Charliehorse like cramps in upper abdomen due to low calcium. How to prevent this?

Difficult to say. Low calcium in the blood is rare unless you have serious organ illnesses. Ask your doctor for guidance about the amount of water you should drink daily with the pills prescribed. Low calcium diet causes your body to take it from your bones and teeth, and this does not affect the blood calcium. Magnesium usually counteracts gut spasms and prevents cramps from constipation. Be well.