Last Updated: December 06, 2024
Medically reviewed by NKF Patient Education Team
About high phosphorus (hyperphosphatemia)
High phosphorus (phosphate) levels in the blood, also called “hyperphosphatemia” (high-per-fos-fa-TEE-me-uh), is a medical problem where you have too much phosphorus in your blood.
Your body needs phosphorus. Its main job is to mix with calcium to build strong bones and teeth. It also plays a key role in making the energy you need for breathing and other biological processes inside your body. But too much phosphorus in your blood can be dangerous for your health.
People living with chronic kidney disease (CKD) are at risk of high phosphorus (hyperphosphatemia). As your estimated glomerular filtration rate (eGFR) goes down, your level of risk for high phosphorus goes up.
Signs and Symptoms
Most people with high phosphorus do not have any symptoms. If symptoms are present, they may include:
- Bone and/or joint pain
- Pruritus (itchy skin)
- Rash
- Small calcium deposits (hard lumps) in your skin or soft tissue (fat, muscle, tendons)
The following symptoms may occur in very severe cases:
- Muscle cramps
- Involuntary (happen without choice or control) muscle contractions
Feeling numb or tingling in the mouth (either one side, tongue, or entire mouth)
Even if you do not have symptoms, living with high phosphorus is dangerous for your long-term health.
Causes
The most common cause of high phosphorus is chronic kidney disease (CKD), especially when it progresses to kidney failure. Your kidneys are responsible for removing extra phosphorus from your body. This stops the phosphorus levels from going too high. As CKD progresses, your kidneys slowly lose their ability to filter the blood. This causes phosphorus (and other natural waste products) to build up in your blood – the kidneys are the main way for phosphorus to get out of the body.
The risk of high phosphorus is low for people with early stages of CKD (when the eGFR is more than 30). As your eGFR goes less than 30, your risk of high phosphorus goes up. So, high phosphorus is most common for people living with stage 4 CKD or stage 5 CKD.
Complications
High phosphorus levels cause your blood vessels to harden and be less flexible. This makes it harder for blood to travel throughout your body. This usually does not happen quickly – it is caused by many weeks and months of constantly high phosphorus levels. So, high phosphorus increases your risk of:
- Cardiovascular disease (heart attack or stroke)
- High blood pressure
- Heart failure
- Death
High phosphorus levels can also be dangerous for bone health. When phosphorus levels are high, it causes your body to break down your bones and makes it harder to rebuild. This is also known as mineral and bone disorder (MBD). It can leave your bones very weak and increase your risk of fractures.
Diagnosis
Tests
A simple blood test is used to measure the level of phosphorus (phosphate) in your blood.
A normal blood phosphorus level in adults is between 2.5 and 4.5 milligrams/deciliter (mg/dL). So, high phosphorus is when the level of phosphorus in your blood is higher than 4.5 mg/dL. The normal range is different (higher) for children and adolescents.
There are many other factors that can guide treatment decisions, including whether and how to treat high phosphorus. So, your healthcare professional will likely order other blood tests when checking your phosphorus levels, including calcium, parathyroid hormone (PTH), and eGFR. When looked at together, your healthcare professional will have a better idea of what is happening in your body to provide you with the best guidance for what to do.
Current guidelines recommend “lowering high phosphorus levels towards the normal range”. This means that while all values higher than 4.5 mg/dL are considered high, they may not always need to be treated. Work with your healthcare team to determine the best way to treat your high phosphorus based on your specific situation.
Treatment
Nutrition
Lowering the amount of phosphorus in your diet is an important step for anybody living with high phosphorus. This can be difficult since phosphorus can be found in many foods.
Natural (organic) phosphorus is found in many protein-rich foods such as meat, poultry, fish, nuts, beans and dairy products. The goal is not to remove these foods from your diet. Many of these foods contain protein and other nutrients that are important for your health. Rather, it is important to find a balance that works for you. Choices should also consider your risk level for high phosphorus, other health conditions, culture, budget, and preferences. The food source is also important - phosphorus in animal foods is absorbed more easily than phosphorus found in plant foods.
