Abnormally elevated blood calcium ('hypercalcemia') has been reported only with the consumption of large quantities of calcium supplements (1.5 to 16.5 g/day), usually in combination with calcium carbonate ('antacids') and milk to treat open, painful wounds in the stomach ('peptic ulcers') (57). Mild hypercalcemia may be without symptoms or may result in loss of appetite, nausea, and vomiting, while more severe hypercalcemia may result in confusion, delirium, coma, and if not treated, death. Since the treatment for peptic ulcers has changed, the incidence of this syndrome has decreased considerably (2).

Although the risk of forming kidney stones is increased in individuals with abnormally elevated urinary calcium, this condition is not usually related to calcium intake, but rather to increased excretion of calcium by the kidneys (50).

Calcium and prostate cancer risk

Epidemiological studies have raised concern that high calcium intakes are associated with increased risk of prostate cancer:

A large prospective cohort study in the U.S. followed more than 50,000 male health professionals for eight years and found that men whose calcium intake was 2,000 mg/day or more had a risk of developing advanced prostate cancer that was three times higher than men whose calcium intake was less than 500 mg/day and a risk of developing spreading ('metastasized') prostate cancer that was more than four times greater (51). Similar results were observed in a case-control study in Sweden (52).

Neither study found calcium intake to be associated with an increased risk of total prostate cancer or non-advanced prostate cancer.

More recently, a prospective study in a group of 29,133 male smokers, followed for 17 years, found that high calcium consumption (more than 1,000 mg/day) was associated with an increased risk of prostate cancer (53).

The physiologic mechanisms underlying the relationship between calcium intake and prostate cancer are not yet clear.

Not all epidemiological studies have demonstrated an association between calcium intake and prostate cancer: one review reported that (only) seven out of 14 case-control studies and five out of nine prospective cohort studies found statistically significant positive associations between prostate cancer and some measure of dairy product consumption (e.g., calcium intake) (54).

Until the relationship between calcium and prostate cancer is clarified, it is reasonable for men to consume the recommended adequate intake level of a total of 1,000 to 1,200 mg/day calcium (2).

Tolerable upper intake level

The European Food Safety Authority has established a tolerable upper intake level (UL) for calcium intake only for adults: 2,500 mg/day (39). This UL applies also to pregnant and breast-feeding women. Scientific data have been considered insufficient to derive an UL for children and adolescents.

In 2010, the U.S. Institute of Medicine has set a tolerable upper level (UL) of intake for calcium (56):


 Age Group

UL (mg/day) 
 Infants 0–6 months1,000 
 Infants 6–12 months1,500 
 Children 1–8 years2,500 
 Children 9–13 years3,000 
 Adolescents 14–18 years3,000 
 Adults 19 – 50 years2,500 
 Adults 51 and older2,000 
 14 – 18 years old
 pregnant/lactating women
 19 – 50 years old 
 pregnant/lactating women

Drug interactions

Please note: 
Because of the potential for interactions, dietary supplements should not be taken with medication without first talking to an experienced healthcare provider.

Calcium-mineral interactions

The presence of calcium decreases iron absorption from most supplements and food sources other than meat. However, calcium supplementation up to 12 weeks has not been found to change iron nutritional status, probably due to a compensatory increase in iron absorption. Individuals taking iron supplements should take them two hours apart from calcium-rich foods or supplements to maximize iron absorption.

Although a number of studies did not find high calcium intakes to affect zinc absorption or zinc nutritional status, a study in ten men and women indicated that 600 mg of calcium consumed with a meal decreased the absorption of zinc from that meal by 50% (55).

Authored by Dr Peter Engel in 2010, reviewed and updated by Dr Igor Bendik-Falconnier on 16.10.17