Vitamin D is essential, but it is also one of the few vitamins you can take too much of. Toxicity is rare, and it almost always comes from high-dose supplements rather than sunshine or food. Here is what vitamin D toxicity is, the symptoms to know, the doses involved and how to supplement safely.
What is vitamin D toxicity?
Vitamin D toxicity, also called hypervitaminosis D, happens when vitamin D builds up to the point that your body absorbs too much calcium from food, raising the calcium in your blood (hypercalcemia). In healthy people it is usually caused by months of very high-dose supplements, not by sun exposure or a normal diet: your skin regulates how much vitamin D it makes, and very few foods contain much of it.
Vitamin D works by helping your body absorb calcium and phosphorus, which is why it matters for bones; our guide to what vitamin D does covers its other roles. The same mechanism is what causes trouble when there is far too much of it.
What are the symptoms of too much vitamin D?
Most symptoms come from high blood calcium. The ones doctors see most often are confusion, apathy, repeated vomiting, abdominal pain, excessive thirst and urination, and dehydration. High blood calcium can also cause nausea, constipation, poor appetite, weakness, weight loss, kidney stones and kidney damage, and calcium deposits in soft tissues such as the heart and lungs.
If you take a high-dose vitamin D supplement and notice any of these, stop taking it and see a doctor, who can check your blood calcium and vitamin D levels.
How much vitamin D is too much?
The upper limit, the most you can take daily over the long term without expecting harm, is 4,000 IU (100 mcg) a day for adults and children 9 and older, and lower for younger children: 1,000 IU for babies up to 6 months, 1,500 IU from 7 to 12 months, 2,500 IU from 1 to 3 years and 3,000 IU from 4 to 8 years.
Going over that limit now and then is not the same as toxicity. A clinical review puts the threshold for acute toxicity at probably more than 10,000 IU a day, enough to push blood levels above 150 ng/mL (375 nmol/L), and notes that taking more than 4,000 IU a day for years may carry risks of its own. On a blood test, levels above 50 ng/mL (125 nmol/L) are probably too high.
Some people react to much smaller amounts. Granulomatous conditions such as sarcoidosis, and some lymphomas, make the body produce extra active vitamin D, and a few people are hypersensitive to it, so doses that are normally safe can raise their calcium. If you have one of these conditions, take vitamin D only on your doctor's advice.
How much vitamin D do you actually need?
Far less than the toxic range. The RDA is 600 IU (15 mcg) a day for ages 1 to 70 and 800 IU (20 mcg) after 70. Your needs depend on age, skin tone, body weight, where you live and how much sun you get; our article on how much vitamin D you need explains each factor. If you think you are low, the signs of deficiency and a blood test are a better guide than guessing at a higher dose.
How do you take vitamin D safely?
- Add up every source. A multivitamin, a separate vitamin D supplement and fortified foods can stack up.
- Know the upper limit. For adults it is 4,000 IU a day from all sources combined; follow the label of any supplement you take.
- Retest on a high dose. If your doctor puts you on a treatment dose, ask when to recheck your levels.
- Check your medicines. Some medicines, including certain statins, steroids and weight-loss drugs, affect vitamin D levels, so tell your doctor what you take.
Our Sol Food tablets provide 2,000 IU of vitamin D3 from lichen, and Sol Food High Potency provides 5,000 IU of D3 with MenaQ-7 vitamin K2. Take either with a meal that contains some fat; we cover timing in when to take vitamin D. If you are pregnant, have kidney disease or take prescription medicines, check with your doctor first.
