Everyone needs vitamin D. But many people are deficient in this essential nutrient — up to 35 percent of people in the U.S., per the Cleveland Clinic — and may experience vitamin D deficiency symptoms like weakness and fatigue.
Just how much vitamin D you need per day, though, depends on many different factors.
Video of the Day
Here, learn about the recommended daily amount, plus the potential benefits and side effects of taking vitamin D supplements.
What Is Vitamin D?
Vitamin D is a hormone naturally produced in the body. You need it for a healthy immune system and strong bones, and it also helps your body absorb other essential nutrients like calcium and phosphorus, per the Harvard T.H. Chan School of Public Health.
There are two forms of vitamin D, according to the Linus Pauling Insitute:
- Vitamin D3, aka cholecalciferol, is the form naturally found in our bodies. Vitamin D and D3 are often used interchangeably because this is the form best utilized by our bodies. For this reason, most vitamin D supplements contain vitamin D3.
- Vitamin D2, or ergocalciferol, is found in some plant foods, such as mushrooms. It's also sometimes found in foods fortified with vitamin D.
Sources of Vitamin D
The main source of vitamin D is exposure to sunlight. When your skin is exposed to ultraviolet-B (UVB) radiation from the sun, your body makes vitamin D3.
Vitamin D is also found in certain foods. Some foods rich in vitamin D3 include the following, per the Harvard T.H. Chan School of Public Health:
- Cod liver oil
- Egg yolks
- Beef liver
- Some mushrooms
- Fortified cereals
- Fortified milks
And if you're vitamin D deficient — which your doctor can determine through blood tests — you might consider taking vitamin D supplements.
Signs of Low Vitamin D
If you have low vitamin D3 levels, you may experience the following symptoms, per the Cleveland Clinic:
- Bone and joint pain (especially in your back)
- Muscle weakness, aches or cramps
- Mood changes like depression
Some people don't have any symptoms at all, though.
Several things can put you at higher risk for vitamin D deficiency, according to the Cleveland Clinic and Johns Hopkins Medicine, including:
- Not getting enough vitamin D through sunlight or in your diet. Older adults and people who live in more northern climates are especially at risk because they tend to spend less time outdoors
- Having darker skin
- Weight-loss surgery
- Having certain medical conditions, such as celiac disease, Crohn's disease, cystic fibrosis, kidney disease, liver disease or obesity
- Taking certain medications, such as cholesterol-lowering drugs, laxatives, Orlistat (an anti-obesity drug), Rifampin (to treat tuberculosis) and steroids
How Much Vitamin D3 per Day Do You Need?
The amount of vitamin D you need will depend on your age, sex, the amount of sun exposure you get and your ethnicity. One place to start is with the recommended dietary allowance (or RDA).
The RDA describes an amount sufficient for the needs of 97 to 98 percent of healthy people. For both men and women, the RDA for vitamin D is as follows, per the National Institutes of Health (NIH):
- Ages 1 to 70 (including people who are pregnant or lactating): 600 International Units (IU)
- Older than 70: 800 IU
The RDA for vitamin D was raised in 2010 based on a number of research studies indicating that previous standards were too low, according to an April 2012 review in Dermato-Endocrinology.
How Much Vitamin D Can You Take per Day?
Vitamin D is a fat-soluble vitamin, which means it can build up in the body, and too much can cause toxicity (more on that below). The highest dose of vitamin D you can take without causing toxicity is called the tolerable upper limit. The tolerable upper limit is the same for men and women (ages 9 and older): 4,000 IU daily, according to the NIH.
You cannot get too much D3 from the sun, and dietary intake also is unlikely to result in too much D3.
You can overdose on D3 supplements, though, according to the Linus Pauling Institute, which is why you should always talk to your doctor about whether you need a supplement and what the correct dosage is for you.
Symptoms of vitamin D toxicity include the following, per the Cleveland Clinic:
- Decrease in appetite
- Nausea and vomiting
- Increased thirst
- Frequent urination
- Confusion, lethargy and fatigue
- Muscle weakness and difficulty walking
- Bone pain
- Kidney stones
Risks of Too Much Vitamin D3
Taking too much vitamin D3 (and vitamin D in general) can have significant risks. Because vitamin D assists in calcium absorption from the intestine, very high vitamin D levels can cause high calcium levels as well.
Symptoms of high calcium levels include excessive thirst, frequent urination, bone loss and pain, kidney stones and heart irregularities, per the Mayo Clinic. In fact, some kidney stones are primarily made up of calcium, per the National Kidney Foundation.
Other vitamin D3 side effects (if you're taking too much) including the following, per the Mayo Clinic:
- Nausea and vomiting
- Poor appetite and weight loss
- Confusion and disorientation
- Heart rhythm problems
- Kidney stones and kidney damage
This is why it's important to pay attention to vitamin D3 dosage instructions on supplement labels and ask your doctor about the right amount for you.
Benefits of Vitamin D3
We know that vitamin D is important for us, but what does vitamin D3 do, exactly?
Here's a look at the research-backed benefits:
1. It Might Help Manage or Prevent Osteoporosis
Of the 44 million Americans who have or are at risk for developing osteoporosis, 68 percent are women, per the National Osteoporosis Foundation.