Inorganic phosphorus is found in fast foods, ready to eat foods, canned and bottled drinks, enhanced meats, and most processed foods. This type of phosphorus is completely absorbed into your blood. Avoiding these sources of phosphorus can really help you manage your phosphorus levels. To find these sources of phosphorus, check the ingredients list on a nutrition facts label for words with PHOS in them (for example: phosphoric acid, tricalcium phosphate, etc.).
Changing how you eat is hard. Working with a kidney dietitian can help you find the best approach that works for your personal situation.
Medications
For many people who are on dialysis, limiting the amount of phosphorus you eat is not enough to manage high phosphorus levels. If this happens, medications can be used to help (in combination with lowering the amount of phosphorus in your food).
Phosphate binders: These medicines help “bind” the phosphorus in your food. This helps stop the phosphorus from getting absorbed into your body. These must be taken every time you eat, including meals and snacks. They are available in many forms, including tablets, capsules, chewable tablets, powders, and liquids. So, talk with your healthcare professional about the options to see which one(s) may best suit you.
Some phosphate binder examples include:
- calcium acetate (Phoslo, Phoslyra, Eliphos, Calphron)
- calcium carbonate (Tums)
- ferric citrate (Auryxia)
- lanthanum carbonate (Fosrenol)
- sevelamer (Renagel or Renvela)
- sucroferric oxyhydroxide (Velphoro)
Most of these options are only approved for use in people who are also receiving dialysis treatments.
Phosphate blocker: This medicine also helps stop phosphorus absorption, but in a slightly different way. Instead of binding directly with phosphorus in your food, it blocks the place in your intestine where phosphorus gets absorbed. It is taken twice daily to provide “round the clock” coverage (unlike binders which must be taken with every meal).
The only available phosphate blocker is tenapanor (Xphozah). It is only approved for use in people who are also receiving dialysis treatments.
For many people, the combination of a phosphate binder and a phosphate blocker may be needed to help manage phosphorus levels, even after limiting the amount of phosphorus in the diet.
Dialysis
Dialysis can help remove some of the phosphorus from the blood, including both hemodialysis and peritoneal dialysis. For most people, dialysis does not remove enough phosphorus to reach the goal range. So, the primary focus of treatment is to limit how much phosphorus enters your blood in the first place.
On the other hand, people who receive hemodialysis treatments at home (either short daily or nocturnal [overnight]) have a lower risk of developing high phosphorus levels because they’re getting dialysis treatments more often. If you are on in-center hemodialysis, ask your healthcare professional if your dialysis settings can be adjusted to help lower your phosphorus.
Preparing for your appointment
Questions to ask
- What was my most recent phosphorus level?
- Keeping track of your phosphorus levels long-term is important, especially since treatment decisions are made based on patterns over time. Having one high result may not warrant treatment but repeat levels higher than the normal range might.
- What is my goal phosphorus level or range?
- Each person is different, and the normal range is not always the recommended goal. Work with your healthcare professional to identify the appropriate goal for you. This will help you understand your lab reports better and know what you are working towards to improve your health.
- How often should my phosphorus levels be checked?
- Recommendations for testing frequency vary based on your stage of CKD, your risk factors for high phosphorus, and your other health conditions. Some people may only need to be checked 1-2 times per year while others need a test every month. Talk with your healthcare team to see what is best for your situation.
- Can you refer me to a kidney dietitian?
- It can be hard to find ways to lower the amount of phosphorus in your diet. It’s also possible to accidentally remove healthy foods while trying to lower your phosphorus levels. Working with a kidney dietitian can help ensure you get the right information, personalized for you.
- [If having side effects or problems taking medicine] Can any of my symptoms be side effects of the medication I take to lower my phosphorus? If so, would it be possible to try something different?
- Many people have intolerable side effects from medications and never tell their healthcare team. Similarly, some people may have problems with the taste or size of a medication. This may cause them to skip doses and/or take the medicine incorrectly. Both approaches can be dangerous. So, talk with your healthcare professional about what you’re experiencing. With so many options available now, there is a high chance of finding a good alternative that works better for you.
