Phosphorus Binders in the Low Phosphorus Diet

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For many people with kidney disease, phosphorus is a difficult dietary guideline to follow. Phosphorus binders are often ordered because of this. 

As a renal dietitian, I have the responsibility of teaching people with kidney disease how to follow a low-phosphorus diet. And with phosphorus binders, I also teach about why, how, and when to take these binders.

So how do you know if you should be taking these meds? Here’s what you need to know when it comes to phosphorus binders.

What is Phosphorus?

Phosphorus is a mineral found in food and our bodies. It is most commonly stored in our teeth and bones. Phosphorus is also part of our cellular membrane. It is even a critical part of our DNA.

Phosphorus is the second-most common mineral found in the body, right after calcium. It pairs with calcium to help form our bones.

Phosphorus Lab Test

Your renal function panel will likely include your phosphorus lab value. This measures the amount of phosphorus in your blood.

The normal range for phosphorus is 2.5 – 4.5 mg/dL. Hyperphosphatemia, however, means levels are above 4.5 mg/dL.

For those on dialysis, phosphorus goals are slightly higher. This is because it can be very difficult to get phosphorus in the normal range. Dialysis blood test results aim for a phosphorus level between 3.5 – 5.5 mg/dL.

High Phosphorus Problems

High phosphorus levels have been shown to advance kidney disease. Other problems that can occur with uncontrolled phosphorus include;

• Calcium deposits to eyes, lungs, blood vessels, and soft tissues
• Itchy skin and rashes
• Heart attack
• Stroke
• Bone breaks and fractures
• Skin lesions and wounds
• Calciphylaxis
• Low calcium levels
• Excess vitamin D levels (vitamin D toxicity)

If levels are consistently above 6.5 mg/dL, there is an increased risk of death.

A health condition known as Bone and Mineral Disorder is associated with high phosphorus levels.

About CKD-Mineral and Bone Disorder (CKD-MBD)

Mineral and bone disorder is one of the most common issues with late stages of kidney disease. You may see it abbreviated as MBD or CKD-MBD.

MBD includes calcium, phosphorus (the minerals), parathyroid hormone levels, and fibroblast growth factor 23 (FGF23). The FGF23 levels increase the risk of heart disease and death. 

When these levels are abnormal, they can cause soft-tissue calcification. 

This means the muscles, blood vessels, tendons, and other “soft” parts of the body are at risk for hardening. 

Think of a licorice candy: at first, it’s soft and flexible. Our blood vessels should be that way. They expand and contract to control blood pressure. 

But, if left out for a period of time it can become stale and harden. That is Mineral and Bone Disorder.

Why is it called Mineral and Bone Disorder? Because the bones get sacrificed. Over time, the calcium and phosphorus get pulled from the bones and go to those soft tissues instead.

You may not feel any symptoms even if your phosphorus is a bit high. However, this is not a reason to ignore it. In fact, this is your opportunity to do something about it before it gets worse. Prescribing phosphorus binders is a treatment to prevent high FGF23 levels.

What are Phosphorus Binders?

Phosphorus binders are prescription medications that can lower your phosphorus levels. They are prescribed by your kidney specialist. Binders “bind” to the phosphorus from the foods in our diet.

Types of Phosphorus Binders

There are many different types of phosphorus binders available. They can be prescription or over the counter. It’s important to follow your doctor’s prescription for whichever binder is decided. Do not take phosphorus binders without first consulting your doctor.

The different types of phosphorus binders include:

• Calcium Carbonate (Tums®)
• Calcium Acetate (PhosLo®)
• Sevelamer hydrochloride (Renagel®)
• Sevelamer carbonate (Renvela®)
• Bixalomer (Kiklin®) 
• Lanthanum Carbonate (Fosrenol®)
• Sucroferric Oxyhydroxide (Velphoro®)

Calcium-Based Binders

Calcium-based binders are some of the most commonly prescribed phosphorus binders. In fact, many insurance companies require a patient to start with calcium acetate before moving to a different binder.

Calcium acetate is a binder that can even be purchased over the counter. Calcium carbonate, also known as Tums ®, is often recommended as a phosphate binder.

Since 2007, KDIGO guidelines have recommended that calcium-based binders are not used. It increases the risk of high calcium levels in the body. This can cause long-term complications including calciphylaxis.

As a renal dietitian, I do not recommend the use of calcium-based phosphorus binders when discussing binder options with nephrologists.

Other Types of Binders Not Recommended

KDIGO also recommends avoiding aluminum-based binders and closely monitoring labs for magnesium-based phosphorus binders. Magnesium-based binders may be an option. However, recommendations also state more research is needed for these binders. Magnesium may be elevated or depleted with CKD. This requires close monitoring.

