A sodium imbalance happens when the level of sodium in your blood falls too low or rises too high. Sodium is one of the most important minerals in your body, and even small changes in its level can affect how your brain, muscles, and heart work. This article explains what causes sodium imbalances, what symptoms they cause, and when you should reach out to your family doctor or visit a walk-in clinic.

What Is Sodium and Why Does It Matter?

Sodium is an electrolyte — a mineral that carries an electrical charge in your body’s fluids. Your body needs the right balance of sodium to function properly. Normal blood sodium levels fall between 135 and 145 mEq/L.

When sodium drops below 135 mEq/L, the condition is called hyponatremia (low sodium). When it rises above 145 mEq/L, it is called hypernatremia (high sodium). Both conditions are types of sodium imbalance that require medical attention.

According to Mayo Clinic’s overview of hyponatremia, this condition is one of the most common electrolyte disorders seen in hospitals and clinics.

How Sodium Imbalance Affects Your Body

Sodium does far more than just add flavour to food. It plays a key role in keeping your body’s internal environment stable — a process called homeostasis. Your body constantly works to keep sodium levels within a narrow, healthy range.

Here are some of the important jobs sodium does in your body:

  • Helps control blood pressure and blood volume

  • Keeps the fluid balance between the inside and outside of your cells

  • Supports nerve impulse conduction and muscle contraction

  • Helps maintain the normal pH (acid-base balance) of your blood

  • Supports the transport of nutrients across cell membranes

Your kidneys play a central role in managing sodium levels. They either hold onto sodium or flush out the excess, depending on what your body needs. Hormones like aldosterone, angiotensin II, and atrial natriuretic peptide help direct this process. However, certain medical conditions can overwhelm these systems, leading to a sodium imbalance.

Causes of Low Sodium (Hyponatremia)

Hyponatremia can develop for several reasons. In many cases, the body is holding onto too much water, which dilutes the sodium in your blood. In other cases, too much sodium is lost through urine, sweat, or other means.

Common Causes of Low Sodium

Several medical conditions increase the risk of developing low sodium. These include:

  • Heart failure — the heart pumps less efficiently, causing fluid to build up

  • Chronic kidney disease — the kidneys cannot regulate sodium and water properly

  • SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion) — the body retains too much water

  • Drinking too much water — this dilutes sodium levels, a condition sometimes called dilutional hyponatremia

  • Certain medications — including thiazide diuretics (water pills), some pain relievers, and some antidepressants

Older adults are especially vulnerable to hyponatremia. Their kidneys may not function as efficiently, and they may take multiple medications that affect sodium levels. If you or a family member takes diuretics, it is worth asking your family doctor about monitoring your electrolyte levels regularly.

Causes of High Sodium (Hypernatremia)

Hypernatremia most often results from not drinking enough water. When the body loses water without replacing it, sodium becomes too concentrated in the blood.

Common Causes of High Sodium

The following situations can raise sodium levels dangerously high:

  • Not drinking enough fluids — particularly in older adults, infants, or people who are unconscious

  • Fever and sweating — the body loses water faster than sodium

  • Uncontrolled diabetes — excessive urination (polyuria) leads to water loss

  • Use of osmotic diuretics — certain medications cause the kidneys to release large amounts of water

  • Hypothalamic damage — the hypothalamus controls the thirst reflex; if it is injured, the body may not signal thirst properly

  • Mechanical ventilation or sedation — patients who are sedated or on breathing machines cannot drink fluids on their own

Infants and elderly Canadians are at the highest risk of hypernatremia. Babies cannot ask for water, and older adults may have a reduced sense of thirst. Caregivers should be especially attentive to fluid intake in these groups. For more context, Healthline’s guide to hypernatremia outlines how quickly this condition can become serious.

Symptoms of Sodium Imbalance

The symptoms of a sodium imbalance depend on which direction sodium has shifted — too low or too high — and how quickly the change occurred. A sudden change is usually more dangerous than a gradual one.

Symptoms of Low Sodium (Hyponatremia)

When sodium drops below 125 mEq/L, the brain is most affected. Brain cells begin to swell as fluid moves into them, increasing pressure inside the skull. This can become life-threatening without prompt treatment.

Symptoms progress in stages as sodium continues to fall:

  • Mild drop: headache, fatigue, and apathy

  • Moderate drop: agitation, confusion, nausea, vomiting, and psychotic-like behaviour

  • Severe drop (below 115 mEq/L): stupor, coma, and permanent neurological damage

A rapid drop in sodium levels produces more dramatic and dangerous symptoms. In contrast, sodium that falls slowly over days or weeks may cause milder symptoms that are easy to overlook.

Symptoms of High Sodium (Hypernatremia)

High sodium causes a different set of symptoms. The body’s cells lose water as sodium draws fluid out of them. This affects the brain and nervous system most severely.

