Vitamin D is essential for good health and is normally produced within the body when the sun hits the skin. It is fat-soluble, and you can get it through foods and supplements. Vitamin D is needed for bone health and proper functioning of the immune system. Even though it is made naturally by the skin, vitamin D deficiency is common. You can take vitamin D supplements if your body is deficient of Vitamin D. About 42% of the adult population in the US has low Vitamin D levels. Nutritionists are commonly asked, “how much Vitamin D should I take?”

The answer depends on your age, sex, and whether you have Vitamin D deficiency. However, it is vital to first know the recommended Vitamin D daily intake. The purpose of this article is to highlight Vitamin D benefits, Vitamin D supplements, and answer the question “how much Vitamin D should I take?”

Vitamin D Supplements

Vitamin D functions like a steroid hormone in the body. There are two main forms of the vitamin - vitamin D2 and vitamin D3. Vitamin D2 is found in some mushrooms while vitamin D3 is found in egg yolks, fish liver oil, and oily fish. Vitamin D3 is more powerful than vitamin D2 and raises blood levels of vitamin D almost twice as much as vitamin D2.

Vitamin D is naturally made in the skin when it is exposed to sunlight’s UV-rays. Excess vitamin D is stored in body fat for later use. Each body cell has vitamin D receptors, and the vitamin is involved in many processes such as the protection against cancer, immune system function, and bone health. If your body is vitamin D deficient, you may need supplements, which are also vital for people with obesity.

Vitamin D Deficiency

a baby laying on the bed

It is a common problem worldwide. However, it is common in infants, young women, the elderly, and individuals who have dark skin. Approximately 42% of the US population has vitamin D deficiency, but this rate rises to 82% in Blacks and 70% in Hispanics. Occasional sun exposure is enough to fulfill your daily vitamin D requirements.

However, if you don’t have access to strong sunlight all year, for example people who live far south or north of the equator, your vitamin D levels may go down due to inadequate sunlight. Therefore, you need to rely on your diet or supplements for vitamin D.
Among adults, vitamin D deficiency is linked to:

  • Muscle weakness
  • Bone loss
  • Increased risk of fractures
the difference between normal anatomy and rickets

Among children, a severe vitamin D deficiency can cause growth delays and rickets (a disease where the bones become soft and become bow-shaped). Vitamin D deficiency has also been linked to type 1 diabetes, several cancers, thyroid issues, high blood pressure, and multiple sclerosis. For adults, if your body doesn’t get enough vitamin D, you are at risk of developing bone abnormalities, including fragile bones (osteoporosis) and osteomalacia (soft bones).

Symptoms of vitamin D deficiency among adults include:

  • Stress fractures in your hips, pelvis, and legs
  • Aches, tiredness, pains, and not feeling well in general
  • Severe muscle and bone pain or weakness; you may find it difficult to climb stairs or get up from the floor or a low chair

Factors that affect your ability to get adequate amounts of vitamin D include:

  • Using sunscreen
  • Spending a lot of time indoors
  • Living in big cities where buildings block sunlight
  • Living in an area with high pollution
  • Having darker skin (higher melanin levels limits vitamin D absorption)

Benefits of Vitamin D

The following are the benefits of Vitamin D:

Protects from Diseases

Vitamin D plays a role in:

  • Decreasing your likelihood of developing heart diseases and hypertension
  • Reducing the likelihood of developing type 2 diabetes
  • Reducing your risk of developing multiple sclerosis
  • Reduces your chance of developing flu
  • Reduces the risk of autism, Alzheimer's disease, rheumatoid arthritis, and asthma

Reduces Depression

a man having a head ache

Studies have established that vitamin D plays a vital role in regulating mood and reducing depression. In fact, some studies have revealed that people with depression who took vitamin D supplements noticed an improvement in the depression symptoms. In another study that involved individuals with fibromyalgia, researchers established that vitamin D deficiency was associated with depression and anxiety.

Boosts Weight Loss

We recommend adding vitamin D supplements to your diet if you are trying to prevent heart disease or lose weight. In one study, researchers established that individuals who took calcium and vitamin D supplements daily lost more weight than those in the control group, who took a placebo supplement. In the study, it was also revealed that the extra vitamin D and calcium intake suppressed appetite.

Prevents Cancer

Vitamin D is important in regulating cell growth and for cell-to-cell communication. Studies have suggested that calcitriol, which is the hormonally active form of vitamin D, reduces cancer progression by slowing the development and growth of new blood vessels in cancerous tissues. This increases cancer cell death thereby reducing metastases and cell proliferation. Vitamin D influences over 200 human genes, which can be impaired due to vitamin D deficiency.

