calcium Overview Information
Calcium is a mineral that is an essential part of bones and teeth. The heart, nerves, and blood-clotting systems also need calcium to work.
Calcium is used for treatment and prevention of low calcium levels and resulting bone conditions including osteoporosis (weak bones due to low bone density), rickets (a condition in children involving softening of the bones), and osteomalacia (a softening of bones involving pain). Calcium is also used for premenstrual syndrome (PMS), leg cramps in pregnancy, high blood pressure in pregnancy (pre-eclampsia), and reducing the risk of colon and rectal cancers.
Some people use calcium for complications after intestinal bypass surgery, high blood pressure, high cholesterol, Lyme disease, to reduce high fluoride levels in children, and to reduce high lead levels.
Calcium carbonate is used as an antacid for “heartburn.” Calcium carbonate and calcium acetate are also used for reducing phosphate levels in people with kidney disease.
Calcium-rich foods include milk and dairy products, kale and broccoli, as well as the calcium-enriched citrus juices, mineral water, canned fish with bones, and soy products processed with calcium.
Calcium can interact with many prescription medications, but sometimes the effects can be minimized by taking calcium at a different time. See the section titled “Are there any interactions with medications?"
How does it work?
The bones and teeth contain over 99% of the calcium in the human body. Calcium is also found in the blood, muscles, and other tissue. Calcium in the bones can be used as a reserve that can be released into the body as needed. The concentration of calcium in the body tends to decline as we age because it is released from the body through sweat, skin cells, and waste. In addition, as women age, absorption of calcium tends to decline due to reduced estrogen levels. Calcium absorption can vary depending on race, gender, and age.
Bones are always breaking down and rebuilding, and calcium is needed for this process. Taking extra calcium helps the bones rebuild properly and stay strong.
- Indigestion. Taking calcium carbonate by mouth as an antacid is effective for treating indigestion.
- High levels of potassium in the blood (hyperkalemia). Giving calcium gluconate intravenously (by IV) can reverse hyperkalemia, a condition in which there is too much potassium in the blood.
- Low levels of calcium in the blood (hypocalcemia). Taking calcium by mouth is effective for treating and preventing hypocalcemia. Also, giving calcium intravenously (by IV) is effective for treating very low levels of calcium.
- Kidney failure. Taking calcium carbonate or calcium acetate by mouth is effective for controlling high phosphate levels in the blood in people with kidney failure. Calcium citrate is not effective for treating this condition.
Likely Effective for:
- Osteoporosis caused by corticosteroid drugs. Taking calcium along with vitamin D seems to reduce the loss of bone mineral in people using corticosteroid drugs long-term.
- Increasing bone strength in fetuses. In pregnant women who eat a low amount of calcium as part of their diet, calcium supplementation increases the bone mineral density of the fetus. However, this does not appear to be beneficial for women with normal calcium levels.
- Parathyroid gland disorder (hyperparathyroidism). Taking calcium by mouth reduces parathyroid hormone levels in people with kidney failure and parathyroid hormone levels that are too high.
- Osteoporosis. Taking calcium by mouth is effective for preventing and treating bone loss and osteoporosis. Most bone growth occurs in the teenage years, and then bone strength in women remains about the same until age 30-40. After age 40, bone loss typically occurs at rates of 0.5% to 1% per year. In men, this bone loss occurs several decades later. There is more bone loss if less than the recommended amount of calcium is obtained from the diet. This is very common among Americans. Bone loss in women over 40 can be reduced by taking calcium supplements. Some researchers estimate that taking calcium for 30 years after menopause might result in a 10% improvement in bone strength and a 50% overall reduction in the rate of bone break.
- Reducing symptoms of premenstrual syndrome (PMS). There seems to be a link between low dietary calcium intake and symptoms of PMS. Consuming calcium daily seems to significantly reduce mood swings, bloating, food cravings, and pain. Also, increasing the amount of calcium in one’s diet seems to prevent PMS. Women consuming an average of 1283 mg/day of calcium from foods seem to have about a 30% lower risk of developing PMS than women who consume an average of 529 mg/day of calcium. Taking calcium supplements, however, does not seem to prevent PMS.
