Hypervitaminosis is a condition of abnormally high storage levels of vitamins, which can lead to various symptoms as over excitement, irritability, or even toxicity. Specific medical names of the different conditions are derived from the given vitamin involved: an excess of vitamin A, for example, is called hypervitaminosis A. Hypervitaminoses are primarily caused by fat-soluble vitamins (D and A), as these are stored by the body for longer than the water-soluble vitamins. Generally, toxic levels of vitamins stem from high supplement intake and not always from natural sources but rather the mix of natural, derived vitamins and enhancers (vitamin boosters). Toxicities of fat-soluble vitamins can also be caused by a large intake of highly fortified foods, but natural food in modest levels rarely deliver extreme or dangerous levels of fat-soluble vitamins. The Dietary Reference Intake recommendations from the United States Department of Agriculture define a "tolerable upper intake level" for most vitamins. For those who are entirely healthy and do not experience long periods of avitaminosis, vitamin overdose can be avoided by not taking more than the normal or recommended amount of multi-vitamin supplement shown on the bottle and not ingesting multiple vitamin-containing supplements concurrently. Signs and symptoms A few described symptoms: Frequent urination and/or cloudy urine Increased urine amount Eye irritation and/or increased sensitivity to light Irregular and/or rapid heartbeat Bone and joint pain (associated with avitaminosis) Muscle pain Confusion and mood changes ( e.g. irritability, inability to focus) Convulsions Fatigue Headache Flushing of skin (associated with niacin (vitamin B3) overdose) Skin disturbances (e.g. dryness, itching, cracking of skin, rashes, increased sensitivity to sun) Changes of hair texture (e.g. thickening and/or clumping of hair) Appetite loss Constipation (associated with iron or calcium overdose) Nausea and vomiting Diarrhoea Moderate weight loss (more commonly seen in long-term overdose cases) Causes With few exceptions, like some vitamins from B-complex, hypervitaminosis usually occurs with the fat-soluble vitamins A and D, which are stored, respectively, in the liver and fatty tissues of the body. These vitamins build up and remain for a longer time in the body than water-soluble vitamins. Conditions include: Hypervitaminosis A Hypervitaminosis D Vitamin B3 § Toxicity Megavitamin-B6 syndrome Prevention Prevention in healthy individuals not having any periods of avitaminosis or vitamin (vegetables) lack for 2 years at least is by not taking more than the expected normal or recommended amount of vitamin supplements. Epidemiology In the United States, overdose exposure