Phoslyra (Calcium Acetate) – Oral

What Is Phoslyra?

Phoslyra (calcium acetate) is a prescription medicine used to lower phosphate levels in adults with kidney failure who are on dialysis (treatments that help rid the blood of waste and excess fluids when the kidneys are unable to). Phoslyra belongs to a group of drugs called phosphate binders. It works by binding to phosphate and helping your body excrete it through your feces. Phoslyra is available as an oral solution.

Drug Facts

Generic Name: Calcium acetate

Brand Name(s): Phoslyra

Drug Availability: Prescription

Therapeutic Classification: Phosphate binder

Available Generically: No

Controlled Substance: No

Administration Route: Oral

Active Ingredient: Calcium acetate

Dosage Form(s): Oral solution

What Is Phoslyra Used For?

Phoslyra is used to lower phosphate levels in adults with kidney failure on dialysis. When your kidneys don't work properly, your phosphate levels can become too high. High phosphate levels (called hyperphosphatemia) can weaken your bones and increase your risk of heart attack, stroke, and death. When combined with a low-phosphate diet, Phoslyra helps keep your phosphate levels within a healthy range.

It's unknown how common hyperkalemia is, but around 2% to 3% of the general population likely has high potassium levels. In the hospital setting, the estimate may be up to 10%.

How to Take Phoslyra

Phoslyra is an oral solution and is typically taken three times daily with meals. Use the dosing cup with your prescription to measure your dose correctly. Your healthcare provider will adjust your dose every couple of weeks until your phosphate levels reach a healthy range.


Store your Phoslyra prescription at room temperature (about 77 degrees Fahrenheit).

Keep your medications tightly closed and out of the reach of children and pets, ideally locked in a cabinet or closet.

Avoid pouring unused and expired drugs down the drain or in the toilet. Ask your pharmacist or healthcare provider about the best ways to dispose of this medicine. Visit the Food and Drug Administration (FDA) website to learn where and how to discard all unused and expired drugs. You can also find disposal boxes in your area. Ask your pharmacist or healthcare provider if you have any questions about the best ways to dispose of your medications.

If you travel with Phoslyra, get familiar with your final destination's regulations. In general, be sure to make a copy of your Phoslyra prescription. Keep your medication in its original container from your pharmacy with your name on the label. Ask your pharmacist or healthcare provider if you have any questions about traveling with your medicine.

How Long Does Phoslyra Take to Work?

Phoslyra begins to lower phosphate levels the first day you start taking it. However, it can take several weeks to get your phosphate levels in a healthy range. Your healthcare provider will adjust your Phoslyra dose every couple of weeks until they find the best dose for you.

What Are the Side Effects of Phoslyra?

This is not a complete list of side effects and others may occur. A healthcare provider can advise you on side effects. If you experience other effects, contact your pharmacist or a healthcare provider. You may report side effects to the FDA at or 800-FDA-1088.

Common Side Effects

Phoslyra is generally well-tolerated, but you may experience side effects. Let your healthcare provider know if you develop any side effects that bother you or don't go away. Common side effects include:

  • Diarrhea
  • Nausea
  • Vomiting

Severe Side Effects

Phoslyra may sometimes cause severe side effects, including high calcium levels (hypercalcemia). Your healthcare provider will monitor your calcium levels to ensure they do not become too high. Avoid calcium supplements and calcium-containing antacids while taking Phoslyra.

Let your healthcare provider know if you develop any signs of high calcium, including:

  • Constipation
  • Loss of appetite
  • Nausea
  • Vomiting
  • Headache
  • Confusion
  • Weakness or tiredness
  • Bone pain
  • Coma

Report Side Effects

Phoslyra may cause other side effects. Call your healthcare provider if you have any unusual problems while taking this medication.

If you experience a serious side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088).

Dosage: How Much Phoslyra Should I Take?

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The dose of this medicine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of this medicine. If your dose is different, do not change it unless your doctor tells you to do so.

The amount of medicine that you take depends on the strength of the medicine. Also, the number of doses you take each day, the time allowed between doses, and the length of time you take the medicine depend on the medical problem for which you are using the medicine.

  • For too much phosphate in the blood:
    • For oral dosage form (solution):
      • Adults—At first, the dose is usually 10 milliliters (mL) with each meal. The dose is adjusted by your doctor depending on how high your blood phosphorus level is.
      • Children—Use and dose must be determined by your doctor.
    • For oral dosage form (tablets):
      • Adults—2 tablets three times a day with meals. Your doctor may increase your dose if needed.
      • Children—Use and dose must be determined by your doctor.


The following modifications (changes) should be kept in mind when using Phoslyra:

Pregnancy: Phoslyra is not excepted to cause major birth defects or miscarriages. However, Phoslyra can cause high calcium levels, which can lead to pregnancy complications. Your healthcare provider will monitor your calcium levels closely throughout your pregnancy.

Breastfeeding: It is unknown what effect Phoslyra could have on a breastfed infant. Talk with your healthcare provider and pediatrician about the best way to feed your baby.

Adults over the age of 65 years: If you are over 65, your healthcare provider may start you on a low dose of Phoslyra and increase your dose slowly since you may be at increased risk of side effects.

Children: Phoslyra is not approved to treat children under the age of 18.

Missed Dose

If you forget to take a dose of Phoslyra, skip the missed dose and take your regular dose with your next meal. Do not double up or take extra Phoslyra.

Overdose: What Happens If I Take Too Much Phoslyra?

