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Hypophosphatemia (Low Level of Phosphate in the Blood)

By James L. Lewis, III, MD

In hypophosphatemia, the level of phosphate in blood is too low.

The phosphate level in blood may become low over time, resulting in chronic hypophosphatemia. Chronic hypophosphatemia usually develops because too much phosphate is excreted (see Overview of Phosphate). Causes include the following:

  • Hyperparathyroidism

  • Chronic diarrhea

  • Use of diuretics for a long time

  • Use of large amounts of aluminum-containing antacids for a long time

  • Use of large amounts of theophylline (used to treat asthma)

The phosphate level in blood can suddenly fall dangerously low in people recovering from the following conditions because the body uses large amounts of phosphate during recovery:

  • Severe undernutrition (including starvation)

  • Diabetic ketoacidosis

  • Severe alcoholism

  • Severe burns

This sudden drop in phosphate level may result in an irregular heart rhythm and even death.

Did You Know...

  • Some people who survived concentration camps died because their already low phosphate level suddenly fell when they began eating a normal diet, a phenomenon called refeeding syndrome.

Symptoms occur only when the phosphate level in blood becomes very low. Muscle weakness develops, followed by stupor, coma, and death. In mild chronic hypophosphatemia, the bones can weaken, resulting in bone pain and fractures. People may become weak and lose their appetite.

Diagnosis and Treatment

The diagnosis is based on blood tests indicating that the phosphate level is low. Doctors do other tests to identify the cause if it is not readily apparent.

Any drugs that can reduce the phosphate level are stopped. If hypophosphatemia is mild and causes no symptoms, drinking low-fat or skim milk, which provides a large amount of phosphate, may help. Or people can take phosphate by mouth, but doing so usually causes diarrhea. If hypophosphatemia is very severe or if phosphate cannot be taken by mouth, phosphate may be given intravenously.

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