Possibly Effective for:
- Colorectal cancer. Research suggests that high intake of dietary or supplemental calcium reduces the risk of colorectal cancer. Research also shows that taking calcium supplements might help to keep colorectal cancer from returning. However, people with low levels of vitamin D do not seem to benefit from calcium supplements.
- Fluoride poisoning. Taking calcium by mouth, together with vitamin C and vitamin D supplements, seems to reduce fluoride levels in children and improve symptoms of fluoride poisoning.
- High cholesterol. Taking calcium supplements along with a low-fat or low-calorie diet seems to modestly reduce cholesterol. Taking calcium alone, without the restricted diet, does not seem to lower cholesterol.
- High blood pressure. taking calcium supplements seems to reduce blood pressure slightly (usually around 1-2 mmhg) in people with or without high blood pressure. calcium seems to be more effective in salt-sensitive people and people who normally get very little calcium. taking calcium by mouth also seems to be helpful for reducing blood pressure in people with serious kidney disease.
- Stroke. There is some evidence that increasing calcium intake in the diet might decrease the risk of stroke.
- High blood pressure during pregnancy (pre-eclampsia). Taking 1-2 grams of calcium by mouth daily seems to reduce pregnancy-related high blood pressure. Calcium appears to reduce the risk of high blood pressure in pregnancy by about 50%. Calcium appears to have the greatest effect in high-risk women and women with low calcium levels.
- Tooth loss. Taking calcium and vitamin D by mouth appears to help prevent tooth loss in older people.
- Weight loss. Adults and children with low calcium intake are more likely to gain weight, have a higher body mass index (BMI), and be overweight or obese compared to people with high calcium intake. Researchers have studied whether increasing calcium intake might help with weight loss. Some clinical research shows that increasing calcium consumption from dairy products, such as yogurt, increases weight loss, lean body mass, and body fat loss in people on a low-calorie diet as well as people on a regular unrestricted-calorie diet.
Possibly Ineffective for:
- Breast cancer. Some research suggests that women who eat more calcium have a reduced risk for developing breast cancer. However, other research suggests that blood levels of calcium are not linked with breast cancer risk. Overall, most research suggests that taking calcium does not reduce the risk for breast cancer.
- Heart disease. Evidence suggests that taking calcium supplements does not reduce the risk for heart disease in healthy people.
- Ovarian cancer. Some evidence suggests that high blood levels of calcium are linked to a reduced risk of ovarian cancer. However, other research suggests that dietary calcium intake is not linked with the risk of ovarian cancer.
- Cardiac arrest. Evidence suggests that administering calcium during cardiac arrest does not increase survival and might actually worsen the chance for resuscitation.
- Black widow spider bites. Some evidence suggests that injecting calcium intravenously (by IV) reduces muscle cramps associated with black widow spider bites.
- Cancer. Research shows that healthy older women who take 1400-1500 mg of calcium daily plus 1100 IU of vitamin D3 (cholecalciferol) daily have a 60% lower risk for developing cancer of any type. However, taking calcium alone does not seem to reduce the risk of cancer.
- Diabetes. Some early research suggests that consuming more calcium from the diet or from supplements, either alone or in combination with vitamin D, lowers the risk of developing type 2 diabetes.
- High levels of lead in the blood. Some research suggests that taking calcium supplements does not lower the levels of lead in the blood. However, other research suggests that taking calcium reduces blood lead levels by 11%.
- Endometrial cancer. Taking calcium supplements might reduce the risk of developing endometrial cancer. However, dietary calcium does not seem to have any benefit.
- Preventing falls. Evidence suggests that calcium plus vitamin D might help prevent falls by decreasing body sway and helping to keep blood pressure normal. Calcium alone does not seem to have the effect. Interestingly, calcium plus vitamin D seems to prevent falls in women, but not in men.
- Metabolic syndrome. Some evidence suggests that consuming more calcium from the diet and supplements, either alone or in combination with vitamin D, lowers the risk of developing metabolic syndrome.
