By Jordan Stachel, MS, RDN, CPT

Vitamin D is an essential fat-soluble vitamin needed for several functions in the body. Vitamin D deficiency is relatively common and easily treatable for most people. Vitamin D levels can be easily tested and checked yearly or as needed to help ensure deficiency does not occur. Read this article to learn more about the vitamin D deficiency symptoms and the fastest way to check.

What Is Vitamin D?

Vitamin D, also known as calciferol, is found in foods, in sunlight, and in supplements.^[1] Food sources that are rich in vitamin D include fatty fish, beef liver, egg yolk, cheese, and some fortified foods.^[1] You can also get vitamin D through exposure to the sun and/or by taking supplements. If you are interested in taking a vitamin D supplement, it is essential to consult a qualified healthcare provider. They can check your vitamin D levels to ensure you are taking a safe amount and that it is appropriate for you to supplement.

Vitamin D has several roles in the body, including:^[1]

• Promotion of calcium absorption
• Bone growth
• Reduction of inflammation
• Promotion of cell growth
• Helps optimize immunity
• Helps optimize glucose metabolism

Due to vitamin D’s essential roles in the body, it is best to avoid becoming vitamin D-deficient.

Symptoms of Vitamin D Deficiency

Vitamin D deficiency can cause many different symptoms to present. Some of these include:^[2]

• Rickets, a rare condition that can lead to incorrect growth patterns, muscle weakness, or deformities
• Fatigue
• Muscle cramping
• Depression

It is also entirely possible to have no symptoms of vitamin D deficiency. This is why it is crucial to have your levels tested to ensure they are within an optimal range. Symptoms can also vary by age, and there are special considerations for infants’ vitamin D levels.^[2] Generally, a blood level of around 50 nmol/L is considered sufficient. Some people may need to be at a higher blood level for health optimization. Deficiency of vitamin D is typically defined as levels below 30 nmol/L in adults.^[1]

How to Test for Vitamin D Deficiency

If you want to test your vitamin D levels, your healthcare provider can run a simple blood test. You may need to request this test, as it is not standard for all care providers to measure vitamin D levels.^[3] Also, your healthcare provider may not check your vitamin D levels unless you have symptoms of deficiency or a medical condition that warrants screening.

Some conditions that may warrant more frequent screening for vitamin D deficiency include:^[3]

• Bone diseases like osteopenia, osteomalacia, or osteoporosis
• Less exposure to the sun or wearing too much sun protection
• Malnutrition or deficiencies in key nutrients
• A history of weight loss surgery
• Malabsorption
• Medical conditions like Crohn’s disease, celiac disease, or liver disease
• Use of certain medications
• A family history of low vitamin D

During a vitamin D test, you can expect the same protocol as any other standard blood test. There are no special concerns you need to consider to have your vitamin D levels tested.

There are also testing options you can take from the comfort of your own home to check vitamin D levels. Everlywell offers an at-home Vitamin D and inflammation test that looks at the vitamin D levels in your blood as well as the levels of C-reactive protein, which is the primary marker of inflammation in the body. With an easy-to-use finger-prick sample, your results are sent in, and you will receive your vitamin D levels and the next steps.

Any blood test is considered a quick option and likely the fastest way to check your vitamin D levels. Choosing an at-home option may save you even more time than having the test done at a healthcare provider’s office.

How to Interpret Results and Optimize Vitamin D

If your test results come back as vitamin D deficient, you can work with your healthcare provider to come up with the following steps to remedy your status. Depending on the cause of the deficiency, treatment will vary. Some standard treatment options to remedy the vitamin D deficiency include:^[4]

• Supplement with the appropriate type and amount of vitamin D for you.
• Take enough other nutrients, such as calcium, to support vitamin D absorption and metabolism.
• Bolster the diet with vitamin D-rich foods.
• Remedy any malabsorption issues that may be occurring.
• Calculated exposure to natural sunlight for safe periods of time.

Optimize Your Vitamin D Today With Everlywell

Vitamin D deficiency is common and usually straightforward to treat and optimize. The first step is to have your levels tested to determine what you need to get your vitamin D into the right range. Vitamin D deficiency is not something to ignore, as symptoms can be uncomfortable and dangerous for your health if they progress. Get started today by seeing where your vitamin D levels stand with Everlywell.

References

1. Office of Dietary Supplements - Vitamin D. Last reviewed June 27, 2025. Accessed November 19, 2025. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
2. Vitamin D deficiency. Cleveland Clinic. Published September 24, 2025. Accessed November 19, 2025. https://my.clevelandclinic.org/health/diseases/15050-vitamin-d-vitamin-d-deficiency
3. Vitamin D test. Last reviewed December 4, 2024. Accessed November 19, 2025. https://medlineplus.gov/lab-tests/vitamin-d-test/
4. Vitamin D Deficiency. Yale Medicine. Published April 22, 2024. Accessed November 19, 2025. https://www.yalemedicine.org/conditions/vitamin-d-deficiency