Calcium
Over-the-counterWhat is Calcium?
Calcium is an essential mineral your body needs for strong bones and teeth. It also helps your muscles contract, your nerves send signals, and your blood clot properly. Your body cannot make calcium on its own, so you need to get it from food or supplements.
Most adults need between 1,000 and 1,200 milligrams of calcium each day. Many people do not get enough calcium from their diet alone. Calcium supplements can help fill this gap and prevent bone loss over time.
Calcium supplements come in several forms including calcium carbonate and calcium citrate. Each type is absorbed differently by your body. Taking calcium with vitamin D helps your body absorb and use the mineral more effectively.
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Common uses
- Preventing and treating low calcium levels in people who do not get enough from their diet
- Reducing bone loss in people with osteoporosis or at risk for weak bones
- Supporting bone health during pregnancy and breastfeeding
- Treating conditions that cause low calcium such as hypoparathyroidism
- Managing symptoms of premenstrual syndrome
- Supporting healthy blood pressure levels
How it works
Calcium works by providing your body with the mineral it needs to build and maintain bone tissue. About 99 percent of the calcium in your body is stored in your bones and teeth. The remaining 1 percent circulates in your blood and helps with vital functions like muscle contraction and nerve signaling.
When your blood calcium levels drop too low, your body takes calcium from your bones to maintain normal function. Over time, this can weaken your bones and increase fracture risk. Taking calcium supplements helps keep your blood levels stable and protects your bone density. Vitamin D helps your intestines absorb calcium from food and supplements more efficiently.
Taking Calcium? Monitor your levels.
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Dosage information
Most adults need 1,000 to 1,200 milligrams of calcium daily from all sources including food and supplements. Women over 50 and men over 70 typically need 1,200 milligrams per day. Your body absorbs calcium best in doses of 500 milligrams or less, so split larger doses throughout the day. Take calcium carbonate with food for best absorption. You can take calcium citrate with or without food. Always follow the dosing instructions on your supplement label.
Side effects
- Gas and bloating
- Constipation
- Upset stomach
- Nausea
Taking too much calcium can cause serious problems including kidney stones, high blood calcium levels, and heart rhythm issues. Contact your doctor if you experience severe stomach pain, increased thirst, frequent urination, confusion, or muscle weakness. Do not take more than 2,000 to 2,500 milligrams of calcium per day from all sources unless your doctor tells you to.
Drug interactions
- Calcium can reduce absorption of thyroid medications like levothyroxine. Take thyroid medicine at least 4 hours before or after calcium.
- Antibiotics including tetracyclines and fluoroquinolones may not work as well when taken with calcium. Separate doses by at least 2 hours.
- Calcium can interfere with bisphosphonates used for osteoporosis. Take bisphosphonates at least 30 minutes before calcium.
- Thiazide diuretics can increase calcium levels in your blood when combined with calcium supplements.
- High doses of calcium may reduce absorption of iron, zinc, and magnesium supplements.
- Corticosteroids can decrease calcium absorption and increase calcium loss from bones.
Blood test monitoring
Regular blood tests help ensure your calcium levels stay in a healthy range. Your doctor may check your blood calcium levels, especially if you take high doses or have kidney problems. Testing vitamin D levels is also important because low vitamin D can prevent your body from absorbing calcium properly. Some people may need parathyroid hormone testing if their calcium levels are consistently abnormal. Rite Aid offers blood testing services that measure calcium, vitamin D, and over 200 other biomarkers. Getting tested twice a year helps you and your doctor adjust your supplement dose if needed.
Related blood tests
Taking Calcium? Monitor your levels.
- Track how your body responds
- Catch side effects early with blood work
- Share results with your doctor
Frequently asked questions
Yes, calcium supplements are available over the counter at Rite Aid and other pharmacies. You do not need a prescription to purchase calcium supplements. However, talk to your doctor before starting any new supplement, especially if you have kidney problems or take other medications.
Calcium carbonate contains more elemental calcium per pill but needs stomach acid to be absorbed well. Take it with food for best results. Calcium citrate is absorbed easily with or without food and works better for people with low stomach acid or those taking acid reducers. Both forms are effective when taken correctly.
Most adults need 1,000 to 1,200 milligrams daily from food and supplements combined. Women over 50 and men over 70 need 1,200 milligrams per day. Do not exceed 2,000 to 2,500 milligrams daily from all sources as this can cause health problems.
Yes, taking calcium with vitamin D is highly recommended. Vitamin D helps your intestines absorb calcium more effectively. Many calcium supplements already include vitamin D for this reason. If your supplement does not contain vitamin D, consider taking a separate vitamin D supplement.
The best time depends on the type of calcium you take. Take calcium carbonate with meals for better absorption. You can take calcium citrate any time with or without food. Split doses of more than 500 milligrams throughout the day because your body absorbs smaller amounts more efficiently.
Yes, taking too much calcium can cause kidney stones, constipation, and high blood calcium levels. Very high levels may interfere with heart and brain function. Stick to recommended doses and talk to your doctor before taking more than 1,200 milligrams daily from supplements.
Regular blood tests can help monitor your calcium and vitamin D levels to ensure they stay in a healthy range. Testing is especially important if you take high doses, have kidney disease, or experience symptoms of high calcium. Rite Aid offers blood testing services that check calcium, vitamin D, and parathyroid hormone levels twice a year.
Calcium can slow down movement in your digestive tract, leading to constipation in some people. Calcium carbonate is more likely to cause this side effect than calcium citrate. Drinking plenty of water, eating fiber-rich foods, and staying active can help prevent constipation while taking calcium.
Some people can meet their calcium needs through diet by eating dairy products, leafy greens, and fortified foods. However, many adults do not consume enough calcium-rich foods daily. A supplement can help fill the gap if your diet falls short of the 1,000 to 1,200 milligrams you need each day.
Calcium supplements can help slow bone loss and reduce fracture risk, especially when combined with vitamin D and weight-bearing exercise. They work best for people who do not get enough calcium from their diet. However, supplements alone cannot guarantee strong bones. A healthy lifestyle including regular exercise and adequate protein intake is also important.