Hypophosphatemia is an abnormally low level of phosphate in the blood. Phosphate is an electrolyte that helps your body with energy production and nerve function. Phospate also helps build strong bones and teeth. You get phosphate from foods like milk, eggs, and meat.
Most of the phosphate in your body is housed in your bones. A much smaller amount is found inside your cells.
There are two types of hypophosphatemia:
- acute hypophosphatemia, which comes on quickly
- chronic hypophosphatemia, which develops over time
Familial hypophosphatemia is a rare form of the disease that’s passed down through families. This form of the disease can also lead to the bone disease rickets, and a softening of the bones called osteomalacia.
Most people with the familial form have X-linked familial hypophosphatemia (XLH). A smaller number have autosomal dominant familial hypophosphatemia (ADHR).
Another rare genetic form of this disease is hereditary hypophosphatemic rickets with hypercalciuria (HHRH). In addition to hypophosphatemia, this condition is characterized by high levels of calcium in the urine (hypercalciuria).
In general, hypophosphatemia is rare. It’s more common in people who are hospitalized or admitted to intensive care units (ICUs). Between 2% and 3% of people admitted to the hospital, and up to 34% of those in ICUs, have this condition.
Many people with mild hypophosphatemia don’t have symptoms. Symptoms may not appear until your phosphate levels drop very low.
When symptoms do occur, they can include:
- muscle weakness
- bone pain
- bone fractures
- appetite loss
- slowed growth and shorter than normal height in children
- tooth decay or late baby teeth (in familial hypophosphatemia)
Because phosphate is found in many foods, it’s rare to have a deficiency — unless you’re malnourished. Certain medical conditions can cause hypophosphatemia by:
- decreasing the amount of phosphate your intestines absorb
- increasing the amount of phosphate your kidneys remove into your urine
- moving phosphate from inside the cells to the area outside the cells
Causes of hypophosphatemia include:
- severe malnutrition, such as from anorexia or starvation
- severe burns
- a diabetes complication called diabetic ketoacidosis
- the kidney disorder, Fanconi syndrome
- an excess of parathyroid hormone (hyperparathyroidism)
- chronic diarrhea
- vitamin D deficiency (in children)
- inherited conditions such as X-linked familial hypophosphatemia (XLH) or hereditary hypophosphatemic rickets with hypercalciuria (HHRH)
Low phosphate levels may also be due to long term or excess use of certain drugs, such as:
- antacids that bind to phosphate
- theophylline, bronchodilators, and other asthma medicines
- mannitol (Osmitrol)
- hormones such as insulin, glucagon, and androgens
- nutrients such as glucose, fructose, glycerol, lactate, and amino acids
- acyclovir (Zovirax)
- acetaminophen (Tylenol)
Familial hypophosphatemia is caused by gene changes (mutations) that are passed down from parents to their children. These gene changes cause the kidneys to remove more phosphate than usual from the blood into the urine.
You’re more likely to get hypophosphatemia if you:
If a medication caused this condition, you’ll need to stop taking the drug.
You can correct mild symptoms, and prevent low phosphate in the future, by adding more phosphate into your diet. Milk and other dairy foods are good sources of phosphate. Or, you can take a phosphate supplement. If your vitamin D levels are low, you’ll also need to increase your intake of this vitamin.
If your hypophosphatemia is severe, you may need to get high doses of phosphate through a vein (IV). People with the familial form will need to take both phosphate and vitamin D supplements to protect their bones. They may also need dental sealants to protect their teeth from decay.
Complications and associated conditions
You need phosphate to maintain healthy bones. A lack of it can lead to bone weakness, fractures, and muscle damage. Very severe hypophosphatemia that isn’t treated can affect your breathing and heart function, and can be life threatening.
Complications of hypophosphatemia include:
- death of muscle tissue (rhabdomyolysis)
- breathing failure
- red blood cell destruction (hemolytic anemia)
- an irregular heart rhythm (arrhythmia)
A mild case of hypophosphatemia usually improves if you add more phosphate to your diet or take a supplement. Severe cases will require IV phosphate treatment.
Your outlook depends on whether the condition that caused your low phosphate levels is treated. Once it has been treated, hypophosphatemia shouldn’t return.