Common symptoms of hypernatremia include:

  • Intense thirst (though this may be absent in older adults or those with brain injuries)

  • Muscle weakness and increased muscle tone

  • Altered mental status — confusion or disorientation

  • Focal neurological deficits (such as weakness on one side of the body)

  • Low blood pressure when standing (orthostatic hypotension)

  • Rapid heart rate (tachycardia)

  • Fever or low-grade fever

  • Swelling in the limbs or lungs (edema)

  • Seizures or coma in severe cases

Neurological complications from hypernatremia can be long-lasting, even after sodium levels return to normal. Therefore, early recognition of these symptoms is critical.

Diagnosing a Sodium Imbalance

Doctors diagnose a sodium imbalance through blood and urine tests. The key measurements include:

  • Plasma sodium level — the main test to confirm hypo- or hypernatremia

  • Plasma osmolality — measures how concentrated the blood is overall

  • Urine osmolality and urine sodium — helps identify why the imbalance is happening

These tests help your doctor understand not just that a sodium imbalance exists, but also what is causing it. Treatment depends heavily on the underlying cause. The World Health Organization’s guidance on healthy diet and minerals reinforces the importance of balanced electrolyte intake for overall health.

In Canada, your provincial health plan covers blood work ordered by a licensed physician. If you are concerned about your sodium levels, your family doctor can order these tests as part of a routine check-up or follow-up.

When to See a Doctor

A sodium imbalance can develop quietly, especially if it comes on slowly. However, some symptoms need urgent attention. Call 911 or go to the nearest emergency room if you or someone you know experiences sudden confusion, seizures, loss of consciousness, or severe vomiting that prevents drinking fluids.

For less urgent concerns, book an appointment with your family doctor. If you do not have a family doctor, a walk-in clinic can order basic blood work and check your electrolyte levels. This is especially important if you:

  • Are taking diuretics (water pills) or antidepressants

  • Have heart failure, kidney disease, or diabetes

  • Are caring for an elderly person or infant who is not drinking enough fluids

  • Have recently had a fever with heavy sweating and little fluid intake

  • Feel persistently tired, confused, or “off” without an obvious reason

Always speak with a qualified healthcare provider before making changes to your diet, fluid intake, or medications. This article is for general information only and does not replace professional medical advice.

Frequently Asked Questions About Sodium Imbalance

What are the first signs of a sodium imbalance?

The first signs of a sodium imbalance often include headache, fatigue, and mild confusion. In low sodium cases, nausea and a general feeling of weakness are common early symptoms. High sodium often causes intense thirst and muscle weakness as early warning signs.

Can drinking too much water cause a sodium imbalance?

Yes, drinking excessive amounts of water in a short period can dilute the sodium in your blood, causing a condition called dilutional hyponatremia. This is sometimes seen in endurance athletes who drink too much plain water during long races. It is important to replace fluids with electrolyte-containing drinks during prolonged exercise.

Who is most at risk of a sodium imbalance in Canada?

Older adults, infants, and people with chronic conditions like heart failure or kidney disease are most at risk of a sodium imbalance. Canadians taking diuretic medications or certain antidepressants should also have their electrolyte levels monitored regularly. Your family doctor can advise on how often to get blood work done.

How is a sodium imbalance treated?

Treatment for a sodium imbalance depends on the cause and severity. Low sodium may be treated by restricting fluid intake, adjusting medications, or, in severe cases, receiving a controlled saline solution in hospital. High sodium is usually treated by carefully replacing fluids — the correction must be done slowly to avoid further brain injury.

Is a sodium imbalance covered under provincial health plans in Canada?

Yes, blood tests to diagnose a sodium imbalance are covered under most provincial health insurance plans when ordered by a licensed physician. You can access these tests through your family doctor or a walk-in clinic. If you are admitted to hospital for a severe electrolyte disorder, that care is also covered under provincial health coverage.

Can a sodium imbalance be prevented?

In many cases, a sodium imbalance can be prevented by staying well-hydrated, eating a balanced diet, and managing underlying health conditions carefully. People taking medications that affect sodium levels should have regular check-ups with their family doctor. Caregivers of elderly individuals or infants should monitor fluid intake closely, especially during hot weather or illness.

Key Takeaways

  • A sodium imbalance means your blood sodium is either too low (hyponatremia) or too high (hypernatremia).

  • Normal blood sodium levels range from 135 to 145 mEq/L.

  • Sodium controls fluid balance, nerve function, muscle contraction, and blood pressure.

  • Low sodium is often caused by heart failure, kidney disease, SIADH, or certain medications.

  • High sodium is most commonly caused by not drinking enough fluids, especially in older adults and infants.

  • Symptoms range from headache and confusion to seizures and coma in severe cases.

  • Older adults, infants, and people with chronic illnesses are at the highest risk.

  • Diagnosis is confirmed through blood and urine tests ordered by your doctor.

  • Seek emergency care for sudden confusion, seizures, or loss of consciousness.

  • Always consult your family doctor or walk-in clinic if you are concerned about your electrolyte levels.