Contributes to Healthy Pregnancy and Infants

a pregnant woman

Pregnant women with vitamin D deficiency are at a higher risk of developing preeclampsia and the likelihood of delivering by cesarean section. It is also associated with gestational diabetes mellitus and bacterial vaginosis. Therefore, sufficient vitamin D intake reduces the risk of developing these conditions. However, pregnant women should avoid high vitamin D intake since high levels of the vitamin is associated with an increased risk of food allergy in the child in the first two years of life.

Studies established that children with normal blood pressure who were given 2000 IU per day of vitamin D had a lower arterial wall stiffness after 16 weeks compared to those who were given 400 IU per day. Low vitamin D level is associated with a higher risk of atopic and allergic diseases, including atopic dermatitis, asthma, and eczema. Therefore, sufficient intake of Vitamin D will reduce the risk of developing these. Besides, vitamin D will enhance the anti-inflammatory effects of glucocorticoids, which is useful for supportive therapy for individuals with steroid-resistant asthma.

How Much Vitamin D Should I Take?

The question, “how much Vitamin D should I take?” is relevant since insufficient vitamin D levels in your body could lead to deficiency. How much vitamin D you need depends on many factors, including latitude, race, age, sun exposure, season, and clothing. The US Institute of Medicine recommends that an average daily intake of 400-800 IU (equivalent 10 10-20 mg) is adequate for 97.5% of individuals. If you aren’t exposed to the sun, however, your daily intake of vitamin D should be higher.

a logo og ifas university of florida

The Institute of Food and Agricultural Sciences recommended vitamin D intake is:

  • Children and teens: 600 IU
  • Adults up to age 70: 600 IU
  • Adults over age 70: 800 IU
  • Pregnant or breastfeeding women: 600 IU

In most cases, where the question “how much vitamin D should I take” arises, vitamin D blood levels above 20 ng/ml or 30 mg/ml are sufficient. In one study, it was established that daily vitamin D intake of 1120-1680 IU is needed to maintain adequate blood levels. In another study, people with vitamin D deficiency had to take 5000 IU to reach the sufficient blood levels of 30 ng/ml.

Other studies that involved postmenopausal women with vitamin D levels below 20 ng/ml revealed that taking 800-2000 IU raises blood levels above 20 ng/ml. This means that higher doses are indeed necessary to reach 30 ng/ml. Overweight people who intend to lose weight may need higher amounts of vitamin D.

Therefore, considering all these factors, a daily vitamin D intake of 1000-4000 IU (about 25-100 mg) should be enough to ensure optimal vitamin D blood levels. According to the Institute of Medicine (IOM), 4000 IU is the upper safe limit. If you need to take more than this, you should consult a health professional.

Optimal Blood Levels of Vitamin D

The answer to the question, "how much vitamin D should I take?" depends on the optimal blood levels of vitamin D. Vitamin D blood levels are assessed by measuring 25(OH)D in the blood. This is the storage form of vitamin D in the body. However, there has been a debate over the optimal blood level of vitamin D.

logo of nnc

The Nordic Nutrition Council and the IOM recommend the following vitamin D blood levels:

  • Deficient: 25(OH)D less than 12 ng/ml
  • Insufficient: 25(OH)D less than 20 ng/ml
  • Sufficient: 25(OH)D greater than 20 ng/ml

Both organizations claim that blood levels exceeding 20 ng/ml meet the vitamin D requirements of over 97.5% of the population. IOM committee did not find higher vitamin D levels to have additional health benefit but experts such as the Endocrine Society recommended aiming for higher blood concentrations of close t0 30 ng/ml.

Vitamin D Supplements and Toxicity

man having a constipation

Too much vitamin D can cause vitamin D toxicity, which is common for people who take over 10,000 IU per day, which is way above the recommended 4000 IU. Symptoms include:

  • Constipation
  • Loss of appetite
  • Feeling thirsty
  • Frequent urination
  • Feeling tired, weak, and confused


Vitamin D is vital for bone health, fighting diseases, reducing depression, weight loss, preventing cancer, and ensuring a healthy pregnancy and infants. It is produced naturally through sun exposure. However, if you live in areas where there is no sun exposure, you might develop vitamin D deficiency.

The question, “how much Vitamin D should I take?" is common. The answer is that vitamin D intake depends on your age and sex, but you should not exceed 4,000 IU. We hope that this article has adequately addressed what you need to know about vitamin D benefits and supplements, and the answer to the question “how much Vitamin D should I take?”

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