Written by:

Overview

What Is Hypernatraemia?

Hypernatraemia is an abnormally high level of sodium in the blood. It usually happens when the body has too little water compared with the amount of sodium, rather than because a person has simply eaten too much salt. It is more common in babies, older adults, and people who cannot access water or communicate that they are thirsty. Prompt medical assessment is important because severe hypernatraemia can affect the brain and other organs.

Symptoms

Symptoms of Hypernatraemia

Symptoms of hypernatraemia can develop gradually or appear quickly, depending on how fast the sodium level rises and how much water has been lost. They may be harder to recognise in infants, older adults, or people with impaired communication, so carers may need to look for changes in behaviour, urination, and alertness.

  • Intense thirst (polydipsia).
  • Dry mouth and dry, sticky tissues.
  • Reduced urination (oliguria).
  • Weakness or marked tiredness.
  • Irritability or restlessness.
  • Confusion or changes in alertness.
  • Muscle twitching (fasciculations).
  • Seizures.
  • Loss of consciousness.

Causes

Causes of Hypernatraemia

Hypernatraemia occurs when the body has too little water compared with the amount of sodium in the blood. The most common problem is water loss or inadequate drinking, not simply eating salty food. In some cases, receiving too much sodium through medicines, feeding products, or medical treatment can also contribute.

  • Vomiting can remove water and salts and make it difficult to replace lost fluids.
  • Diarrhoea can cause substantial water loss, especially in infants and older adults.
  • Fever and heavy sweating increase water loss through the skin and breathing.
  • Burns can cause large fluid losses through damaged skin.
  • Excessive urination can remove more water than the person replaces.
  • Diabetes insipidus can prevent the kidneys from concentrating urine properly.
  • Limited access to water or dependence on others for drinks can lead to inadequate intake.
  • Reduced thirst or impaired communication can stop a person from recognising or reporting the need for water.
  • Excessive sodium administration through medicines, intravenous fluids, or concentrated feeds can raise blood sodium.

Risk Factors

Risk Factors for Hypernatraemia

Manageable factors

Vomiting, diarrhoea, fever, uncontrolled diabetes, diuretic use, and inadequate fluid intake may sometimes be reduced or managed with timely medical advice and a suitable fluid plan.

Vulnerability factors

Infancy, older age, dementia, reduced mobility, dependence on carers, kidney disease, and diabetes insipidus can make it harder to maintain water balance or respond to fluid loss.

  • Ongoing diarrhoea or vomiting increases water loss.
  • Fever can increase fluid needs and dehydration risk.
  • Kidney disease may reduce the body’s ability to control water and sodium balance.
  • Diabetes insipidus can cause excessive dilute urination.
  • Uncontrolled diabetes can increase urination and fluid loss.
  • Diuretic medicines can increase urine production and may contribute to dehydration.
  • Tube feeding may increase risk if the prescribed free-water intake is not adequate.
  • Dependence on carers can make access to regular drinks more difficult.
  • Dementia may reduce recognition of thirst or the ability to request water.
  • Reduced mobility may prevent a person from getting drinks independently.
  • Infants depend on adults to provide appropriate fluids.
  • Older adults may have a weaker thirst response or several conditions that increase fluid loss.

Complications

Complications of Hypernatraemia

Severe or rapidly developing hypernatraemia can cause severe dehydration, low blood circulation, and brain dysfunction. Brain-cell shrinkage may lead to seizures, coma, bleeding, or other brain damage, and severe untreated illness can cause shock and death. Sodium must also be corrected carefully: lowering it too quickly can cause brain swelling and further neurological injury.

Diagnosis

How Hypernatraemia Is Diagnosed

A blood test measures sodium and other electrolytes and confirms hypernatraemia. The clinician also reviews symptoms, fluid intake and losses, medicines, and medical history, while checking blood pressure, pulse, weight, and signs of dehydration. These details help show how serious the fluid imbalance is and what may have caused it.

Tests that may identify the cause

Urine sodium and urine osmolality or concentration can show how the kidneys are handling water. Kidney-function tests and glucose testing may identify kidney-related water loss or diabetes, while selected hormone and water-balance tests may help investigate diabetes insipidus or another trigger. Further tests depend on the symptoms and medical history.

Treatment & Management

Treatment and Management of Hypernatraemia

Treatment depends on how high the sodium level is, how quickly it developed, the person’s symptoms and fluid status, and the underlying cause. Severe or symptomatic hypernatraemia may require hospital care, particularly when the person cannot drink safely or has unstable vital signs. The aim is to restore water balance while lowering sodium gradually and safely.

Restore fluid balance safely

Clinicians may give oral or enteral water when this is safe and practical. If the person cannot drink or is medically unstable, carefully selected intravenous fluids may be used. Blood sodium is checked repeatedly so the rate of correction can be adjusted and complications avoided.

Treat the underlying cause and monitor recovery

Treatment may include controlling vomiting or diarrhoea, reviewing diuretics and other medicines, and treating diabetes or an infection. Condition-specific treatment, such as desmopressin for some cases of diabetes insipidus, may be needed. Recovery is monitored with checks of sodium, urine output, kidney function, and fluid intake.

Prevention

Can Hypernatraemia Be Prevented?

Prevention focuses on maintaining appropriate fluid intake and responding early to vomiting, diarrhoea, fever, or heavy sweating. Conditions that cause excessive urination should be managed with clinical support. Extra attention is needed for people who cannot obtain drinks or recognise and communicate thirst.

  • Offer regular, appropriate fluids to infants and dependent adults.
  • Arrange help with drinks and monitoring for people with dementia or limited mobility.
  • Follow clinician guidance about fluids during vomiting, diarrhoea, fever, or other illnesses.
  • Ask a clinician to review medicines if dehydration or excessive urination develops.
  • Avoid using concentrated salt or electrolyte products without medical advice.
  • Seek advice about fluid plans for tube feeding or conditions that cause excessive urination.

Outlook and Prognosis

Outlook and Prognosis

Mild hypernatraemia or hypernatraemia treated promptly often improves when fluid balance is restored safely and the underlying cause is addressed. Severe or prolonged hypernatraemia can cause lasting neurological injury or death, especially if treatment is delayed. The outlook depends on the sodium level, how quickly it developed, the person’s overall health, and whether the underlying illness can be controlled.

When Should You See a Doctor

When Should You See a Doctor?

Get urgent medical help

Do not wait for severe symptoms

Seek emergency help for confusion, severe drowsiness, seizures, fainting, loss of consciousness, inability to drink, or signs of severe dehydration. Vulnerable people with ongoing vomiting, diarrhoea, fever, or markedly reduced urination need urgent assessment.

Contact a clinician promptly for persistent thirst, weakness, reduced urination, or a condition or medicine that increases fluid loss. Do not try to correct possible hypernatraemia rapidly at home with large amounts of water or salt products, because the safest treatment depends on the cause and must be monitored.