Vitamin A can cause severe or chronic poisoning, and even death. Taking vitamin B12 in large quantities can cause nausea, dizziness, restlessness, etc.
Vitamin C can occasionally cause diarrhea, red skin, headache, frequent urination, nausea and vomiting, stomach cramps and other reactions. Vitamin D is easy to poison, can cause hypercalcemia, in addition to headache, anorexia, drowsiness and other symptoms. Vitamin E is relatively non-toxic, and because it has anti-aging and other effects, many people take it as a long-term nutritional supplement.