What electrolytes are abnormal in malnutrition?

November 25, 2025 •

4 min read

According to a study on children with severe acute malnutrition (SAM), over 93% showed an electrolyte imbalance upon hospital admission. Understanding what electrolytes are abnormal in malnutrition is critical for preventing severe, often fatal, health complications related to these metabolic disturbances, particularly during refeeding.

Quick Summary

Malnutrition leads to several electrolyte abnormalities, including deficiencies in potassium, magnesium, and phosphate. Reintroducing nutrition can trigger refeeding syndrome, causing dangerous shifts in electrolyte levels. Severe hyponatremia is also common, influenced by low dietary intake, fluid imbalances, and hormonal changes. Correcting these imbalances is crucial for preventing critical organ dysfunction.

Key Points

Hypokalemia is common: Low potassium is a frequent and serious finding in malnutrition, particularly when complicated by diarrhea, and can lead to cardiac and muscular problems.
Hypomagnesemia often accompanies other deficits: Low magnesium is often present with other imbalances like hypokalemia and hypocalcemia, and its correction is necessary for normalizing other electrolytes.
Refeeding syndrome is a major risk: The hallmark of refeeding syndrome is a rapid and dangerous drop in phosphate, potassium, and magnesium as the body shifts from a catabolic to an anabolic state.
Hyponatremia can occur with fluid overload or loss: Low serum sodium can be caused by excessive water retention in edematous malnutrition or from sodium loss and low intake in other types.
Correction requires careful monitoring: Treating malnutrition-related electrolyte abnormalities involves close monitoring and a cautious, gradual approach to refeeding and supplementation to avoid further complications.

The Critical Role of Electrolytes

Electrolytes are electrically charged minerals dissolved in the body's fluids, including sodium, potassium, chloride, magnesium, phosphate, and calcium. They are essential for numerous bodily functions, including maintaining fluid balance, regulating nerve and muscle function, and ensuring proper heart rhythm. During states of malnutrition, the body's stores of these vital minerals become depleted, leading to predictable and dangerous abnormalities. These imbalances can occur due to inadequate intake, excess fluid loss (e.g., from diarrhea or vomiting), or complex metabolic shifts.

Key Electrolyte Abnormalities in Malnutrition

Hypokalemia (Low Potassium)

Potassium is the most abundant intracellular cation and is vital for cell function, nerve impulses, and muscle contractions. Hypokalemia (serum potassium less than 3.5 mEq/L) is a very common electrolyte abnormality in malnourished individuals, especially children with severe acute malnutrition (SAM) and those with chronic diarrhea.

Causes: Inadequate dietary intake, excessive losses from diarrhea and vomiting, and shifts of potassium into cells, particularly during recovery or in the presence of low magnesium.
Symptoms: Mild cases may be asymptomatic, but severe hypokalemia can cause muscle weakness, fatigue, cramping, intestinal paralysis, and life-threatening cardiac arrhythmias.

Hypomagnesemia (Low Magnesium)

Magnesium is another critical intracellular mineral that acts as a cofactor in hundreds of enzymatic reactions, including those involving energy metabolism and protein synthesis. Low magnesium levels (hypomagnesemia) are frequently seen in malnourished patients and often coincide with other electrolyte abnormalities, particularly hypokalemia and hypocalcemia.

Causes: Inadequate dietary intake, malabsorption from gastrointestinal diseases (like chronic diarrhea), alcoholism, and increased urinary excretion.
Symptoms: Symptoms range from nausea, vomiting, and loss of appetite to severe issues like muscle spasms, seizures, tremors, and abnormal heart rhythms.

Hyponatremia (Low Sodium)

Hyponatremia (low serum sodium) is one of the most common electrolyte alterations in medical practice and is frequently associated with malnutrition. While total body sodium is often high in edematous malnutrition (e.g., Kwashiorkor), the serum concentration is low due to excessive water retention. In non-edematous malnutrition (e.g., marasmus), hyponatremia can result from salt loss via diarrhea or low dietary sodium intake.

Causes: Low dietary sodium, increased water retention due to hormonal changes, and sodium loss from gastrointestinal issues.
Symptoms: Neurological symptoms like headache, confusion, nausea, and in severe cases, seizures and coma can occur.

Hypophosphatemia (Low Phosphate)

Phosphate is a crucial component of adenosine triphosphate (ATP), the body's primary energy source. Hypophosphatemia is a hallmark of refeeding syndrome but can also be an underlying issue in malnutrition. During starvation, phosphate stores are depleted, but serum levels may appear normal. When refeeding begins, the cellular demand for phosphate to synthesize ATP for anabolism causes a rapid and severe drop in serum levels.

