Testing for vitamin D

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Having blood tests to measure the amount of vitamin D in your blood is the only way to know if you’re getting enough vitamin D or not. The blood test you need is called a 25(OH)D blood test.

You can get a blood test at your doctors or you can do an in-home test or get a test at a laboratory. All of these methods of testing should give you accurate results.

In-home tests are easy to use and involve pricking your finger to take a small blood sample and sending this away to a laboratory for testing.

Your tests results will show whether you’re getting enough vitamin D or not, and whether you may need to take supplements or expose your skin to the sun more. Different organizations in the United States recommend different ideal vitamin D levels. The Vitamin D Council suggests that a level of 50 ng/ml is the ideal level to aim for.

How do I get tested?

There are three ways to get tested:

  1. Ask your doctor for a vitamin D test. Be specific and ask for a 25(OH)D test. There is another type of blood test for vitamin D, called  a 1,25(OH)₂D test, but the 25(OH)D test is the only one that will tell you whether you’re getting enough vitamin D.
  2. Order an in-home test. These tests are sent to your home. You prick your finger and put a drop of blood on to some blotter paper. You send the paper to a laboratory to be tested.  In-home test kits are a convenient option for those who prefer to take a vitamin D test in the comfort of their own home. The Vitamin D Council sells the most affordable in-home 25(OH)D test kit available in the United States.
  3. Order a test online and get blood work done at a laboratory. In the United States, there are a few websites in which you purchase an in-home vitamin D test online, and then, you attend the laboratory closest to you. These tests are more expensive than in-home tests.

All three ways of getting tested should give you an accurate result.

How do I use a Vitamin D Council in-home test kit?

Vitamin D Council has partnered with Heartland Assays to make available our own in-home vitamin D test kit. The test involves sending small samples of blood to Heartland Assays. Vitamin D Council’s in-home test kit can be used to test vitamin D levels in both adults and children.

This is how the Vitamin D Council test works:

  1. After ordering your test kit, you must activate your test kit. To do this, click the tab at the top right corner titled, “Activate test kit.”
  2. Fill out the required information, including the serial number located on the blood spot card and the 5-digit passcode listed on your instruction card.
  3. Included in the test kit is a blood spot card with unique ID number, two lancets, an alcohol prep pad, a sterile gauze pad, bandage, and a return envelope and label.
  4. Read the instruction card included in the test kit and follow each step carefully to ensure proper blood spot collection. You can also watch our instructional video for additional clarification.
  5. Make note of your serial number so you can easily find your results when they are ready.
  6. Do NOT write your name on the blood spot card or return envelope. Heartland Assays will not be able to process your order if your name is on any of the materials returned to the lab.
  7. Once you’ve completed the spot collection, mail your spot card using the return envelope. If you live in the United States, you don’t need to pay any return shipping costs.
  8. For domestic orders, please allow 5 business days from when you send your spot card for Heartland Assays to receive it. Please allow anywhere between 2-6 weeks for the blood spot card to arrive at the lab for international orders.
  9. When Heartland Assays receives your spot card, you will receive an email within 7-14 business days notifying you that your results are ready.
  10. Log in to your account on the Vitamin D Council website to see your results.

What do the results mean?

When you get your test results you will see a number in units of ng/ml, for example, 50 ng/ml. These are the units that health professionals in the United States use. Elsewhere in the world, vitamin D blood test results are given in units of nmol/l.

To convert a test result measured in nmol/l to one measured in ng/ml, divide the nmol/l number by 2.5. For example, 50 nmol/l is the same as 20 ng/ml (50÷2.5).

To convert a test result measured in ng/ml to one measured in nmol/l, multiply the ng/ml number by 2.5. For example, 20 ng/ml is the same as 50 nmol/l (20 x 2.5).

These are the ranges that different organizations in the United States use to say whether you’re severely lacking in vitamin D (deficient), mildly lacking in vitamin D (insufficient) or whether you’re getting enough vitamin D (sufficient):

Vitamin D 25(OH)D range guidelines from various organizations:
Vitamin D Council Endocrine Society Food and Nutrition Board Testing Laboratories
Deficient 0-30 ng/ml 0-20 ng/ml 0-11 ng/ml 0-31 ng/ml
Insufficient 31-39 ng/ml 21-29 ng/ml 12-20 ng/ml
Sufficient 40-80 ng/ml 30-100 ng/ml >20 ng/ml 32-100 ng/ml
Toxic >150 ng/ml

The Vitamin D Council suggests that a level of 50 ng/ml is the ideal level to aim for. This is why the Council recommends that adults take 5,000 IU/day of vitamin D supplement in order to reach and stay at this level.

The Endocrine Society recommends taking a vitamin D supplement of around 2,000 IU/day to reach and stay above a level of  30 ng/ml. This is what the Endocrine Society recommends as the ideal level to aim for. Lastly, the Food and Nutrition Board recommends 600 IU/day of vitamin D supplement because they believe 20 ng/ml is the ideal level to aim for.

What should you do based on your test results?

  • If you tested low and want a higher level, you need to get more sun exposure or take a larger daily supplement.
  • If you tested and are right where you want to be, continue your supplement and sun exposure routine. Keep in mind that your level in the summer is probably higher than in the winter, with more sun and UVB. So you may need to supplement more in the winter than in the summer to have the same vitamin D level.
  • If you tested high and want a lower level, you need to take a smaller daily supplement.

You do not want to have a level over 100 ng/ml and in fact anything over 150 ng/ml is considered toxic. Go to the following pages for more information about your results, supplementation, and sun exposure:

References

  1. 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. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30.
  2. Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
  3. Vieth, R. “The Pharmacology of Vitamin D.” In Vitamin D, Third Edition, by Feldman D, Pike JW and Adams JS. Elsevier Academic Press, 2011.

 

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