Overdosing on Phoslyra can cause your calcium levels to become too high (hypercalcemia), which may require emergency treatment. Signs of high calcium include constipation, loss of appetite, nausea, vomiting, confusion, delirium, and coma. If you've taken too much Phoslyra, contact your healthcare provider or the Poison Control Center right away. If your symptoms feel life-threatening, call 911.

What Happens If I Overdose on Phoslyra?

If you think you or someone else may have overdosed on Phoslyra, call a healthcare provider or the Poison Control Center (800-222-1222).

If someone collapses or isn't breathing after taking Phoslyra, call 911 immediately.


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It is very important that your doctor check your progress at regular visits, especially during the first few months of treatment with this medicine, since your dose may have to be adjusted. This is to make sure that this medicine is working properly and does not cause unwanted effects. Blood tests may be needed to check for unwanted effects.

Sometimes, you might have hypercalcemia (too much calcium in the blood) and not have any warning signs. You may need to have blood tests on a regular schedule while you are being treated with this medicine to check the amount of calcium and phosphorus in your blood. Keep all appointments your doctor makes for you.

If you have mild hypercalcemia, you may lose your appetite and have nausea, vomiting, or constipation. If the problem is severe, you may feel confused or extremely excited. Stop using this medicine and call your doctor right away if you think you might have severe hypercalcemia.

Do not take other calcium-containing products including dietary supplements and antacids. Your doctor may adjust the amount of calcium-containing foods you eat. Taking too much calcium while you are taking this medicine can cause hypercalcemia.

What Are Reasons I Shouldn’t Take Phoslyra?

You should not take Phoslyra if you have high calcium levels (hypercalcemia). Your healthcare provider will regularly monitor your calcium with a blood test to ensure your calcium levels remain in a healthy range.

What Other Medications Interact With Phoslyra?

Some medications may interact with Phoslyra. Be sure to inform your healthcare provider and pharmacist about all your medicines, including over-the-counter (OTC) products.

Do not take Phoslyra with other calcium medicines, including OTC supplements and antacids. Taking these medicines together can cause your calcium levels to become too high (hypercalcemia).

Phoslyra can prevent some medications from being absorbed. You may need to adjust when you take your medicine to avoid the interaction. Watch out for:

  • Fluoroquinolone antibiotics, such as Cipro (ciprofloxacin), Levaquin (levofloxacin), and Vigimox (moxifloxacin): Take at least two hours before or six hours after Phoslyra
  • Tetracycline antibiotics, such as Monodox (doxycycline) and Minocin (minocycline): Take at least one hour before Phoslyra
  • Synthroid (levothyroxine): Take at least four hours before or four hours after Phoslyra.

Many other medications may interact with Phoslyra. Always keep an up-to-date list of all your medicines, and let your healthcare provider and pharmacist know any time there are changes.

What Medications Are Similar?

Phoslyra belongs to a group of drugs called phosphate binders. They work by binding to phosphate and helping your body eliminate it. Other phosphate binders include:

  • Calcium carbonate
  • Renvela (sevelamer carbonate)
  • Renagel (sevelamer hydrochloride)
  • Fosrenol (lanthanum carbonate)
  • Velphoro (sucroferric oxyhydroxide)

Calcium-containing phosphate binders, such as Phoslyra and calcium carbonate, are inexpensive and lower phosphate levels effectively. However, high calcium levels can cause calcium crystals inside your blood vessels. This can increase your risk of high blood pressure, heart failure, and other health problems. Because of this risk, healthcare providers often prefer non-calcium-based phosphate binders, such as Renagel or Renvela.

Frequently Asked Questions

  • What is Phoslyra used for?

    Phoslyra is used to lower phosphate levels in adults with kidney failure on dialysis. Phoslyra should be used in combination with a low-phosphate diet.

  • How does Phoslyra work?

    Phoslyra is a phosphate binder. It works by attaching to phosphate, which helps your body eliminate it.

  • What drugs should not be taken with Phoslyra?

    Do not take calcium-containing supplements or antacids with Phoslyra. This could cause your calcium levels to become too high. Avoid taking certain antibiotics and levothyroxine at the same time as Phoslyra.

  • What are the side effects of Phoslyra?

    The most common side effects of Phoslyra include diarrhea, nausea, vomiting, and high calcium levels.

How Can I Stay Healthy While Taking Phoslyra?

If you have kidney failure, there can be a lot to manage. Keeping your phosphate levels in a healthy range is just one part of your treatment plan, but an important one. Most people will require a phosphate binder like Phoslyra to maintain a normal phosphate level, but you should also talk with your healthcare provider about a low-phosphate diet. Consider working with a registered dietitian (RD) or registered dietitian nutritionist (RDN) who specializes in kidney care (renal dietitian) to help you with any dietary changes.

Because Phoslyra can cause your calcium levels to become too high, it's essential to follow up with all blood work your healthcare provider orders. Discuss the symptoms of elevated calcium with your healthcare provider, and be sure to contact them if you notice any signs that your calcium might be too high. 

Medical Disclaimer

Verywell Health's drug information is meant for educational purposes only and not intended as a replacement for medical advice, diagnosis, or treatment from a healthcare provider. Consult your healthcare provider before taking any new medication(s). IBM Watson Micromedex provides some of the drug content, as indicated on the page.

7 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Christina Varvatsis, PharmD
Christina Varvatsis is a hospital pharmacist and freelance medical writer. She is passionate about helping individuals make informed healthcare choices by understanding the benefits and risks of their treatment options.