However, doses up to 10,000 IU have not been shown to cause toxicity in healthy individuals ( 11, 16). Since relatively little is known about how vitamin D toxicity works, it’s hard to define an exact threshold for safe or toxic vitamin D intake ( 5).Īccording to the National Academy of Medicine, formerly known as the Institute of Medicine, 4,000 IU is the safe upper level of daily vitamin D intake. The safe upper limit is considered to be about 60 ng/mL, but people with symptoms of toxicity usually have levels above 150 ng/mL. Summaryīlood levels in the range of 20–30 ng/mL are usually considered sufficient. Safe upper limit: 60 ng/mL, or 150 nmol/LĪ daily vitamin D intake of 1,000–4,000 IU (25–100 mcg) should be enough to ensure optimal blood levels for most people.Guidelines for blood levels of vitamin D are as follows ( 10, 11, 12, 13, 14, 15): Vitamin D is very important for bone health and has also been linked with immune function and protection against cancer ( 8, 9). The main dietary sources of vitamin D are fish liver oils and fatty fish ( 7).įor people who don’t get enough sunlight, vitamin D supplements are important.
#Mcg to iu vitamin d skin
It’s produced in the skin when it’s exposed to sun. Vitamin D is an essential vitamin, and almost every cell in your body has a receptor for it ( 6). It implies that vitamin D levels in the body are so high that they cause harm, leading to hypercalcemia and other symptoms.īlood levels of vitamin D: Optimal vs. Vitamin D toxicity is also termed hypervitaminosis D. High calcium levels can cause various symptoms, and the calcium can also bind to other tissues and damage them. One of the main signaling processes has to do with increasing the absorption of calcium from the digestive system ( 3).Īs a result, the main symptom of vitamin D toxicity is hypercalcemia, or elevated levels of calcium in the blood ( 4, 5).
This may lead to elevated levels of “free” vitamin D in the body, which may travel inside cells and overwhelm the signaling processes affected by vitamin D.
However, when vitamin D intake is extreme, the levels can become so high that there isn’t any room left on the receptors or carrier proteins. Very little “free” vitamin D is available ( 1, 2). Usually, most of the body’s vitamin D is in storage, bound to either vitamin D receptors or carrier proteins. It travels inside cells, telling them to turn genes on or off. However, we know that the active form of vitamin D functions in a similar way as a steroid hormone. The exact mechanism behind vitamin D toxicity is complicated and isn’t fully understood at this point. In contrast to water-soluble vitamins, the body has no easy way of getting rid of fat-soluble vitamins.įor this reason, excessive amounts may build up inside the body. Vitamin D toxicity implies that vitamin D levels in the body are so high that they cause harm.