As vitamin A has many functions in the human body, itsdeficiency is associated with serious health problems. One of the earliest and the most specific manifestations of vitamin A deficiency is impaired vision, particularly in dim light, also known as night blindness. If the deficiency persists, further eye damage may occur, which can eventually result in total blindness. Other consequences of vitamin A deficiency include impaired immunityand various skin problems. Moreover, the right amounts of vitamin A are extremely important for pregnant and breastfeeding women to support normal child development. Excessive intake of vitamin D can only occur by taking dietary supplements. But one would have to take some 40,000 IU (1000 mcg) per day for several months to cause vitamin D overdose. x] Papadimitriou, Dimitrios T. “The Big Vitamin D Mistake.” Journal of preventive medicine and public health = Yebang Uihakhoe chi vol. 50,4 (2017): 278-281. doi:10.3961/jpmph.16.111 This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (). New FDA guidelines require that vitamin D be reported in µg. Manufacturers may also list the IU amount in parentheses following the amount in µg. In fact, 1 cup (70 g) of raw white mushrooms provides less than 1% of the DV for vitamin D. Meanwhile, the same amount of UV-exposed raw white mushrooms contains nearly 92% of the DV ( 35, 36).

There are numerous recommendations which make taking vitamin D unnecessarily complicated. But if you follow the above dosage and have your 25(OH)D tested after 3 months, you'll see how easy it can be to get your vitamin D levels into the optimal range. Known cases of vitamin D toxicity with hypercalcemia in which the 25(OH)D concentration and vitamin D dose are known all point to an intake of 40,000 IU (1,000 mcg) a day or more. Conversely, if the soft gel capsule was described as '150mcg of Vitamin A as retinol' and I wanted to convert to IU, I would divide it by 0.3. Older people also often spend more time indoors. This means they get less exposure to sunlight, which is the best way to naturally boost vitamin D levels.Vitamin D belongs to the family of fat-soluble vitamins, which include vitamins A, D, E, and K. These vitamins are absorbed well with fat and are stored in the liver and fatty tissues ( 6).

If you suffer from a disease that makes it absolutely necessary for your vitamin D level to be in the optimal range, or if you want to know your exact level, then you should have your vitamin D level measured. The blood test to measure your vitamin D levels is called the 25(OH)D blood test. Taking too many vitamin D supplements over a long period of time can cause too much calcium to build up in the body (hypercalcaemia). This can weaken the bones and damage the kidneys and the heart. Each ‘1-A-Day’ vitamin D supplement contains 10 micrograms (µg) of vitamin D. This is equivalent to 400 international units (IU) of vitamin D. This is the daily amount recommended for the general population by government for general health and in particular to protect bone and muscle health.Make sure you keep your vitamin D levels topped up with Holland & Barrett Vitamin D Supplements. Whether you prefer to take Vitamin D Tablets, Vitamin D Chewy Gummies, or use a Vitamin D Spray– we have you covered!

is the symbol for the metric measurement microgram, which is one thousandth of a milligram or one millionth of a gram. The letter µ is a greek letter, which means “small”, though often it “ug” or “mcg” (microgram) are used in its place due to typographical unavailability. Added translation and language selection for German (27%) and Dutch (16%). Thanks to all contributors! Since direct sunlight produces 10,000 IU (250 mcg) of vitamin D in the human body, this may be the physiological upper limit. International unit (IU)— In pharmacology, the international unit is a unit of measurement for the amount of a substance; the mass or volume that constitutes one international unit varies based on which substance is being measured, and the variance is based on the biological activity or effect, for the purpose of easier comparison across substances. International units are used to quantify vitamins, hormones, some medications, vaccines, blood products, and similar biologically active substances. Many biological agents exist in different forms or preparations (e.g. vitamin A in the form of retinol or beta-carotene). The goal of the IU is to be able to compare these, so that different forms or preparations with the same biological effect will contain the same number of IUs. To do so, the WHO Expert Committee on Biological Standardization provides a reference preparation of the agent, arbitrarily sets the number of IUs contained in that preparation, and specifies a biological procedure to compare other preparations of the same agent to the reference preparation. Since the number of IUs contained in a new substance is arbitrarily set, there is no equivalence between IU measurements of different biological agents. For instance, one IU of vitamin E cannot be equated with one IU of vitamin A in any way, including mass or efficacy. Despite its name, IU is not part of the International System of Units used in physics and chemistry. The IU should not be confused with the enzyme unit, also known as the international unit of enzyme activity and abbreviated as U. WikipediaThat’s because your body makes dietary vitamin D3 out of the cholesterol in the skin when it is exposed to the sun’s UV rays ( 1).