It can be confusing to notice several different forms of vitamin D. Here we explain various forms (D2, D3, and 25-hydroxy D) and how to test your levels, especially with the recent popularity and convenience of at-home test kits.
Vitamin D, often called the "sunshine vitamin," is necessary for many functions, from strong bones to immune health.
Unlike other vitamins, that are get from our daily diets, vitamin D can be made by the body on exposure to sunlight.
However, several factors can affect vitamin D production, making it necessary to understand the different forms of vitamin D and how to ensure you have the adequate levels.
Vitamin D is not a single nutrient but a group of fat-soluble secosteroids.
They are responsible for increasing absorption of calcium, magnesium, phosphate, and other minerals.
While often referred to as a vitamin, vitamin D acts more like a hormone, influencing numerous physiological processes.
There are two main forms of vitamin D that are relevant to our health:
vitamin D2 (also called ergocalciferol)
vitamin D3 (also called cholecalciferol).
Vitamin D2 is produced by plants and fungi when exposed to ultraviolet (UV) light, while vitamin D3 is produced in the skin when exposed to UVB rays from sunlight.
Both forms are biologically inactive and must undergo conversion to more active forms in the body to become usable.
The most accurate way to know vitamin D levels is by measuring the amount of 25-hydroxy vitamin D [or 25(OH)D] in the blood.
This is the primary form of vitamin D circulating in the blood and has the total amount of vitamin D from both diet and sun exposure.
25(OH)D includes both 25-hydroxy vitamin D2 [25(OH)D2] and 25-hydroxy vitamin D3 [25(OH)D3].
Vitamin D plays a very important role in absorption of calcium, which is essential for maintaining strong bones and preventing osteoporosis.
It also contributes to immune function, muscle strength, and cell growth.
Research suggests that adequate vitamin D levels may also reduce the risk of certain chronic diseases, such as type 1 diabetes, multiple sclerosis, and some types of cancer.
Exposure to sunlight is the primary source of vitamin D.
However, factors like sunscreen use, time of day, season, distance from the equator, and skin pigmentation can significantly affect vitamin D production.
That's why many northern countries have chronic vitamin D deficiency.
Common sources of vitamin D in our diets include fatty fish (salmon, tuna, mackerel), egg yolks, fortified foods (milk, cereals, orange juice), and supplements.
Vitamin D deficiency is a common problem across the world.
It occurs when the body doesn't have enough vitamin D to function properly.
Symptoms of deficiency can be subtle and very difficult to find out.
Insufficient vitamin levels may cause fatigue, bone pain, muscle weakness, and higher susceptibility to infections.
A simple blood test can measure your 25-hydroxy vitamin D levels.
At-home vitamin D test kits offer a convenient and accessible way to monitor your levels without needing a doctor's visit.
These tests typically require a small amount of blood sample with a finger-prick that you collect and mail to a lab for analysis.
Results are usually available online within a few days.
Your doctor can interpret your test results and recommend appropriate follow up based on your needs.
The Endocrine Society recommends optimal 25(OH)D levels to be generally above 30 ng/mL.
Levels below 20 ng/mL are considered deficient, while levels between 20 and 30 ng/mL are considered insufficient.
Higher levels rarely have any side effects, so it might be better to raise them further, if possible.
Only values over 100 or 150 might cause toxicity and kidney stones in some people. But such high levels require large amount of supplementation for a very long time.
Maintaining adequate vitamin D levels is helpful for an overall optimal health.
Understanding the different forms of vitamin D, their importance, and how to test your levels empowers you to take proactive steps towards better health.
Convenient at-home testing options make monitoring your vitamin D status easier than ever.
Order an at-home Vitamin D Test kit.
All About Vitamin D - a brief summary of the sunshine vitamin.
The Most Common Signs of Vitamin D Deficiency - learns the signs before you get tested.
The Best Ways To Manage Your Vitamin D Levels - tips on managing your levels.
Cardiovascular Disease and Vitamin D - understand the crucial role vitamin D plays in heart health.
CRP, Inflammation, and Risk of Heart Disease - C-reactive protein, Vitamin D & their role in inflammation.
3. Prevalence and correlates of vitamin D deficiency in US adults