Causes: Severely depleted body stores from malnutrition, and a sudden intracellular shift upon refeeding.
Symptoms: Weakness, respiratory failure, seizures, arrhythmias, and cardiac dysfunction.

Hypocalcemia (Low Calcium)

Low serum calcium (hypocalcemia) is also frequently observed in cases of severe malnutrition, often in conjunction with hypomagnesemia. Magnesium is required for proper calcium absorption and metabolism, so a deficiency in magnesium can contribute to low calcium levels.

Causes: Inadequate dietary intake, vitamin D deficiency, and hypomagnesemia.
Symptoms: Subtle clinical signs are common, but severe cases can lead to seizures, particularly in children.

The Dangers of Refeeding Syndrome

Refeeding syndrome is a potentially fatal metabolic complication that occurs in severely malnourished individuals after reintroducing nutrients too quickly. The sudden increase in carbohydrate intake leads to an insulin surge, driving glucose, potassium, magnesium, and phosphate rapidly into cells. This sudden intracellular shift can cause profound and dangerous drops in already depleted serum electrolyte levels. The resulting metabolic disturbances can lead to severe organ dysfunction affecting the heart, lungs, and nerves. Careful, slow refeeding with close monitoring and prophylactic electrolyte replacement is essential to prevent this syndrome. For further reading on the preventative measures for refeeding syndrome, resources like the NIH website can provide additional information. Refeeding Syndrome - StatPearls.

Comparative Overview of Electrolyte Abnormalities in Malnutrition


Electrolyte	Associated Condition	Common Causes	Key Clinical Risks
Potassium (Hypokalemia)	Severe Acute Malnutrition (SAM), Refeeding Syndrome	Chronic diarrhea, low intake, metabolic shifts	Arrhythmias, muscle weakness, paralysis
Magnesium (Hypomagnesemia)	SAM, Refeeding Syndrome, Alcoholism	Inadequate intake, malabsorption, renal loss	Arrhythmias, seizures, tremors
Phosphate (Hypophosphatemia)	Refeeding Syndrome	Starvation followed by refeeding, low intake	Respiratory failure, cardiac failure, seizures
Sodium (Hyponatremia)	SAM (edematous/non-edematous), Fluid Loss	Water retention, diarrhea, low dietary intake	Neurological dysfunction, confusion, seizures

Conclusion

Abnormal electrolyte levels are a predictable and significant complication of malnutrition that can lead to life-threatening outcomes. Hypokalemia, hypomagnesemia, hyponatremia, and hypophosphatemia are the most commonly observed imbalances, each with distinct causes and clinical consequences. Recognition and management are crucial, especially during the initiation of nutritional therapy, where the risk of refeeding syndrome is highest. Prompt assessment, careful electrolyte correction, and slow refeeding under medical supervision are essential to prevent morbidity and mortality in these vulnerable patients.

Frequently Asked Questions

Refeeding syndrome is a metabolic and fluid shift complication that can occur when severely malnourished individuals are fed too rapidly. It is characterized by severe hypophosphatemia, hypokalemia, and hypomagnesemia and can cause cardiac, respiratory, and neurological problems.

Potassium deficiency, or hypokalemia, in malnourished patients is primarily caused by inadequate dietary intake and excessive losses, often due to chronic or severe diarrhea and vomiting. There is also a metabolic shift of potassium into cells during the refeeding process.

Low magnesium levels can make it difficult to correct other electrolyte imbalances. Notably, persistent hypokalemia often cannot be corrected without addressing an underlying hypomagnesemia first, as magnesium is required for proper potassium regulation.

While hyponatremia (low sodium) is more common, it's crucial to understand the context. In edematous malnutrition like Kwashiorkor, there's excess total body sodium but low serum concentration due to water retention. High serum sodium (hypernatremia) is less common but can occur with severe dehydration.

As the body transitions from a starvation state to an anabolic state upon refeeding, it requires phosphate for energy synthesis. This creates a sudden, massive demand for phosphate, which moves from the blood into cells, causing dangerous and rapid hypophosphatemia.

Symptoms can include muscle weakness, fatigue, cramping, irregular heartbeats, and confusion. In severe cases, patients may experience seizures, paralysis, or cardiac arrhythmias.

Treatment involves gradual reintroduction of nutrition, close monitoring of electrolytes, and careful, targeted supplementation. In cases of refeeding syndrome, nutritional support may be slowed down to allow for controlled electrolyte replenishment.