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.
Electrolytes are substances that have a natural positive or negative electrical charge when dissolved in water. Your blood is over 90% water, and it contains certain electrolytes, including phosphate. Electrolytes help your body regulate chemical reactions, maintain the balance between fluids inside and outside your cells and more.
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.
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. A typical nutritious diet provides 1000 to 2000 milligrams (mg) of phosphate daily. Of this, your intestines absorb about 600 mg to 1200 mg.
Your body needs vitamin D in order to absorb phosphate. Your kidneys help control the levels of phosphate in your blood by filtering out extra phosphate and eliminating it through your urine (pee). Your kidneys can also reabsorb phosphate instead of filtering it out if you have low phosphate levels.
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.
A hormone called parathyroid hormone (PTH), which your parathyroid glands release, controls the levels of calcium and phosphate in your blood. Most people have four pea-sized parathyroid glands located behind their thyroid gland — the butterfly-shaped gland in your neck. Like your thyroid, your parathyroid glands are part of your endocrine system.
What’s the difference between phosphate and phosphorus?
Phosphorus is a mineral found in certain foods that combines with other substances in your body to form phosphate compounds. Phosphorus and phosphate are often used interchangeably when talking about testing, but it’s actually the amount of inorganic phosphate in your blood that’s measured with a blood phosphorus/phosphate test.
Who does hypophosphatemia affect?
Hypophosphatemia can affect anyone. Acute and severe hypophosphatemia is relatively rare and is more common in people who are hospitalized or admitted to intensive care units (ICUs).
How common is hypophosphatemia?
Mild hypophosphatemia is a relatively common laboratory abnormality and is often an incidental (insignificant) finding. In this case, it typically doesn’t cause symptoms and is present in up to 5% of people.
Acute and severe hypophosphatemia is much more prevalent in certain conditions, such as alcohol use disorder, diabetes-related ketoacidosis (DKA) and sepsis, with a frequency of up to 80%.
Symptoms and Causes
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 (are asymptomatic), and it’s an insignificant finding in bloodwork panels. Some people with mild hypophosphatemia may have generalized mild to moderate muscle weakness.
Symptoms of severe hypophosphatemia include:
- Muscle pain and bone pain.
- Muscular weakness.
- An altered mental state, such as experiencing confusion or irritability.
- Numbness or reflexive weakness.
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.
What causes hypophosphatemia?
Hypophosphatemia has several causes based on if it’s mild or severe and if it’s acute (sudden) or chronic (long-term).
Medically significant hypophosphatemia occurs in several medical settings, including the following:
- The recovery phase of diabetes-related ketoacidosis (an acute and life-threatening complication of diabetes, mainly Type 1 diabetes).
- Chronic alcohol use disorder and during alcohol withdrawal.
- Severe burns.
- Refeeding syndrome (a syndrome that results in potentially fatal shifts in fluids and electrolytes that may occur 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, such as in Cushing’s syndrome.
- Vitamin D deficiency.
- Electrolyte disorders, such as hypomagnesemia (low blood magnesium levels) and hypokalemia (low blood potassium levels).
- Long-term diuretic use.
- Theophylline (a bronchodilator medication) intoxication.
People with advanced chronic kidney disease (especially those on dialysis) often take phosphate binders with meals to limit the absorption of dietary phosphate. Long-term use of these binders can cause hypophosphatemia.
Diagnosis and Tests
How is hypophosphatemia diagnosed?
Healthcare providers diagnose hypophosphatemia with a simple blood test that measures phosphate levels. They diagnose someone with hypophosphatemia if their blood phosphate concentration is less than 2.5 milligrams per deciliter (mg/dL).
For reference, normal blood phosphate levels are usually 3 to 4.5 mg/dL in adults and 4 to 7 milligrams mg/dL in children. However, these ranges can vary depending on the laboratory that tested the blood sample.
The cause of hypophosphatemia, especially acute hypophosphatemia, is usually evident due to medical history and symptoms.
Healthcare providers often consider possible hypophosphatemia when people have the following conditions or symptoms:
- Poor nutritional status, such as in cases of anorexia nervosa.
- Symptoms or history of intestinal malabsorption.
- History of antacid use.
- Frequent or recurrent bone pain.
- History of or suspicion for multiple myeloma (a type of blood cancer).
- Certain medication use, including chronic glucocorticoids (a group of steroids), cisplatin (a chemotherapy drug) or pamidronate (medication that treats high blood calcium levels).
- Any hospitalization requiring an intensive care unit setting.
What tests will be done to diagnose hypophosphatemia?
Healthcare providers use a blood test to diagnose hypophosphatemia. Since hypophosphatemia is often the result of other conditions, your provider will likely order additional tests to determine the cause of hypophosphatemia and to check your overall health.
Additional testing may include:
- Other blood tests, such as a kidney function test, calcium blood test and vitamin D blood test.
- Imaging scans.
Management and Treatment
How is hypophosphatemia treated?
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 a diet high in phosphorus to correct your phosphate levels. If hypophosphatemia is severe, they provide phosphate replacement through an IV.
How can I prevent hypophosphatemia?
While not all cases of hypophosphatemia can be prevented, especially severe and acute cases, there are steps you can take to prevent mild hypophosphatemia.
You can often fix mild hypophosphatemia and prevent future episodes by adding more phosphorus to your diet or by taking a phosphate supplement. Foods that are high in phosphorus include:
- Meats and other proteins, such as chicken, turkey, pork, salmon and organ meat like liver.
- Fat-free dairy products, such as cottage cheese and yogurt.
- Nuts and seeds, especially pumpkin and sunflower seeds.
If you have low vitamin D levels, you'll also need to increase your intake of this vitamin.
Always talk to your healthcare provider before making drastic changes to your diet.
Outlook / Prognosis
What is the prognosis (outlook) for hypophosphatemia?
The prognosis (outlook) for hypophosphatemia depends on if it’s mild or severe and if the underlying cause is treated. Mild cases that are treated with dietary phosphate generally have great outcomes.
What are the complications of hypophosphatemia?
If left untreated, chronic hypophosphatemia can result in osteomalacia.
If left untreated, acute hypophosphatemia can result in the following complications:
- Metabolic encephalopathy.
- Heart failure.
It’s important to get to the nearest hospital as soon as possible if you’re experiencing symptoms of severe hypophosphatemia, such as unexplained muscle pain and altered mental states.
When should I see my healthcare provider?
If you have a condition that makes it more likely that you’ll develop hypophosphatemia, such as hyperparathyroidism, alcohol use disorder or vitamin D deficiency, it’s important to see your healthcare provider regularly and to follow your treatment plan for that condition.
If you’re experiencing unexplained muscle weakness, contact your provider. They can run some tests to see if hypophosphatemia is the cause.
When should I go to the emergency room (ER)?
If you’re experiencing symptoms of severe hypophosphatemia, such as muscle and bone pain and altered mental states, get to the nearest emergency room as soon as possible.
A note from Cleveland Clinic
Phosphate is a very important electrolyte in your blood. Mild hypophosphatemia is a somewhat common laboratory finding that usually isn’t a cause for concern. Your healthcare provider may recommend getting more sources of phosphorus in your diet. If you have a condition that raises your risk for severe or chronic hypophosphatemia, such as alcohol use disorder or Cushing’s syndrome, talk to your healthcare provider. Ask how you can prevent hypophosphatemia and the signs to look for. Your provider is available to help.
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