Upcoming Phosphorus Binders

There are frustrations of timing and size of binders. Therefore, companies are still looking for a better solution to controlling phosphorus for kidney disease. Here are some upcoming binders for 2021.

Tenapanor

The pharmaceutical company Ardelyx announced plans to release a new phosphorus-lowering medication. They hope this will be the first to be taken twice daily rather than with each meal. Nothing is available yet, but they do hope to have this medication available in 2021.

Natural Phosphorus Binders

Some “natural” binders that have been used in the past include niacin and chitin.

Niacin, also known as vitamin B3, has been shown to help reduce phosphorus absorption in the gut. The amide form known as nicotinamide may be prescribed to help with phosphorus. However, research has not been able to provide niacin is enough to control phosphorus without additional phosphorus binders.

The other natural product is chitosan chewing gum. This gum was thought to help bind to the phosphorus in the mouth. However, research has shown that this is an ineffective phosphorus binder.

How do Phosphorus Binders Work?

Phosphorus binders are taken with meals and snacks that include phosphorus. When taken with meals, they can “bind” to the phosphorus that comes from the digested foods.

This binding happens in the gastrointestinal tract. Phosphorus is absorbed in the jejunum, a part of the small intestine.

It’s important to take them with meals and snacks because phosphorus binders work in the gut

Taking binders without food and not been shown to help lower phosphorus levels.

How Many Binders Do I Take?

The prescription provided by your doctor determines the amount of phosphorus binders you will take. It’s extremely important to follow the prescribed amount of binders. Future phosphorus levels may change the dose you are currently taking.

The number of phosphorus binders will also depend on the size and foods in your meal and snack. For example, if you had a snack of an apple, it’s very likely that you would not need to take a binder as fruits and vegetables are not a source of phosphorus.

However, at a meal with a peanut butter and jelly sandwich, you’ll want to take your prescribed binder dose as peanut butter is a source of organic phosphorus.

Eating Out with Phosphorus Binders

It’s extremely important to take your phosphorus binders when going out to eat. Fast food many times has added phosphates. Read more here about fast food and kidney disease. You can also learn how to find inorganic phosphorus.

With each new blood test result, your phosphorus binder dose may change. This is especially the case when you are first starting out with binders as the best type and dose is being evaluated.

Different Binder Needs for Different Meals

Research shows that the number of phosphorus binders needed at different meals can vary. This is why it’s important to discuss the different types of meals and snacks you usually have with your dietitian and nephrologist. This is so you can get the best prescription for your binders.

Side Effects of Phosphorus Binders

The most common side effects of phosphorus binders are;

• Nausea
• Vomiting
• Diarrhea
• Constipation
• Abdominal pain
• Gas
• Change in stool color (especially for iron-based binders)

In many cases, side effects may occur in the beginning (first few weeks) of a newly prescribed binder and may subside. 

It’s important to discuss all experienced side effects with the prescribing physician or your dietitian. This is to assess tolerance of the phosphorus binder.

Cost of Binders

Since binders are one of the most commonly prescribed medications for those on dialysis, it’s not a surprise they cost $1.5 billion dollars annually.

Calcium-based binders are still some of the most cost-effective binders available. Sevelamer is also slightly more affordable as it is covered by most insurance.

The out-of-pocket cost of binders can range from $700 to almost $5,000 per year for just this medication. However, those that did not take phosphate binders spend more per year on hospitalizations compared to those that took their prescribed binders.

Those that took sevelamer binders had a 50% lower risk of hospitalization compared to those that did not take phosphorus binder.

Patient-Assistant Programs

While binders can be expensive, there are financial aid programs available. The National Kidney Foundation has a list of patient assistance programs for phosphorus binders and other medications and treatments.

If you are not on dialysis or do not have access to a renal dietitian or social worker, discuss financial concerns with your prescribing physician. 

If you are on dialysis and struggling with the cost of your medications, speak with your clinic’s social worker or dietitian. You can look at other ways to get copay assistance. Both a great resource for dialysis patients!

Comparison Chart of Phosphorus Binders

Below is a table comparing different phosphorus binders. Use this when discussing phosphorus binders with your prescribing physician.

