Calcium acetate: dosage, uses, side effects

You’re probably familiar with the natural element, calcium. After all, it’s the most abundant mineral in the human body and is essential for your bones and teeth as well as numerous other vital bodily functions. But did you know that there are variations of calcium like calcium carbonate and calcium acetate?

Calcium is found in foods, dietary supplements, and prescription medications. When calcium binds to other compounds, it can form salts that the body can absorb and use, like calcium carbonate (Tums). Each calcium salt contains varying amounts of elemental calcium and has different effects on the body (NIH-a, 2021). 

Calcium acetate is not a form of calcium that’s found in an over-the-counter supplement or antacid (like calcium carbonate). It’s a prescription drug that healthcare providers use to treat end-stage chronic kidney disease (CKD) in people on dialysis.

Read on to learn more about calcium acetate (brand name: PhosLo), its side effects, dosage, and more.

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Calcium acetate is a generic prescription drug. It also goes by its brand names: PhosLo, Eliphos, and Phoslyra (FDA, n.d.).

It belongs to a class of drugs called phosphorus or phosphate binders. (Note: phosphate is a form of phosphorus, and the terms are used interchangeably.) Phosphate or phosphorus is an essential mineral that helps the body maintain strong bones and repair cells. Calcium acetate works to lower phosphate levels in the blood in people with end-stage chronic kidney disease (CKD) who are on dialysis (NIH-b, 2021; Fresenius, 2011). 

CKD is a condition in which your kidneys gradually lose their function as your blood’s filtration system (meaning, the body has a harder time filtering out things like excess phosphate). It affects 47 million people in the United States (Gaitonde, 2017). In the later stages of CKD, dialysis becomes a necessary procedure to remove excess fluid, electrolytes, and toxins from your blood (Vaidya, 2021).

Calcium acetate works by binding to phosphate from the diet, forming a complex that the body cannot absorb so that it can pass out of your body. This helps prevent CKD mineral and bone disorder (a condition that causes thin, weak bones and heart complications). It is taken before a meal to prevent the body from absorbing phosphorus from foods (Fresnius, 2011).

Some examples of foods that contain phosphorus are meats, fish, eggs, nuts, vegetables, and grains (NIH-b, 2021).

The Food and Drug Administration (FDA) approves the use of calcium acetate (PhosLo) to treat high levels of phosphate in the blood in adults with end-stage chronic kidney disease (CKD) or renal failure on dialysis. The medical term for this condition is hyperphosphatemia (Fresenius, 2011).

Sometimes, healthcare providers will prescribe calcium acetate for a use different from what the FDA approves it for, also known as an “off-label” prescription.

For example, a doctor may use calcium acetate off-label to treat hyperphosphatemia caused by tumor lysis syndrome (TLS). TLS can be a side effect of certain cancer treatments. It occurs when cancer cells are destroyed and rapidly release their contents, including phosphate, into the blood faster than the kidneys can remove them (Goyal, 2021; Gupta, 2018).

Common side effects of calcium acetate include (Fresenius, 2011):

• Nausea

• Vomiting

• Diarrhea

• Mild hypercalcemia (slightly elevated calcium level in the blood), which may cause symptoms like constipation, loss of appetite, nausea, or vomiting. 

Less frequently, people experience serious side effects such as severe hypercalcemia (very high blood calcium level), which may cause serious symptoms like confusion, delirium, and coma.

This medication is available in tablets, gelcaps (gel-coated capsules), and an oral liquid solution. It comes in 667 mg per tablet, gelcap, or teaspoon (Fresenius, 2011). 

The typical starting dose is two tablets, gelcaps, or teaspoons (total of 1,334 mg) before each meal. Your healthcare provider may increase your dose every two to three weeks. They’ll determine your dose based on your blood phosphate levels, so you’ll have to get blood tests at least twice a week at first while they adjust your dosage.

Calcium acetate can potentially prevent certain medications from working by binding to them after you swallow them. In most cases, you can manage these interactions by taking the other medication one hour before or three hours after calcium acetate. Some examples include (Fresenius, 2011):

• Certain antibiotics like tetracyclines (e.g., doxycycline and minocycline) and fluoroquinolones (e.g., ciprofloxacin and levofloxacin)

• Heart medications like digoxin

• Anti-seizure medications 

Taking certain medications can make your calcium levels too high if you’re also taking calcium acetate. If your healthcare provider prescribes any of these medications to you, be sure to follow their instructions for having your blood tested to monitor your calcium levels. Examples include over-the-counter calcium supplements and antacids that contain calcium like Tums.

The lists above do not include all of the potential drug interactions with calcium acetate. Your healthcare professional and pharmacist will want to know all of the drugs and supplements you’re currently taking. They can provide medical advice to manage any interactions or side effects of your medications.

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Current version

November 03, 2021

Written by

Patricia Weiser, PharmD

Fact checked by

Felix Gussone, MD

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About the medical reviewer

Felix Gussone, MD, Ro

Felix Gussone is a physician, health journalist and a Manager, Medical Content & Education at Ro.