What You Need to Know About Calcium Supplements

Calcium helps build strong bones, but the value of calcium supplements has been questioned.


The advice is simple: to keep bones strong and ward off osteoporosis, especially as you age, get enough calcium – 1,000 milligrams (mg) per day if you’re younger than 50; 1,200 mg if you’re older. You can get calcium in your diet by eating green leafy vegetables; consuming low-fat milk, yogurt and cheese; or opting for calcium-fortified juice, bread and cereal. Or if you don’t get enough calcium in your diet, a calcium supplement may be in order. But are supplements worth it? Yes and no, say experts.

Too much calcium can be a bad thing. Excess amounts (more than 2,500 mg a day) can harm the kidneys and can reduce the absorption of other minerals like iron, zinc and magnesium.

Clifford J. Rosen, MD, a senior scientist at the Maine Medical Center Research Institute in Scarborough, was part of a committee that set the U.S. calcium intake recommendations through the Institute of Medicine, or IOM, in 2010. The committee discovered that the majority of Americans are getting between 750 mg and 900 mg of calcium through diet alone.

“You don’t need to go crazy taking calcium supplements,” says Donald Miller, PharmD, chair of the department of pharmacy practice at North Dakota State University in Fargo. “Talk to your doctor and find out if you need to take a calcium supplement before going out on your own. Americans love to take supplements and think, ‘Well, it can’t hurt.’”

But actually it could. Dr. Rosen says you don’t want to get too much calcium because there’s a risk of kidney stones and possible cardiovascular risk, which is currently being studied.

A 2012 study in Heart suggested that taking calcium supplements nearly doubled the risk of heart attack. The researchers suggested that calcium from supplements may be problematic for the cardiovascular system because it causes a spike in blood calcium levels, versus the gradual rise that occurs when calcium is obtained from food.

However, millions of people depend on calcium supplements to keep osteoporosis at bay – especially people with rheumatoid arthritis and other inflammatory forms of the disease. For a variety of reasons, including corticosteroid use and limited activity, they are at increased risk of developing osteoporosis.

Reena L. Pande, MD, a cardiovascular specialist at Brigham and Women’s Hospital in Boston, says that this is one of those situations in which it is important for patients to talk with their doctors.

“Everyone is different,” Dr. Pande says. “For example, for a patient with osteoporosis, or with a specific condition that might be strongly linked with the development of osteoporosis, the benefit of calcium supplementation might outweigh the potential heart risk.”

The takeaway message is to try to get as much calcium through your diet as you can, and talk to your doctor before taking a calcium supplement.

Calcium Supplement Basics

If your doctor recommends you take a calcium supplement, here are some tips to know before you buy:

1. Understand how much calcium you are getting through your diet before you take supplements. Taking too much can be bad for you.

2. Take several smaller doses per day, because your body can absorb only 500 mg at a time.

3. Your body needs vitamin D to use calcium most efficiently, so look for supplements that contain both.

Calcium “Cheat Sheet”
There are several different types of calcium. Check out the chart below for the three most popular types, and to help determine the best calcium supplement for you. Other kinds, such as calcium gluconate and calcium lactate, have very low amounts of elemental calcium and are not recommended. Coral calcium and oyster-shell calcium products also are best avoided because they may contain lead.

Calcium Type 



Calcium citrate
(Citrical, Solgar) 21% calcium

Most easily absorbed

Most expensive; doesn’t contain much elemental calcium

Calcium carbonate
(Tums, Caltrate, Rolaids) 40% calcium 

Least expensive; has more elemental calcium

Must be taken with meals or glass of acidic (orange) juice; may cause gas or constipation

Calcium phosphate (Posture) 39% calcium 

Does not cause gas or constipation; easily absorbed

More expensive than calcium carbonate

Precautions: Don’t take more than 1,200 mg of calcium (in supplement form) a day unless instructed by a doctor or dietitian. Also, avoid taking calcium supplements at the same time as some kinds of medications, including bisphosponates like alendronate (Fosamax) and ibandronate (Boniva) and certain antibiotics, because it can block their absorption by the body. As with any supplement, talk to your doctor before taking.