Hypophosphatemia

What is hypophosphatemia?

Hypophosphatemia happens when you have a low level of phosphate in your blood. Phosphate is an essential electrolyte you need for several bodily functions.

Hypophosphatemia can be mild or severe. It can also be acute (sudden) or chronic (long term).

How does phosphate affect my body?

Phosphate is a charged particle that contains the mineral phosphorus. Your body needs phosphorus for several important bodily functions, including:

• Building and repairing your bones and teeth.
• Helping your nerves function.
• Making your muscles contract (tighten).

Approximately 85% of the phosphorus contained in phosphate is found in your bones. The rest is stored in tissues throughout your body. You get phosphorous/phosphate from the foods you eat.

The level of phosphate in your blood affects the level of calcium in your blood. Calcium and phosphate react in opposite ways: As blood calcium levels increase, phosphate levels decrease. This takes place minute by minute.

A hormone called parathyroid hormone (PTH), which your parathyroid glands release, controls the levels of calcium and phosphate in your blood.

How common is hypophosphatemia?

Mild hypophosphatemia is a relatively common finding in laboratory (blood) tests, affecting about 5% of people in the U.S. It’s often an incidental (insignificant) finding and typically doesn’t cause symptoms.

Acute, severe hypophosphatemia is much more common in people with certain conditions, including:

• Alcohol use disorder.
• Diabetes-related ketoacidosis (DKA).
• Sepsis (severe infection).
• Burns.

It affects up to 80% of people with these conditions.

What are the symptoms of hypophosphatemia?

The symptoms of hypophosphatemia depend on how severe it is.

Most people with mild hypophosphatemia don’t have symptoms. But some people may notice subtle muscle weakness.

Symptoms of severe hypophosphatemia include:

• Muscle pain and bone pain.
• Severe muscle weakness.
• Altered mental status, such as experiencing confusion or irritability.
• Respiratory or heart failure.
• Numbness or weak reflexes.
• Seizures.

Severe hypophosphatemia can result in coma and death if it’s not treated. If you’re experiencing symptoms of severe hypophosphatemia, get to the nearest hospital as soon as possible.

Symptoms of chronic hypophosphatemia

Symptoms of mild chronic (long term) hypophosphatemia include:

• Bone pain.
• Bone fractures.
• Weakness.
• Loss of appetite.

Children with chronic hypophosphatemia often have features of rickets, including:

• Short stature (height) for their age.
• Bowing of leg bones.
• Widening of their wrists and ankles due to bone changes.

It’s important to see your healthcare provider if you or your child has these symptoms.

What causes hypophosphatemia?

Hypophosphatemia has several causes based on whether it’s mild or severe and if it’s acute (sudden) or chronic (long term).

Moderate to severe hypophosphatemia occurs in several medical settings, including the following:

• The recovery phase of diabetes-related ketoacidosis (DKA).
• Alcohol use disorder and during alcohol withdrawal.
• Severe burns.
• Refeeding syndrome (potentially fatal shifts in fluids and electrolytes that may happen when you receive food after prolonged starvation).
• Severe respiratory alkalosis (when your blood doesn’t have enough carbon dioxide).

Causes of chronic hypophosphatemia include:

• Increased parathyroid hormone levels, as in hyperparathyroidism.
• Other hormonal imbalances, like Cushing’s syndrome.
• Vitamin D deficiency.
• Malnutrition and conditions that lead to malabsorption (like intestinal issues).
• Electrolyte imbalances, like hypomagnesemia and hypokalemia.
• Receiving IV iron infusions, especially ferric carboxymaltose (FCM), for iron-deficiency anemia. This typically only happens with repeated infusions.
• Long-term diuretic use.
• Frequent or excessive use of over-the-counter phosphate-binding antacids, including aluminum- calcium- and magnesium-containing antacids.
• Theophylline (a bronchodilator medication) intoxication.

People with advanced chronic kidney disease (especially those on dialysis) often take phosphate binders with meals (prescribed by their kidney specialist) to limit the absorption of dietary phosphate. Long-term use of these binders can cause hypophosphatemia.

How is hypophosphatemia diagnosed?

Healthcare providers diagnose hypophosphatemia with a simple blood test that measures phosphate levels. They’ll diagnose you with hypophosphatemia if your blood phosphate concentration is less than 2.5 milligrams per deciliter (mg/dL).

For reference, normal blood phosphate levels are usually 2.5 to 4.5 mg/dL in adults and 4.5 to 6.5 mg/dL in children. But these ranges can vary depending on the laboratory that tests the blood sample.

The cause of hypophosphatemia, especially acute hypophosphatemia, is usually apparent due to your medical history and symptoms.

As hypophosphatemia is often the result of other conditions, your provider will likely order additional tests to find the cause and check your overall health. Additional testing may include:

• Other blood tests, like a kidney function test, calcium blood test and vitamin D blood test.
• Urinalysis.
• Imaging scans.

What is the treatment for hypophosphatemia?

Treatment for hypophosphatemia involves treating the underlying cause and stabilizing blood phosphate levels.

Healthcare providers most often use oral phosphate replacement medication (pills taken by mouth) to treat mild to moderate cases of hypophosphatemia. They may also recommend eating foods high in phosphorus to correct your phosphate levels.

If hypophosphatemia is severe, they provide phosphate replacement through an IV.

How can I prevent hypophosphatemia?

Not all cases of hypophosphatemia are preventable, especially severe and acute cases. But there are steps you can take to prevent mild hypophosphatemia, such as consuming a healthy, balanced diet.

Foods that are high in phosphorus include:

• Meats and other proteins, like eggs, chicken, turkey, pork, seafood, and organ meat like liver.
• Dairy products, like milk, cheese, cottage cheese and yogurt.
• Nuts and seeds, including almonds, cashews, Brazil nuts, pumpkin seeds and sesame seeds.

Always talk to a healthcare provider before making drastic changes to your eating patterns.

If you have a condition that makes it more likely that you’ll develop hypophosphatemia, like hyperparathyroidism, malabsorption issues or vitamin D deficiency, it’s important to see your healthcare provider regularly and follow your treatment plan for that condition. This can help prevent hypophosphatemia.

What is the prognosis for hypophosphatemia?

The prognosis (outlook) for hypophosphatemia depends on whether it’s mild or severe and acute or chronic. Mild cases typically respond well to treatment. Severe acute cases can lead to complications if you don’t get treatment in time.

What are the possible complications of hypophosphatemia?

Without treatment, chronic hypophosphatemia can result in osteomalacia — a condition in which you have soft bones that are prone to fracture (breaks).

It’s important to get to the nearest hospital as soon as possible if you’re experiencing symptoms of severe hypophosphatemia, like unexplained muscle pain and altered mental status.