Intestinal aluminum absorption is increased in healthy and kidney failure patients taking even small amounts of calcium citrate. As a result, all citrate-containing preparations are contraindicated in chronic renal failure patients taking aluminum-containing compounds.
Intake of a bisphosphonate and calcium may decrease the absorption of the bisphosphonate. Patients should take bisphosphonates at least 30 minutes before calcium. Optimally, the two would be consumed at different times of the day.
Caffeine may increase urinary calcium excretion and has been implicated in osteoporosis; however, research is still conflicting. Caffeine has a small effect on calcium absorption.
Calcitriol is a form of vitamin D that is used to treat and prevent low levels of calcium in the blood of patients whose kidneys or parathyroid glands (glands in the neck that release natural substances to control the amount of calcium in the blood) are not working normally.
When given intravenously, calcium can reverse the effects of calcium channel blockers (commonly used for high blood pressure). Calcium channel blockers include: nifedipine (Adalat®, Procardia®), verapamil (Calan®, Isopin®, Verelan®), diltiazem (Cardizem®), isradipine (DynaCirc®), felodipine (Plendil®), and amlodipine (Norvasc®).
Corticosteroids (commonly used for inflammation) can cause significant bone loss (osteoporosis) if the recommended level of calcium and vitamin D intake is not met.
Calcium levels should be monitored if taking the heart rhythm medication digoxin due to the potential for interaction with high blood levels of calcium and the need for adequate blood levels of calcium. Patients taking digoxin should consult with a qualified healthcare professional before using calcium supplements.
Alcohol can affect calcium status by reducing the intestinal absorption of calcium. It can also inhibit enzymes in the liver that help convert vitamin D to its active form, which in turn reduces calcium absorption. However, the amount of alcohol required to affect calcium absorption is unknown. Evidence is currently conflicting on whether moderate alcohol consumption is helpful or harmful to bone.
Fluroquinolone antibiotics form complexes with calcium in the gastrointestinal tract, which can lead to reduced absorption of both if taken at the same time.
Hormone replacement therapy (HRT) alone may be associated with a fall in calcium absorption efficiency. However, the bone-preserving effects of estrogen treatment are increased by calcium supplementation. Estrogen increases supplemental calcium absorption in postmenopausal women.
Use of inositol hexaphosphate (phytic acid) and calcium may decrease the absorption of calcium.
Intake of levothyroxine (synthroid, levothroid, levoxyl) at the same time as calcium carbonate has been found to reduce levothyroxine absorption and to increase serum thyrotropin levels. Levothyroxine may adsorb (stick) to calcium carbonate in an acidic environment, which may block its absorption.
Loop diuretics, including furosemide (Lasix®), bumetanide (Bumex®), ethracrynic acid (Edecrin®), and torsemide (Demadex®), at high doses, may reduce serum calcium levels because they increase urinary calcium excretion.
Orlistat (Xenical®) has been shown to induce a relative increase in bone turnover (increased resorption or bone loss), which may be due to the malabsorption of vitamin D and/or calcium.
The effect of dietary phosphorus on calcium is minimal. Some researchers speculate that the detrimental effects of consuming foods high in phosphate such as carbonated soft drinks is due to the replacement of milk with soda rather than the phosphate level itself.
Use of proton pump inhibitors (like esomeprazole used to treat ulcers) and calcium carbonate or calcium phosphate at the same time can cause decreased absorption of these calcium salts.
Typically, dietary sodium and protein increase calcium excretion as their intake is increased. However, if a high protein, high sodium food also contains calcium, this may help counteract the loss of calcium.
Calcium may form complexes with sotalol (a beta-blocker drug used to treat irregular heartbeats), reducing its absorption. A physician should be contacted in order to determine optimal timing of doses. Patients taking sotalol should consult a qualified healthcare professional before using calcium supplements.
Intake of a tetracycline and calcium may decrease the absorption of the tetracycline, including doxycycline, minocycline, and tetracycline. Two to four hours between tetracyclines and calcium supplements should be allowed.
Thiazides are diuretics that reduce calcium excretion by the kidneys. These diuretics include: chlorothiazide (Diuril®), hydrochlorothiazide (HydroDIURIL®, Esidrix®), indapamide (Lozol®), metolazone (Zaroxolyn®), and chlorthalidone (Hygroton®).
An interaction between levothyroxine (a thyroid hormone) and calcium carbonate is also possible.
Calcium carbonate and aluminum hydroxide taken together have produced a significant rise in serum and urine aluminum levels.
Combined use of inositol hexaphosphate (phytic acid) and calcium may decrease the absorption of calcium.
Inulin, found in fresh cheese, does not appear to acutely affect serum ionized calcium concentrations.
Stimulant laxatives (cascara, senna, and bisacodyl) when used for prolonged periods can reduce dietary calcium and vitamin D absorption often causing osteomalacia (bone softening).
Combining calcium salts may increase absorption or alter efficacy.
Large doses of magnesium salts can cause hypocalcaemia (low levels of blood calcium). Oral magnesium supplements do not affect calcium absorption.
Combined use of iron and calcium may not inhibit the absorption of iron over long periods of time. Combined use of fluoride, magnesium, or zinc and calcium may decrease the absorption of these minerals. However, these possible mineral interactions have not been shown to be of clinical significance.
Mineral oil can interfere with calcium utilization and retention by reducing the absorption of calcium and vitamin D.
Combined use of non-digestible fructo-oligosaccharides or inulin and calcium may increase the absorption of calcium in the colon.
Calcium taken orally can bind with phosphate in the gut, preventing its absorption and reducing the hyperphosphatemia (high levels of phosphate in the blood) associated with renal failure. Calcium carbonate or calcium acetate is used for this purpose, whereas calcium citrate is not recommended because it increases aluminum absorption.
While the effects of high phosphorus intakes on calcium balance and bone health are presently unclear, the substitution of large quantities of soft drinks for milk or other sources of dietary calcium is cause for concern with respect to bone health in adolescents and adults. The effect of dietary phosphorus on calcium is minimal.
Reports show that increased sodium intake results in increased loss of calcium in the urine suggesting that an effect of reducing bone loss by increasing calcium supplementation can also be achieved by halving daily sodium excretion.
Intake of sodium alginate and calcium may decrease the absorption of calcium.
Excessive vitamin A use has also been found to alter bone turnover. Too much preformed vitamin A can promote fractures. Avoid vitamin supplements that have large amounts of vitamin A as preformed vitamin A, unless prescribed by a doctor. Vitamin A in the form of beta-carotene does not appear to increase one's fracture risk.
Use of vitamin D and calcium increases the absorption of calcium. Vitamin D is important and recommended for optimal calcium absorption.