According to the Mayo Clinic, exceeding the recommended dosage of vitamin C could cause: 

• nausea;
• vomiting;
• diarrhea;
• abdominal bloating and cramps;
• heartburn;
• headache;
• kidney stones; and
• insomnia. 

And that's not all. Too much vitamin C may cause the body to absorb too much iron – a condition that can lead to serious health problems. Researchers have found that excess vitamin C could interfere with the absorption and metabolism of vitamin B12, which is another essential nutrient. 

With a doctor's guidance, limit vitamin C supplement intake if you take the following medications -- adverse side effects have been reported: 

• acetaminophen;
• aluminum-based antacids;
• aspirin; and
• Warfarin. 

A doctor can advise how to modify vitamin C intake, taking medications and diet into consideration.