Recommended intake for adults, in milligrams per day (recommended calcium allowances based on North American and western European data):

• Adolescents, 10–18 years - 1300 mg / day
• Females, 19 years to menopause - 1000 mg / day
• Females, pregnant women (last trimester) - 1200 mg / day
• Females, lactating women - 1000 mg / day
• Females, postmenopause - 1300 mg / day
• Males, 19–65 years - 1000 mg / day
• Males, 65+ years - 1300 mg / day

The calcium requirement of an adult is generally recognized to be the intake required to maintain calcium balance and therefore skeletal integrity. 

Calcium balance is determined by the relationship between calcium intake and calcium absorption and excretion. Relatively small changes in calcium absorption and excretion can neutralize a high intake or compensate for a low one. 

A positive calcium balance (net calcium retention) is required throughout growth, particularly during the first 2 years of life and during puberty and adolescence. These age groups therefore constitute populations at risk for calcium deficiency, as do pregnant women (especially in the last trimester), lactating women, postmenopausal women, and, possibly, elderly men.