While most bird keepers are aware of the repercussions of a calcium-deficient diet, many are uninformed of the dangers of too much calcium. Excess calcium from supplements, fortified foods and high-calcium diets, can cause the "milk alkali syndrome,"
which has serious toxicity and can be fatal. Excessive calcium intake can lead to hypercalcaemia (an elevated calcium level in the blood), complications of which include vomiting, abdominal pain and altered mental status.
- High calcium intakes can lead to constipation, an increased chance for developing calcium kidney stones, and may inhibit the absorption of iron and zinc from food.
- Too much calcium can cause the shell glands in the uterus to over-produce calcium, sometimes making the shells to adhere to the uterus, making it difficult (if not impossible ) for the hen to lay the egg.