- Vitamin B12 deficiency caused by the drug metformin. Taking calcium supplements might reduce vitamin B12 deficiency caused by the diabetes drug metformin.
- Inflammation in the digestive tract (mucositis). Evidence suggests that using a mouth rinse containing calcium phosphate (Caphosol) in combination with fluoride treatments reduces the duration of pain in people with inflammation in the digestive tract.
- Depression after pregnancy (postpartum depression). Early research suggests that taking calcium daily, beginning 11-21 weeks into pregnancy, reduces depression 12 weeks after delivery.
- Pregnancy-related leg cramps. Early research shows that calcium can help prevent leg cramps in the second half of pregnancy.
- Prostate cancer. Research about how calcium affects the risk of prostate cancer has shown conflicting results. Some research suggests that taking calcium supplements daily decreases the risk of prostate cancer. However, other research suggests that there is not a link between calcium intake and the risk for developing prostate cancer.
- Seizures. Early research suggests that calcium might help control seizures caused by sudden drops in blood levels of calcium.
- Lyme disease.
- Other conditions.
calcium Side Effects & Safety
Calcium is LIKELY SAFE for most people when taken by mouth or when given intravenously (by IV) and appropriately. Calcium can cause some minor side effects such as belching or gas.
Calcium is POSSIBLY UNSAFE for both adults and children when taken by mouth in high doses. Avoid taking too much calcium. The Institute of Medicine sets the daily tolerable upper intake level (UL) for calcium based on age as follows: Age 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-8 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg. Higher doses increase the chance of having serious side effects. Some recent research also suggests that doses over the recommended daily requirement of 1000-1300 mg daily for most adults might increase the chance of heart attack. This research is concerning, but it is still too soon to say for certain that calcium is truly the cause of heart attack. Until more is known, continue consuming adequate amounts of calcium to meet daily requirements, but not excessive amounts of calcium. Be sure to consider total calcium intake from both dietary and supplemental sources and try not to exceed 1000-1300 mg of calcium per day. To figure out dietary calcium, count 300 mg/day from non-dairy foods plus 300 mg/cup of milk or fortified orange juice.
Special Precautions & Warnings:Pregnancy and breast-feeding: Calcium is LIKELY SAFE when taken by mouth in recommended amounts during pregnancy and breast-feeding. There is not enough information available on the safety of using calcium intravenously (by IV) during pregnancy and breastfeeding.
Low acid levels in the stomach (achlorhydria). People with low levels of gastric acid absorb less calcium if calcium is taken on an empty stomach. However, low acid levels in the stomach do not appear to reduce calcium absorption if calcium is taken with food. Advise people with achlorhydria to take calcium supplements with meals.
High levels of phosphate in the blood (hyperphosphatemia) or low levels of phosphate in the blood (hypophosphatemia): Calcium and phosphate have to be in balance in the body. Taking too much calcium can throw this balance off and cause harm. Don’t take extra calcium without your health provider’s supervision.
Under-active thyroid (hypothyroidism): Calcium can interfere with thyroid hormone replacement treatment. Separate calcium and thyroid medications by at least 4 hours.
Too much calcium in the blood (as in parathyroid gland disorders and sarcoidosis): Calcium should be avoided if you have one of these conditions.
Poor kidney function: Calcium supplementation can increase the risk of having too much calcium in the blood in people with poor kidney function.
Smoking: People who smoke absorb less calcium from the stomach.
Major Interaction Do not take this combination
- Ceftriaxone (Rocephin) interacts with CALCIUM
Administering intravenous ceftriaxone and calcium can result in life-threatening damage to the lungs and kidneys. Calcium should not be administered intravenously within 48 hours of intravenous ceftriaxone.
Moderate Interaction Be cautious with this combination
- Antibiotics (Quinolone antibiotics) interacts with CALCIUM
Calcium might decrease how much antibiotic your body absorbs. Taking calcium along with some antibiotics might decrease the effectiveness of some antibiotics. To avoid this interaction, take calcium supplements at least 1 hour after antibiotics.
