sodium loss through sweat, urine, or gastrointestinal upset (diarrhea, vomiting)
Long-term use of diuretics
Hormonal disorders (e.g., adrenal insufficiency)
Symptoms:
headache
weakness, apathy
cramps
confusion of consciousness
nausea
in severe cases - coma or cerebral edema
Example:
After a marathon, a patient loses a large amount of sodium through sweat and consumes excessive water. Hyponatremia develops with symptoms of disorientation and nausea.
Causes of high sodium levels (hypernatremia)
Hypernatremia is a condition in which sodium levels exceed 145 mmol/L.
Main reasons:
Dehydration due to diarrhea, vomiting, overheating
Insufficient water consumption or drinking restrictions
Diabetes insipidus (fluid loss through urine)
Consuming large amounts of salty foods or sodium solutions
Thirst disorders in the elderly or patients with brain damage
Symptoms:
dry mouth
thirst
anxiety, excitement
tremor, convulsions
muscle weakness
in severe cases - hallucinations, seizures, loss of consciousness
Example:
An elderly patient who lives alone restricts herself to water due to urinary incontinence. On a hot day, she develops hypernatremia with severe headache, dry skin, and disorientation.
Comparison of hyponatremia and hypernatremia
| Indicator | Hyponatremia (<135 mmol/L) | Hypernatremia (>145 mmol/L) |
|---|---|---|
| Sodium content in the blood | Reduced | Increased |
| Common symptoms | Apathy, seizures, confusion | Thirst, dryness, muscle weakness |
| Reasons | Excess water, sodium loss | Dehydration, excess salt |
| Complication | Brain edema, coma | Convulsions, impaired consciousness, death |
Diagnostics and analysis for sodium
To assess sodium levels, the following are used:
Biochemical blood test — determines the concentration of sodium in serum
Urine analysis for sodium — allows you to find out if the body is losing sodium through the kidneys
Estimation of plasma and urine osmolarity — helps differentiate the causes of hypo- or hypernatremia
General clinical picture — important for correct interpretation of results
How to maintain normal sodium levels
Follow water and salt balance in the diet
Do not abuse diuretics or laxatives without medical indications
In the heat or during physical exertion, compensate electrolyte loss
If necessary, use electrolyte solutions, especially with vomiting or diarrhea
Avoid excessive consumption of salty foods, especially with hypertension
Sodium levels are an indicator that has a subtle but serious impact on overall health. A simple biochemical analysis can help detect dangerous disorders in time and prevent complications, especially in people with chronic diseases or an increased risk of dehydration.
