For adults, a level of vitamin D in the blood of 20 nanograms per milliliter (ng/mL) or above is generally considered adequate. Levels below 20 ng/mL are generally too low for adequate bone health and overall health.
Levels above 50 ng/mL may be too high. Levels in a range that is too high or too low may affect a person’s health. The body depends on vitamin D for a variety of reasons, but it is especially important for bone health.
According to the
| Age | Amount |
| 0 to 12 months | 10 micrograms (mcg) or 400 international units (IU) |
| 1 to 70 years | 15 mcg or 600 IU |
| 71+ years | 20 mcg or 800 IU |
People who are pregnant or breastfeeding also need 15 mcg or 600 IU of vitamin D per day.
Doctors use blood tests to determine if someone has adequate levels of vitamin D. They measure vitamin D using one of two measurements: nanomoles per liter (nmol/l) or nanograms per milliliter (ng/ml).
The following table provides
| Level | Blood test result |
| Low | Less than 30 nmol/L or 12 ng/mL |
| Adequate | 50 nmol/L or 20 ng/mL or above |
| High | More than 125 nmol/L or 50 ng/mL |
It is also important to note that medical professionals generally consider a range of 30 to 50 nmol/L inadequate for a person’s bone health and overall health.
However, this may vary for different people, and research is still underway about the serum concentration linked to deficiency, bone health, and overall health.
A person can talk with their doctor to get a better understanding of what their blood test results mean.
According to the U.S. Department of Agriculture, vitamin D helps to promote and improve bone health.
Without adequate vitamin D, a person may develop soft, weak, or brittle bones. This
Vitamin D also contributes to the health of muscles, nerves, the brain, and the immune system.
Vitamin D may help to prevent some medical conditions, including some types of cancer. However, evidence from observational studies and clinical trials is
However, scientists are still trying to understand how vitamin D may influence specific conditions.
People can get vitamin D from exposure to sunlight or, to a lesser extent, from food. If someone does not get enough vitamin D from these sources, they may develop a deficiency.
The symptoms of a vitamin D deficiency can include bone and muscle weakness and pain. Symptoms may differ for osteoporosis and osteomalacia.
Causes and risk factors
Vitamin D deficiency can happen when a person does not get enough vitamin D, either from sunlight or food.
According to the U.S. Department of Health and Human Services, some people are more at risk of developing vitamin D deficiency than others. This includes:
- breastfed infants, as human milk has limited vitamin D
- older adults, as the skin does not make vitamin D as efficiently later in life
- people with dark skin, as dark skin is less able to absorb vitamin D from sunlight
- people who stay indoors for prolonged periods
- people with obesity, as fat cells bind to vitamin D and stop it entering the bloodstream
Some health conditions and medications can also make it more difficult for someone to absorb vitamin D, including:
- chronic kidney disease
- some liver diseases
- some types of cancer
- Crohn’s disease
- celiac disease
- chronic inflammatory diseases
- antiseizure medications
- gastric bypass surgery
People can get at least some of their daily vitamin D from exposure to sunlight.However, as light levels vary, depending on location and the time of year, a person may not be able to get all the vitamin D they need from sunlight.
A
Additionally, a global study in 2024 notes that the maintenance dose time ranges from 3 to 15 minutes depending on a person’s skin type and their latitude, or how high they are.
This suggests that people who live in colder climates, or who spend most of their time indoors, may benefit from vitamin D supplements. However, a person should talk with their doctor before taking vitamin D, as it can interact with some medications.
Sunlight can also cause skin damage and sunburn, so it is essential to use sunscreen when spending time outside.
A 2019 study on Australian office workers found that applying sunscreen meant people could spend more time outdoors, leading to higher vitamin D levels overall.
The study found that fish consumption, in particular, had a positive effect on vitamin D levels during winter.
According to the
- oily fish, such as mackerel, tuna, and trout
- beef liver
- some mushrooms
- chicken breasts
- some dairy products
- fortified cereals
A person can take too much vitamin D. Since vitamin D occurs naturally in only a few food sources, the most likely way a person can get too much vitamin D is through taking a high strength supplement.
The
| Age | Maximum |
| 0 to 6 months | 25 mcg or 1,000 IU |
| 7 to 12 months | 38 mcg or 1,500 IU |
| 1 to 3 years | 63 mcg or 2,500 IU |
| 4 to 8 years | 75 mcg or 3,000 IU |
| 9+ years | 100 mcg or 4,000 IU |
Vitamin D toxicity
Vitamin D toxicity refers to toxic levels of vitamin D in the body. According to a
- recurrent vomiting
- polyuria, or increased daily urine output
- confusion
- polydipsia, or an abnormal increase in thirst
- apathy
- abdominal pain
- dehydration
To help reduce the risk of vitamin D toxicity, it is important to contact a doctor for advice before taking vitamin D supplements.
A person should contact a doctor if they notice the symptoms of vitamin D toxicity. They can bring a list of any supplements they are taking to the appointment to help with the doctor’s diagnosis.
A person should also contact their doctor if they notice symptoms of a lack of vitamin D. A doctor may do a physical examination, ask questions, and perform a blood test to see if the person has a deficiency.
It is also best to contact a doctor before taking any supplements. Some supplements may interact with current medications or affect certain medical conditions.
Generally adequate vitamin D levels in the blood are 20 ng/ml or above for adults. People aged 1 to 70 years should aim to get at least 15 mcg or 600 IU of vitamin D per day. Those who are older may require more.
It is important to note that a person can also get too much vitamin D, so it is best to contact a doctor for advice.
Vitamin D is an essential nutrient for a variety of reasons, particularly for bone health. A person will often get enough vitamin D from sunlight, but if they are at risk for a deficiency they may benefit from taking a supplement.
It is important to contact a doctor before taking vitamin D supplements to reduce the risk of vitamin D toxicity.
