Phosphorus (P)

Phosphate is a type of electrolyte. Electrolytes are electrically charged minerals. They help control the amount of fluid and the balance of acids and bases (pH balance) in your body. Your body also needs phosphates for many other important processes, such as building strong bones and teeth (most of the phosphate in your body is found in your bones where it is combined with the mineral calcium), making energy, and helping your nerves and muscles work properly.

The phosphorus in phosphate comes from the foods you eat, including nuts and seeds, dairy products, dried beans, meats, poultry, and eggs. Your body tightly controls the amount of phosphate in your blood mainly through your kidneys (which filter extra phosphate from your blood and get rid of it through urine) and intestines (which control how much phosphorus you absorb from the foods you eat).

The amount of phosphate in your blood is also linked to your levels of calcium (when blood calcium levels increase, phosphate levels decrease, and when calcium levels decrease, phosphate levels increase), vitamin D (which helps your body use phosphate), and parathyroid hormone (PTH), which helps balance phosphate and calcium levels in your blood. Abnormal phosphate levels may be a sign of problems with the systems in your body that control phosphate levels.

The results of your phosphate test may say "phosphorus levels" or "phosphate levels." These terms mean the same thing. The meaning of your test results depends on your symptoms, medical history, and the results of other tests.

A higher than normal phosphate level is called hyperphosphatemia. High levels are linked to many conditions, including late stages of chronic kidney disease and kidney failure, hypoparathyroidism (where parathyroid glands don't make enough PTH), acidosis (too much acid in your blood from a pH imbalance), and the use of laxatives or enemas that contain phosphate. A rapid rise can pull calcium down and lead to muscle cramps or seizures, while long-term high levels can cause calcium deposits in soft tissues.

A lower than normal phosphate level is called hypophosphatemia. Mildly low levels (about 1.5 to 2.4 mg/dL) often don't cause symptoms. Levels below 1.5 mg/dL can lead to muscle weakness and other problems, and levels below 1.0 mg/dL can be life-threatening. Many conditions that cause low levels may need treatment, including hyperparathyroidism, vitamin D deficiency (which can lead to osteomalacia or rickets in children), being a premature baby, certain rare genetic disorders, severe malnutrition, alcohol use disorder, problems absorbing nutrients, and long-term use of certain medicines such as antacids that contain aluminum hydroxide or calcium carbonate, and certain prescription diuretics.

If your phosphate levels are not normal, it doesn't always mean you have a medical condition that needs treatment. Also, children often have higher phosphate levels because their bones are still growing.