Overdosage of centain vitamins may causes some side effects. Therefore, the supplementation of vitamins should be safely dosed with the guides of a reliable medical instruction. Excessive intake of vitamin A can be harmful to bones and skin, causing weakness and brittleness. Large doses of niacin can cause liver damage, peptic ulcers, and skin rashes. Vitamin B6 toxicity can damage sensory nerves. High doses of PABA can cause blood sugar to drop. There is a high health risk associated with consuming too much vitamin D.