Vitamin D is a fat-soluble vitamin, which also acts as a hormone, that the body needs to maintain healthy structure and function. Unlike essential vitamins and minerals that must be consumed in food or supplements, vitamin D is non-essential, meaning the body can generally make enough of it to meet its demand.

Vitamin D could also be called “conditionally essential.” Under certain conditions, such as lack of sunlight exposure, the body might not make enough vitamin D. When that happens, an individual can become deficient in vitamin D, particularly if they aren’t consuming enough to make up for the production deficit.

Can you take too much vitamin D?

Although an individual might need to take a vitamin D supplement for a time if their vitamin D level is low, too much vitamin D can be toxic to the body and negatively affect health. Vitamin D toxicity is also called hypervitaminosis D.

When vitamin D level remains too high, a condition called hypercalcemia – too much calcium in the blood – can occur. This happens because vitamin D helps with calcium absorption in the gut. It also mobilizes calcium from the bones, helping to ensure there is adequate calcium in the blood when dietary intake of calcium is too low. Too much vitamin D can send this process into overdrive, pulling too much calcium from the bones and oversaturating the blood with it.

Symptoms of too much vitamin D

If you take too much vitamin D3, side effects might occur. These side effects – symptoms of vitamin D overdose or hypervitaminosis D – are most often due to resulting hypercalcemia and include decreased appetite, nausea and vomiting, constipation, dehydration, increased thirst, frequent urination, muscle weakness, and fatigue. Vitamin D toxicity usually resolves without serious complications so long as appropriate treatment steps are taken.

Although vitamin D toxicity is a serious health risk, a vitamin D deficiency is much more common. A low level of vitamin D can be due to one or more of the following:

  • Not enough sun exposure – e.g., living in northerly latitudes, regular use of sunscreen and sun-protective clothing, living/working mainly indoors
  • Having a darker skin tone – melanin in skin absorbs the UV rays that trigger vitamin D synthesis
  • A low-vitamin D diet – vegetarian, vegan, and other predominantly plant-based diets can be low in vitamin D sources
  • Difficulty absorbing vitamin D – certain medical conditions can interfere with dietary vitamin D absorption
  • Taking medications – some prescription medications can deplete vitamin D or inhibit its synthesis
  • Chronic liver or kidney disease – inhibits the conversion of vitamin D to its active form

Screening for vitamin D deficiency is usually only done when an individual has symptoms that might be related to such a deficiency. However, because vitamin D toxicity is a health risk, it is a good idea to check your vitamin D status before starting supplementation. If your doctor recommends a higher dose of vitamin D – usually 10,000 international units (IU) per day or greater – follow-up testing is necessary to ensure your vitamin D level is improving and toxicity does not occur.

How to get vitamin D

Amazingly, the human body is equipped to make vitamin D from sunlight. Although it sounds simple enough, there are quite a few steps and several organ systems involved in this process. Let’s take a brief look at how the process works:

When skin is exposed to UVB rays from sunlight, it triggers a chemical reaction with a certain type of cholesterol (7-dehydrocholestrol or 7-DHC) that resides in large quantities in the outermost layer of skin – the epidermis. This reaction forms a precursor called pre-D3. As sun exposure continues to warm the skin, the heat that is created accelerates the conversion of pre-D3 to vitamin D3 (cholecalciferol).

Vitamin D3 must undergo further conversion to reach its active form – the form used by the body – including conversion by the liver to its most abundant form in the blood, 25-OHD3 or calcifediol. From the liver, calcifediol moves to the kidneys where it becomes calcitriol, the active form.

Although you can take too much vitamin D from supplements, your body won’t make too much from sun exposure alone.

What foods have vitamin D?

Aside from getting sun exposure for your body to make vitamin D, you can also eat vitamin D-rich foods. However, vitamin D sources from food are somewhat limited. Animal sources provide vitamin D3, the more potent form, with the best vitamin D sources being fatty fish such as trout, salmon, tuna, mackerel, and sardines. Algae is a vegan source of vitamin D3.

Beef, chicken, and cheese provide smaller amounts of vitamin D3 per serving, and mushrooms are a plant-based source of vitamin D2, which is less potent than vitamin D3 but can also be converted to the active form of vitamin D in the body. Other vitamin D-rich foods include milk (both dairy and plant-based), orange juice, and cereals, all of which are usually fortified with vitamin D2 and/or D3 (be sure to check the product label).

What about additional sources beyond foods rich in vitamin D? 

Vitamin D is available as vitamin D2 or vitamin D3 in over-the-counter nutritional supplements, usually as gummies, capsules, tablets, or liquid. Vitamin D is also often found in multivitamins and other supplements that support bone health, immune function, men’s or women’s health, muscle and joint function, cardiovascular health, the brain and nervous system, and metabolic health.* Cod liver oil is another common supplemental source of vitamin D.

Vitamin D3 supplements vary in strengths ranging from 400 IU per capsule to 50,000 IU per capsule. It’s always a good idea to check the label of any supplements you are taking for vitamin D. Multiple sources of vitamin D can add up and, when taken regularly, could become a risk for vitamin D toxicity.

Some individuals, particularly those with certain medical conditions, might need a prescription for a higher strength vitamin D than is available over the counter. High-dose vitamin D should be monitored by the prescribing physician to ensure vitamin D toxicity does not occur.

If you were wondering, “can you take too much vitamin D?” before reading this article, then you might now be curious how much vitamin D is too much. For most people, a combination of food and supplementation with up to 10,000 IU of vitamin D daily is unlikely to cause toxicity. Research shows that hypercalcemia is most often seen in individuals taking amounts greater than 50,000 IU of vitamin D daily. And most of us do not need that much supplemental vitamin D. For individuals who do require more vitamin D, supplementing with amounts higher than 10,000 IU daily should be closely monitored by a health-care practitioner.

Thorne offers a variety of vitamin D3 supplements and formulas for supporting individual health goals:

Now that you know the answer to “can you take too much vitamin D?” you might be wondering what your vitamin D level is. Check out Thorne’s at-home Vitamin D test. This convenient, at-home test kit measures total vitamin D in the blood and provides personalized recommendations for optimizing your vitamin D level based on your individual results.