Calcium ascorbate combines calcium and vitamin C in one supplement, with each 1,000-milligram supplement providing approximately 900 milligrams of vitamin C and 100 milligrams of calcium. The calcium makes the vitamin C less acidic, so it may be less likely to cause gastrointestinal side effects than other types of vitamin C supplements. However, this doesn't mean these supplements are free from potential side effects, so speak with your doctor to make sure you can safely take calcium ascorbate.
Minor Side Effects
Although not everyone experiences side effects with vitamin C or calcium supplements, these can occur, especially at high doses. Supplemental vitamin C sometimes causes headache, heartburn, nausea, stomach cramps, vomiting, gas or diarrhea. If you have diabetes, high doses of vitamin C may cause your blood sugar to go up. Calcium can also cause bloating, gas, constipation and acid rebound in some people. Reducing the amount of calcium ascorbate you take per day may lessen or eliminate any side effects you experience.
Potential Medication Interactions
Vitamin C supplements can interact with statins, protease inhibitors, chemotherapy, blood thinners, niacin, estrogens, aluminum from antacids, fluphenazine, acetaminophen and aspirin, potentially making these medications less effective or increasing the risk for side effects. Calcium can also interact ceftriaxone, certain types of antibiotics, diuretics, thyroid medications and certain heart medications.
Getting more than 2,000 milligrams of vitamin C can cause diarrhea and increase your risk for kidney stones. Don't get more than the tolerable upper intake level for calcium of 2,500 milligrams per day. Excessive calcium can cause you to absorb less zinc and iron and may also cause kidney problems, constipation and calcification of your organs.
People with blood-iron disorders, kidney stones, cancer and sickle cell disease should avoid taking vitamin C supplements, which might make these conditions worse, according to MedlinePlus. The calcium from calcium ascorbate isn't as easily absorbed as that from calcium citrate, but you can improve the absorption if you take your supplement with food.