If you are currently being treated with any of the following medications, you
should not use calcium supplements without first talking to your healthcare
Calcium may interfere with the absorption of
alendronate, a medication used to treat osteoporosis. Calcium containing
products, therefore, should be taken at least two hours before or after
When calcium citrate is taken
with aluminum containing antacids, the amount of aluminum absorbed into the
blood stream may be increased significantly. This is a particular problem for
people with kidney disease in whom the aluminum levels may become toxic. In
addition, aluminum-containing antacids may increase the loss of calcium in the
Blood Pressure Medications
Taking calcium with a beta-blocker
(such as atenolol), a group of medications used for the treatment of high blood
pressure or heart disorders, may interfere with blood levels of both the calcium
and the beta-blocker. Study results are conflicting, however. Until more is
known, individuals taking atenolol, or another beta blocker, should have their
blood pressure checked before and after adding calcium supplements or calcium
containing antacids to their medication regimen.
Similarly, it has been reported that calcium may reverse the therapeutic
effects as well as the side effects of calcium channel blockers (such as
verapamil) often prescribed for the treatment of high blood pressure. These
study results are also controversial. People taking verapamil or another calcium
channel blocker along with calcium supplements should likely have their blood
pressure checked regularly.
A class of medications known
as bile acid sequestrants (including cholestyramine, colestipol, and
colesevelam), used to treat high cholesterol, may interfere with normal calcium
absorption and increase the loss of calcium in the urine. Supplementation,
therefore, with calcium and vitamin D may be recommended by your healthcare
Corticosteroid medications reduce the
absorption of calcium, thereby increasing the risk for bone loss and
osteoporosis over time. This is of particular concern for anyone who is
maintained on long-term steroids.
High levels of calcium may increase the likelihood of
a toxic reaction to digoxin, a medication used to treat irregular heart rhythms.
On the other hand, low levels of calcium cause this medication to be
ineffective. People who are taking digoxin should have calcium levels monitored
in the blood closely.
Two different classes of diuretics interact with
calcium in opposite ways—thiazide diuretics such as
hydrochlorothiazide can raise calcium levels in the blood, while loop diuretics,
such as furosemide and bumetanide, can decrease calcium levels. In addition,
amiloride, a potassium-sparing diuretic, may decrease the amount of calcium
excreted in the urine (and subsequently increase calcium levels in the blood),
especially in people with kidney stones.
Estrogens may contribute to an overall increase in
calcium blood levels. Taking calcium supplements together with estrogens
improves gain in bone density significantly.
Taking calcium during treatment with the antibiotic
gentamicin may increase the potential for toxic effects on the kidneys.
Metformin, a medication used to treat type 2
diabetes, can deplete levels of vitamin B12. Some early evidence suggests that
calcium supplements may prevent or eliminate this negative effect of metformin.
More research is needed.
Calcium can interfere with the body's
ability to absorb quinolone antibiotics (such as ciprofloxacin, levofloxacin,
norfloxacin, and ofloxacin). If taking calcium containing supplements or
antacids, therefore, you should take them two to four hours before or after
taking quinolone antibiotics.
Low levels of calcium have been reported
with high doses of seizure medications, such as phenytoin, which may decrease
calcium absorption. Some physicians recommend vitamin D along with anti-seizure
drugs to try to prevent the development of low calcium levels.
Calcium can interfere with the body's ability to
absorb tetracycline medications (including doxycycline, minocycline, and
tetracycline) and, therefore, diminish their effectiveness. Calcium containing
supplements and antacids should be taken at least two hours before or after
taking these drugs.