Type of Binder	Binder Form	Dose per tab/pill	Starting Dose per Meal	Pros	Cons	Side Effects
Calcium Carbonate	Capsule or tablets	500-1250 mg	1 cap/tab	Lower pill burden, potentially cost-effective	Calcium-based: Not recommended	High calcium levels
Calcium Acetate	Capsule, tablets, or liquid	667 mg	2 caps or 10mL	Lower cost, covered by most insurances	Calcium-based: Not recommended	High calcium levels
Magnesium Carbonate	Capsules	63 mg	1-2 caps	No common GI side effects, no calcium	Not a strong binder; high pill burden, risk of high magnesium levels. Not generally recommended.	High magnesium levels
Sevelamer Hydrochloride / Sevelamer Carbonate	Tablets or powder	800 mg or 2,400 mg	1-2 tabs	More affordable, often covered by insurance. Not calcium- or aluminum-based. May reduce total cholesterol and LDL levels.	Not recommended if there is a history of bowel obstruction. Don’t take at the same time as levothyroxine.	Nausea, vomiting, diarrhea, constipation, abdominal pain, lower cholesterol and LDL levels, lower absorption of fat-soluble vitamins and folic acid.
Bixalomer	Capsules	250 mg	1-2 caps	Similar to the effectiveness of sevelamer binders, lower risk of GI side effects	Only available in Japan; high pill burden	Indigestion, constipation, bloating, abdominal pain
Lanthanum Carbonate	Chewable Tablets or Powder	250 – 1000 mg	1 tab	Lower pill burden, max dose 4500 mg/day	More expensive	Nausea, vomiting, diarrhea, constipation, abdominal pain
Ferric Citrate	Tablets	210 mg	1 tab	Lower pill burden, max dose	More expensive, not recommended for those with iron metabolism disorders, excessive iron in the blood	Dark stool, nausea, vomiting, diarrhea, constipation, abdominal pain
Sucroferric Oxyhydroxide	Chewable Tablets	500 mg	1 tab	Lower pill burden, max dose 3000 mg/day	More expensive	Nausea, vomiting, diarrhea, constipation, abdominal pain

Phosphorus Binder Absorption Comparison Chart

See how strong the different binders are when it comes to absorbing phosphorus. 

Binder Name	Estimated Phosphorus Binding Capacity (mg/g)
Calcium carbonate	39
Calcium acetate	45
Sevelamer hydrochloride	21
Sevelamer carbonate	21
Bixalomer	unknown
Lanthanum carbonate	45-500 (varies on reference)
Sucroferric oxyhydroxide	130

This chart compares phosphorus binding between different binders. It is not a method to use in calculating how many binders to take based on dietary phosphorus.

Calculating phosphorus intake to determine binder dosing is not advised nor proven. This is due to different absorption rates of phosphorus in various food groups.

How much dialysis would I need to have to not take binders?

Phosphorus removal differs depending on the type of dialysis.

Hemodialysis treatment lasting 4 hours removes between 600 to 1,200 milligrams of phosphorus. Hemodialysis treatments are generally given three to four times per week. This results in the highest amount of phosphorus removal of 4,800 milligrams.

Approximately 300 to 360 milligrams of phosphorus are removed in continuous ambulatory peritoneal dialysis (CAPD). CAPD removes 2,100 to 2,520 milligrams of phosphorus per week.

A person would need to dialyze 18 to 30 hours per week to prevent the need for a phosphorus binder.

What if My Phosphorus is Still High, even with Phosphorus Binders?

Timing

Taking with food allows phosphorus binders to work best. Even taking it a few minutes before or after can still be effective. However, if you go past 15 minutes after a meal or snack and forget your binder the food (and phosphorus) may already be absorbed.

Dosing

If your phosphorus levels are still high and you are taking your binders as prescribed you may need a dose adjustment. Discuss your current dose with your doctor to see if you need an adjustment in your prescription.

Gut Health

As mentioned above, phosphorus is absorbed in the gut. Constipation may increase the absorption of phosphorus. Therefore, it may increase your phosphorus levels.

Speak with a registered dietitian to assess your fiber and fluid needs to prevent constipation.

If you notice your constipation started when your binder prescription did, speak with your prescribing practitioner.

Dialysis Prescription

You may not be getting enough dialysis to remove phosphorus. Dialysis is not the main way to control phosphorus but it can make a difference. Speak with your dialysis team to make sure you get the right amount of dialysis so you can feel your best.

Diet

Revisit your diet if your phosphorus levels are still high, even with binders.

Organic phosphorus sources like beans and whole grains may need to be limited. However, this is not necessary for many cases. By working with a renal dietitian, you can get a deeper dive into the sources of phosphorus – both organic and inorganic – in your diet.

By following a low phosphorus diet, you can help reduce the amount of phosphorus that is absorbed. Click here to learn more about the low phosphorus diet!

Summary

Binders are generally prescribed when blood phosphorus levels reach over 5.5 mg/dL and cannot come down with the low phosphorus diet alone.

Phosphorus binders can be a very important and helpful part of treatment for kidney disease. While a low phosphorus diet should also be followed to keep phosphorus levels controlled and bones healthy, binders may be needed.

It’s important to take phosphorus binders as prescribed. Also, take within 10-15 minutes of eating a meal or snack. More binders may be needed depending on the size and types of foods in the meal or snack.

Speak with your prescribing physician about if and when you should take binders. Speak with your dietitian about a low phosphorus diet to help keep your phosphorus level controlled.

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