Vitamin D Calculator

Created by Joanna Michałowska, PhD candidate and Łucja Zaborowska, MD, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Based on research by
Holick MF, Binkley NC, Bischoff-Ferrari HA, Gordon CM, Hanley DA, Heaney RP, Murad MH, Weaver CM; Endocrine Society. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. The Journal of Clinical Endocrinology & Metabolism (July 2011)
Last updated: Jan 04, 2023

The vitamin D calculator shows you your recommended vitamin D intake according to the Endocrine Society's clinical practice guideline. It will allow you to find out how much vitamin D per day you should consume to stay healthy.

Read the article below to find out more about vitamin D, the difference between vitamin D vs. D₃, the effects of its deficiency, and how to calculate vitamin D dosage.

What is Vitamin D?

Vitamin D is a unique vitamin as it can be made **in the skin from exposure to sunlight, and this mechanism is the major natural source of this vitamin for humans. Only few foods are good sources of vitamin D, mainly oil-rich fish (such as salmon, mackerel, and herring). Other foods such as milk, margarine, and breakfast cereals are fortified with this compound in some countries.

💡 Are you interested in determining your dietary reference intake (DRI) for all vitamins according to age and sex? Then visit the vitamin calculator.

Vitamin D vs D₃

Vitamin D comes in two forms: D₂ (ergocalciferol) and D₃ (cholecalciferol). Vitamin D that comes from the skin or diet is biologically inactive and requires hydroxylation in the liver and then in the kidneys to form calcitriol - the biologically active form of vitamin D.

What is vitamin D good for?

Calcitriol circulates as a hormone in the blood, which has many different functions:

  • It plays a major role in regulating the concentration of calcium and phosphate;
  • It promotes the healthy growth and remodeling of the bone;
  • It reduces inflammation;
  • It stimulates insulin production;
  • Moreover, it is estimated that vitamin D may be responsible for regulating up to 200 genes that may facilitate many of the pleiotropic health benefits.

What is vitamin D deficiency?

Two vitamin D metabolites (25-hydroxyvitamin D or 25(OH)D) are measured in serum to determine the patient's vitamin D status, where:

  • Vitamin D deficiency is defined as a 25(OH)D below 20 ng/ml (50 nmol/liter).

  • Vitamin D insufficiency as a 25(OH)D of 21–29 ng/ml (52.5 – 72.5 nmol/liter).

Following these definitions, it has been estimated that 20 –100% of U.S., Canadian, and European older adults and women are vitamin D deficient. Children and adults are at equally high risk for vitamin D deficiency and insufficiency worldwide. The major cause of vitamin D deficiency is inadequate exposure to sunlight. Moreover, high BMI and administration of some medications (e.g. corticosteroids) is also associated with a higher risk of vitamin D deficiency. Learn more about BMI and corticosteroids with the BMI (body mass index calculator) and steroid conversion calculator.

Consequences of vitamin D deficiency:

  • Abnormalities in calcium, phosphorus, and bone metabolism, e.g., rickets in children, osteopenia and osteoporosis in adults; and
  • Muscle weakness.

How to calculate vitamin D dosage?

Various institutions have proposed different recommendations for the amount of daily intake of vitamin D. The recommended dose may vary according to:

  • Age;
  • Pregnancy or lactation;
  • Weight status;
  • Skin color (fairer skin synthesis vitamin D easier); and
  • Serum vitamin D level.

In general, if you have fair skin, try to get at least 10 minutes of noon sunshine per day to meet your vitamin D needs. If you have darker skin, this amount changes to 30 minutes.

💡 We can describe vitamins by measuring their bioeffect with IU (International Units) or by calculating their weight with mcg or mg (micrograms or milligrams). Find out more in the mcg to IU converter.

Vitamin D calculator for adults and children

Our vitamin D calculator for adults and children uses Endocrine Society Clinical Practice
Guideline's recommended intakes of vitamin D. You can find two different recommendations:

  • Recommended dietary intakes of vitamin D for patients at risk for vitamin D deficiency; and
  • Recommended intakes of vitamin D for treatment of vitamin D deficiency.

↪️ You will be able to see the latter only if you know your vitamin D serum level and when it turns out that you are vitamin D deficient based on your result.

Joanna Michałowska, PhD candidate and Łucja Zaborowska, MD, PhD candidate
Do you know vit. D serum level?
Adults aged 18 - 50 yrs require at least 600 IU of vitamin D a day to maximize bone health and muscle function.

The dose of at least 1500 – 2000 IU may be needed to raise the blood level of vit. D to consistently above 30 ng/ml.

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