Hypervitaminosis Toxicity due to an excessive intake of VITAMINS, especially overdosing with fatsoluble vitamins. Fat-soluble vitamins are not readily excreted and thus accumulate in fatty tissue. In contrast, the water-soluble vitamins are excreted by the kidney and, with the exception of VITAMIN B12, are not stored. Chronic high levels of VITAMIN A (e.g., 25,000 retinol equivalents or more per day) are linked to birth defects. Recent studies indicate that even 10,000 IU or 3,000 retinol equivalents per day are linked to an increased risk of birth defects. The consumption of 50,000 retinol equivalents for several months can cause toxic symptoms in adults such as headache, fatigue, nausea, hair loss, and blurred vision. Liver damage is possible. Symptoms disappear when vitamin A intake is restricted. VITAMIN D excess (25,000 to 250,000 IU daily for several months) can cause kidney stones, kidney failure, and heart irregularities. Excessive VITAMIN K can also be toxic. Symptoms include liver damage and JAUNDICE. VITAMIN E appears to be the safest of the fat-soluble vitamins.