Some of these antibiotics that might interact with calcium include ciprofloxacin (Cipro), enoxacin (Penetrex), norfloxacin (Chibroxin, Noroxin), sparfloxacin (Zagam), and trovafloxacin (Trovan).
- Antibiotics (Tetracycline antibiotics) interacts with CALCIUM
Calcium can attach to some antibiotics called tetracyclines in the stomach. This decreases the amount of tetracyclines that can be absorbed. Taking calcium with tetracyclines might decrease the effectiveness of tetracyclines. To avoid this interaction take calcium 2 hours before or 4 hours after taking tetracyclines.
Some tetracyclines include demeclocycline (Declomycin), minocycline (Minocin), and tetracycline (Achromycin, and others).
- Bisphosphonates interacts with CALCIUM
Calcium can decrease how much bisphosphate your body absorbs. Taking calcium along with bisphosphates can decrease the effectiveness of bisphosphate. To avoid this interaction, take bisphosphonate at least 30 minutes before calcium or later in the day.
Some bisphosphonates include alendronate (Fosamax), etidronate (Didronel), risedronate (Actonel), tiludronate (Skelid), and others.
- Calcipotriene (Dovonex) interacts with CALCIUM
Calcipotriene (Dovonex) is a drug that is similar to vitamin D. Vitamin D helps your body absorb calcium. Taking calcium supplements along with calcipotriene (Dovonex) might cause the body to have too much calcium.
- Digoxin (Lanoxin) interacts with CALCIUM
Calcium can affect your heart. Digoxin (Lanoxin) is used to help your heart beat stronger. Taking calcium along with digoxin (Lanoxin) might increase the effects of digoxin (Lanoxin) and lead to an irregular heartbeat. If you are taking digoxin (Lanoxin), talk to your doctor before taking calcium supplements.
- Diltiazem (Cardizem, Dilacor, Tiazac) interacts with CALCIUM
Calcium can affect your heart. Diltiazem (Cardizem, Dilacor, Tiazac) can also affect your heart. Taking large amounts of calcium along with diltiazem (Cardizem, Dilacor, Tiazac) might decrease the effectiveness of diltiazem (Cardizem, Dilacor, Tiazac).
- Levothyroxine interacts with CALCIUM
Levothyroxine is used for low thyroid function. Calcium can decrease how much levothyroxine your body absorbs. Taking calcium along with levothyroxine might decrease the effectiveness of levothyroxine. Levothyroxine and calcium should be taken at least 4 hours apart.
Some brands that contain levothyroxine include Armour Thyroid, Eltroxin, Estre, Euthyrox, Levo-T, Levothroid, Levoxyl, Synthroid, Unithroid, and others.
- Sotalol (Betapace) interacts with CALCIUM
Taking calcium with sotalol (Betapace) can decrease how much sotalol (Betapace) your body absorbs. Taking calcium along with sotalol (Betapace) might decrease the effectiveness of sotalol (Betapace). To avoid this interaction, take calcium at least 2 hours before or 4 hours after taking sotalol (Betapace).
- Verapamil (Calan, Covera, Isoptin, Verelan) interacts with CALCIUM
Calcium can affect your heart. Verapamil (Calan, Covera, Isoptin, Verelan) can also affect your heart. Do not take large amounts of calcium if you are taking verapamil (Calan, Covera, Isoptin, Verelan).
- Water pills (Thiazide diuretics) interacts with CALCIUM
Some "water pills" increase the amount of calcium in your body. Taking large amounts of calcium with some "water pills" might cause there to be too much calcium in the body. This could cause serious side effects, including kidney problems.
Some of these "water pills" include chlorothiazide (Diuril), hydrochlorothiazide (HydroDIURIL, Esidrix), indapamide (Lozol), metolazone (Zaroxolyn), and chlorthalidone (Hygroton).
Minor Interaction Be watchful with this combination
- Estrogens interacts with CALCIUM
Estrogen helps your body absorb calcium. Taking estrogen pills along with large amounts of calcium might increase calcium in the body too much.
