Before we begin: Vitamin D helps your body absorb calcium. You can get Vitamin D in three ways: through your skin, from your diet, and from supplements.
This tutorial walks you through everything you need to know about vitamin d. We explain it in plain language, step by step, so whether you are a student, a patient, or simply curious, you will come away with a solid understanding.
We cover what it is, why it matters, how it is diagnosed, and what you can do about it. Key facts are called out along the way.
Why do I need vitamin D? Vitamins are substances that your body needs to grow and develop normally. Vitamin D is important to your body because:
It helps your body absorb calcium. Calcium is one of the main building blocks of bone. A lack of vitamin D can lead to bone diseases such as osteoporosis or rickets.
It also has a role in your nerve, muscle, and immune systems:
Your muscles need it to move
Your nerves need it to carry messages between your brain and your body
Your immune system needs vitamin D to fight off bacteria and viruses
How do I get vitamin D? You can get vitamin D in three ways: through your skin, from your diet, and from supplements. Your body forms vitamin D naturally after exposure to sunlight. However, too much sun exposure can lead to skin aging and skin cancer. So many people try to get their vitamin D from other sources.
Very few foods naturally contain vitamin D. Most people get vitamin D in their diet from foods that are fortified. This means that vitamin D is added to the food. These foods may include milk, cereal, and yogurt. Foods that naturally have vitamin D include egg yolks, saltwater fish, and liver.
Vitamin D is available in supplements. It is also included in many multivitamins. The two forms of vitamin D in supplements are D2 and D3. Both types increase vitamin D in your blood, but D3 might raise it higher and for longer than D2. Vitamin D is fat soluble. You can absorb it better when you take your supplements with a meal or snack that includes some fat.
How much vitamin D do I need? The amount of vitamin D you need each day depends on your age. The recommended amounts, in international units (IU), are:
Birth to 12 months: 400 IU
Children 1-13 years: 600 IU
Teens 14-18 years: 600 IU
Adults 19-70 years: 600 IU
Adults 71 years and older: 800 IU
If you are pregnant or breastfeeding: 600 IU
But certain people may need extra vitamin D, such as:
Older adults
Breastfed infants
People with dark skin
People with certain conditions that limit the absorption of fat, such as Crohn’s disease, celiac disease, and ulcerative colitis
People who have obesity or have had gastric bypass surgery
Check with your health care provider to see if you need to take vitamin D supplements, and if so, how much you should take. Your provider may want to first do a vitamin D test to see if you are getting enough of it.
NIH: National Institutes of Health Office of Dietary Supplements
Also known as: Cholecalciferol, Ergocalciferol.
Categories: Food and Nutrition.
Source: National Institutes of Health — NIH Office of Dietary Supplements.
Key Takeaways
Understanding vitamin d is an important part of taking charge of your health. Here is what to remember:
- Know the signs — Recognizing early symptoms can lead to earlier diagnosis and better outcomes.
- Talk to your provider — If you have concerns or a family history of this condition, bring it up at your next checkup.
- Stay informed — Medical knowledge evolves. Keep learning and asking questions.
- You are not alone — Many people deal with this condition. Support groups and educational resources can help.