Understanding Hypernatremia: What can cause hypernatremia?

October 20, 2025 •

2 min read

Over 25% of patients in intensive care units develop hypernatremia, a condition of high blood sodium. What can cause hypernatremia is primarily an imbalance in water, often from dehydration, certain medications, and underlying health conditions.

Quick Summary

High blood sodium, or hypernatremia, is most often caused by excessive water loss or insufficient fluid intake. This imbalance can result from dehydration, certain illnesses, and medication side effects.

Key Points

Dehydration is the most common cause: A net deficit of water relative to sodium, often from insufficient fluid intake or excessive fluid loss, is the primary driver of hypernatremia.
Thirst impairment is a key factor: Many at-risk groups, including the elderly and those with altered mental status, have a blunted or impaired thirst mechanism, preventing them from drinking enough water to correct the imbalance.
Medical conditions contribute: Diseases such as uncontrolled diabetes mellitus and diabetes insipidus cause increased water loss through urine, making hypernatremia a potential complication.
Iatrogenic sodium gain is a hospital risk: Excessive intravenous administration of sodium solutions is a known, though less common, cause of hypernatremia, particularly in intensive care settings.
Neurological symptoms indicate severity: Confusion, muscle twitching, seizures, and lethargy are symptoms of severe hypernatremia, resulting from the osmotic shrinkage of brain cells.
At-risk populations require vigilance: Infants, older adults, and critically ill patients are especially vulnerable to hypernatremia due to physical limitations or underlying health issues.

The Core Imbalance: Water Loss vs. Sodium Gain

Hypernatremia is defined as a serum sodium level above 145 milliequivalents per liter (mEq/L), indicating an elevated concentration of sodium in the blood. This condition creates hypertonicity, drawing water out of the body's cells. It is primarily caused by either a net loss of water relative to sodium or, less frequently, excessive sodium gain. The body normally regulates sodium and water balance through thirst and the hormone vasopressin (ADH), which signals the kidneys to retain water. Disruptions to these mechanisms can lead to hypernatremia, posing a risk, especially to vulnerable groups.

Primary Causes of Water Deficit (Dehydration)

Dehydration is the most common cause of hypernatremia. For a detailed breakdown of causes related to dehydration, including impaired thirst, excessive fluid loss from GI issues, increased insensible losses, and kidney disorders like Diabetes Insipidus or those related to uncontrolled Diabetes Mellitus or diuretic use, please refer to {Link: Medscape https://emedicine.medscape.com/article/241094-overview}.

Conditions Leading to Increased Sodium Levels

Increased sodium levels are a less frequent cause but can occur in hospitalized patients. These include iatrogenic sodium administration, accidental ingestion, and hormonal imbalances.

Risk Factors for Developing Hypernatremia

Factors that increase susceptibility include age, certain medical conditions like neurological disorders, chronic kidney disease, uncontrolled diabetes, or diabetes insipidus, hospitalization, critical illness, and some medications like corticosteroids. For further details on risk factors, see {Link: Medscape https://emedicine.medscape.com/article/241094-overview}.

Comparing Water Loss and Sodium Gain Causes


Feature	Water Deficit Hypernatremia	Sodium Gain Hypernatremia
Primary Cause	Loss of free water or hypotonic fluid not adequately replaced.	Gain of hypertonic sodium overwhelming fluid compartments.
Most Common Scenario	Dehydration from insufficient intake, often with excessive losses.	Medically induced administration of excess sodium in hospitals.
Key Patient Group	Elderly, infants, those with impaired thirst or mental status.	Hospitalized and critically ill patients.
Physical Signs	Dehydration and hypovolemia (thirst, dry mouth, low blood pressure).	Hypervolemia (edema, high blood pressure).
Underlying Mechanism	Failure of thirst and vasopressin to maintain water balance.	Excessive sodium intake bypassing normal control.
Fluid Balance	Low total body water relative to sodium.	{Link: Medscape https://emedicine.medscape.com/article/241094-overview}.

Conclusion: Recognizing and Addressing the Root Cause

Hypernatremia can be a serious condition with potential neurological consequences. Most cases result from a net water deficit due to dehydration from inadequate intake or excessive loss. Less often, it's caused by excess sodium gain. Sustained hypernatremia is rare when thirst mechanisms are intact, emphasizing the role of impaired thirst or limited fluid access. Monitoring fluid intake and output is crucial for at-risk individuals like the elderly, infants, and those with chronic conditions. Treatment involves carefully restoring fluid balance based on the cause, avoiding rapid correction to prevent complications like cerebral edema. A medical evaluation is vital to determine the specific cause and guide treatment. For more comprehensive information, refer to {Link: Medscape's Hypernatremia article https://emedicine.medscape.com/article/241094-overview}.

Frequently Asked Questions

The most prominent symptom of hypernatremia is excessive thirst. In more severe cases, individuals may experience neurological symptoms such as fatigue, confusion, muscle twitching or spasms, and, in extreme instances, seizures or a coma.

Diabetes insipidus (DI) disrupts the body's ability to regulate water. In both central and nephrogenic DI, the body produces excessive volumes of dilute urine. If fluid intake does not keep pace with this water loss, the blood's sodium concentration rises, leading to hypernatremia.

Yes, high-protein tube feeding can be a cause of hypernatremia in critically ill patients. The breakdown of protein produces urea, which acts as an osmotic diuretic. This increases urinary output and causes the body to lose free water, concentrating the blood's sodium.

Older adults are more susceptible due to age-related physiological changes. They often have a decreased thirst sensation, reduced kidney function that impairs urinary concentration, and a lower total body water percentage, making them more vulnerable to dehydration.

Treatment focuses on replacing the fluid deficit and addressing the underlying cause. In milder cases, oral fluid replacement may suffice. Severe cases often require a gradual intravenous infusion of dilute fluids, carefully monitored to avoid overly rapid correction.

Certain medications, such as diuretics (especially loop and thiazide diuretics), can cause excessive water excretion. Lithium is another medication that can cause nephrogenic diabetes insipidus, contributing to hypernatremia.

Dehydration is the most common cause of hypernatremia, but they are not the same thing. Hypernatremia specifically refers to an elevated sodium level in the blood, while dehydration is the overall loss of body fluid. While most hypernatremia involves dehydration, not all dehydration leads to hypernatremia.