Vitamin D in any form alone doesn't appear to lower the risk of developing fractures or of reducing falls, according to the National Institutes of Health (NIH).
But taking both vitamin D and calcium together is associated with higher bone density, and can help people with deficiencies in both nutrients, per an April 2020 study in Nutrients.
2. It May Be Beneficial During Pregnancy
Vitamin D supplementation in pregnant people with low vitamin D may improve fetal growth and reduce the risks for slow growth, preeclampsia, preterm birth and gestational diabetes, according to an October 2020 review in Current Opinion in Gynecology and Obstetrics.
3. It May Help Hypertension
Hypertension, or high blood pressure, is commonly seen in people with a vitamin D deficiency.
But some studies have shown that vitamin D3 supplementation is able to lower blood pressure in those with hypertension.
One small May 2019 review in Medicine found that taking vitamin D3 was associated with significantly reduced systolic blood pressure in people over age 50 and those with obesity.
Can It Reduce Breast Cancer Risk?
While some people might think that taking vitamin D can help reduce breast cancer risk, researchers haven't found enough data to show a sufficient correlation. Further research is needed to determine that vitamin D reduces breast cancer risk, per a March 2005 review in Cancer Causes and Control.
Does It Lower the Risk of Colorectal Cancer?
Low vitamin D levels were associated with a 31 percent higher colorectal cancer risk in a February 2019 study in the Journal of the National Cancer Institute that followed more than 5,000 people with colorectal cancer.
However, this study only showed a correlation between D deficiency and colorectal cancer. More research needs to be done to determine whether low vitamin D contributes to colorectal cancer development and/or if supplementation can help reduce the risk.
When to See a Doctor
Before you start taking a vitamin D supplement, talk to your doctor to see if you need it.
If you notice fatigue, muscle weakness and cramps or changes in your mood, it's worth visiting the doctor to get a blood test to check your vitamin levels.
Your doctor can determine if you are vitamin D deficient — or are taking too much vitamin D — and can recommend the proper dosage, if needed.
1. What's the Difference Between Vitamin D and Vitamin D3?
Vitamin D is the hormone our bodies produce after exposure to sunlight or after eating vitamin D-rich foods. Vitamin D3 is simply a form of D that is sold in supplement form. It most closely resembles the type that all animals, including humans, naturally produce.
Another form of vitamin D sold in supplement form is vitamin D2. This is the plant form of the nutrient.
Both D2 and D3 can help correct a vitamin D deficiency, but most doctors recommend D3 because it is slightly more active and effective, per Columbia University's Irving Medical Center.
2. When Should I Take Vitamin D: Morning or Night?
It does not really matter whether you take vitamin D in the morning or at night. The only thing that may help improve its effectiveness is if you take it with food.
Vitamin D is a fat-soluble vitamin, meaning that it best absorbs into your body if taken with meals that have a source of healthy fats. Even taking it with your bedtime snack of yogurt with fruit, or at breakfast with your scrambled eggs will do, per the Cleveland Clinic.
You can also try taking your vitamin D and B, C or multivitamins together, whether part of your morning or night routine.
3. Is 2,000 IU of Vitamin D Safe?
One thousand to 2,000 IU of vitamin D per day is generally considered safe and should help people achieve adequate blood levels of vitamin D, per the Mayo Clinic.
However, the RDA for vitamin D is anywhere from 600 to 800 IU. Your doctor can recommend the amount you need based on your current vitamin D levels, any underlying conditions you have or other health concerns you wish to address.
- Linus Pauling Institute: Vitamin D
- Cancer Causes and Control:"The Epidemiology of Vitamin D and Cancer Incidence and Mortality"
- Johns Hopkins Medicine: "How Does Vitamin D Affect Women’s Health?"
- Current Opinion in Gynecology and Obstetrics: "Vitamin D supplementation during pregnancy: an overview"
- Journal of the National Cancer Institute: "Circulating Vitamin D and Colorectal Cancer Risk: An International Pooling Project of 17 Cohorts"
- National Osteoporosis Foundation: "Osteoporosis Fast Facts"
- NIH: "Vitamin D"
- Nutrients: "Calcium and/or Vitamin D Supplementation for the Prevention of Fragility Fractures: Who Needs It?"
- Harvard T.H. Chan School of Public Health: "Vitamin D"
- Mayo Clinic: "Hypercalcemia"
- National Kidney Foundation: "Calcium Oxalate Stones"
- Columbia University's Irving Medical Center: "What's the Deal with Vitamin D?"
- Cleveland Clinic: "The Best Time to Take Vitamins"
- Mayo Clinic: "Mayo Clinic Q and A: How much vitamin D do I need?"
- National Institutes of Health: "Vitamin D"
- Dermato-Endocrinology: "Evidence-based D-bate on health benefits of vitamin D revisited Michael F. Holickcorresponding author"
- Cleveland Clinic: "Vitamin D Toxicity (Hypervitaminosis D)"
- Medicine: "The effect of vitamin D3 on blood pressure in people with vitamin D deficiency"
- eMedTV: Osteoporosis