Do vitamin D supplements have any side effects?

Vitamin D supplement side effects include skin rash, irritation and inflammation; calcium build-up in the arteries, daytime sleepiness, headaches, and increased risk of heart attack or stroke. Constipation, cramps, diarrhea, and increased risk of kidney or urinary stones are also vitamin D supplement side effects, according to the Mayo Clinic.

People with low blood sugar or diabetes may need a health care professional to monitor their vitamin D supplement intake; the supplement may affect their blood sugar levels. Vitamin D supplements can also impact blood pressure. Pregnant and breastfeeding women, people with blood pressure disorders, and those taking herbs or drugs affecting blood pressure should be careful when taking vitamin D, suggests the Mayo Clinic.