Possible side effects of cholecalciferol or vitamin D-3 supplements are nausea, constipation, loss of appetite, increased thirst and unusual tiredness, explains WebMD. Side effects don't usually occur when vitamin D supplements are taken in normal doses, but taking too much vitamin D can lead to dangerously high calcium levels.
In very rare cases, people may experience allergic reactions to cholecalciferol supplements, states WebMD. Signs of an allergic reaction include rash, itching, swelling of the face or throat, severe dizziness, and difficulty breathing. Individuals who think they may be having an allergic reaction to cholecalciferol supplements should seek immediate medical care. Symptoms of a cholecalciferol overdose include seizures, confusion and irregular heartbeat. Those who think that they or a loved one may be suffering from an overdose of cholecalciferol should contact an emergency room or poison control center.
To avoid side effects and negative interactions, people with a history of high calcium or vitamin D levels and those who have kidney or liver disease should contact their doctors before beginning to take cholecalciferol supplements, advises WebMD. These supplements are best absorbed when taken with food. Individuals are advised only to take cholecalciferol supplements as directed on the label or as instructed by the doctor who prescribed them. Chewable cholecalciferol tablets should never be swallowed whole, and liquid supplements should be measured carefully to ensure proper dosing.