Estrogen pills include conjugated equine estrogens (Premarin), ethinyl estradiol, estradiol, and others.
- Medications for high blood pressure (Calcium channel blockers) interacts with CALCIUM
Some medications for high blood pressure affect calcium in your body. These medications are called calcium channel blockers. Getting calcium injections might decrease the effectiveness of these medications for high blood pressure.
Some medications for high blood pressure include nifedipine (Adalat, Procardia), verapamil (Calan, Isoptin, Verelan), diltiazem (Cardizem), isradipine (DynaCirc), felodipine (Plendil), amlodipine (Norvasc), and others.
The following doses have been studied in scientific research:
- For preventing low calcium levels: 1 gram elemental calcium daily is typically used.
- For heartburn: Calcium carbonate as an antacid is usually 0.5-1.5 grams as needed.
- To reduce phosphates in adults with chronic renal failure: The initial dose of calcium acetate is 1.334 grams (338 mg elemental calcium) with each meal, increasing to 2-2.67 grams (500-680 mg elemental calcium) with each meal if necessary.
- For prevention of weak bones (osteoporosis): Doses of 1-1.6 grams elemental calcium daily from foods and supplements. Osteoporosis treatment guidelines in North America currently recommend 1200 mg daily of calcium.
- For prevention of bone loss in premenopausal women over 40: A dose of 1 gram.
- For pregnant women with low dietary calcium intake: The dose for increasing fetal bone density ranges from 300-1300 mg/day beginning at gestation week 20-22.
- For premenstrual syndrome (PMS): 1-1.2 grams calcium per day as calcium carbonate.
- For reducing thyroid hormone levels in people with chronic renal failure: 2-21 grams calcium carbonate.
- To prevent bone loss in people taking corticosteroid drugs: Divided daily doses of 1 gram of elemental calcium daily.
- For high blood pressure: 1-1.5 grams calcium daily.
- For preventing high blood pressure during pregnancy (pre-eclampsia): 1-2 grams elemental calcium daily as calcium carbonate.
- For preventing colorectal cancer and recurrent colorectal benign tumors (adenomas): Calcium 1200-1600 mg/day.
- For high cholesterol: 1200 mg daily with or without vitamin D 400 IU daily has been used in conjunction with a low-fat or calorie-restricted diet.
- For preventing fluoride poisoning in children: Calcium 125 mg twice daily, in combination with ascorbic acid and vitamin D.
- For weight loss, increasing calcium consumption from dairy products to total intake of 500-2400 mg/day in combination with a calorie-restricted diet has been used.
Calcium supplements are usually divided into two doses daily in order to increase absorption. It’s best to take calcium with food in doses of 500 mg or less.
The Institute of Medicine publishes a recommended daily allowance (RDA) for calcium which is an estimate of the intake level necessary to meet the requirements of nearly all healthy individuals in the population. The current RDA was set in 2010. The RDA varies based on age as follows: Age 1-3 years, 700 mg; 4-8 years, 1000 mg; 9-18 years, 1300 mg; 19-50 years, 1000 mg; Men 51-70 years, 1000 mg; Women 51-70 years, 1200 mg; 70+ years, 1200 mg; Pregnant or Lactating (under 19 years), 1300 mg; Pregnant or Lactating (19-50 years), 1000 mg.
The Institute of Medicine also sets the daily tolerable upper intake level (UL) for calcium based on age as follows: Age 0-6 months, 1000 mg; 6-12 months, 1500 mg; 1-3 years, 2500 mg; 9-18 years, 3000 mg; 19-50 years, 2500 mg; 51+ years, 2000 mg. Doses above these levels should be avoided.
Doses over the recommended daily intake level of 1000-1300 mg/day for most adults have been associated with an increased risk of heart attack. Until more is known, continue consuming adequate amounts of calcium to meet daily requirements, but not excessive amounts of calcium. Be sure to consider total calcium intake from both dietary and supplemental sources and try not to exceed 1000-1300 mg of calcium per day. To figure out dietary calcium, count 300 mg/day from non-dairy foods plus 300 mg/cup of milk or fortified orange juice.