If you're not getting enough vitamin D from your diet and natural sunlight, supplements may be the solution to those vitamin d deficiency symptoms.

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“Your vitamin D levels are in the toilet,” said my primary care physician, a naturopathic doctor who’s not one to mince words. Sure enough, my level of 25-hydroxy­vitamin D—usually abbreviated 25(OH)D or sometimes 25-OH-VitD, turned out to be low. As we know, 25(OH)D is the compound that’s measured in the blood to check vitamin D levels. The lab (LabCorp) used reference ranges that reflect the Endocrine Society’s definition of vitamin D deficiency. [1,2]

“But I take 5,000 IUs a day,” I replied. Even though I’d seen low vitamin D levels in some of my own patients despite regular supplementation with 5,000 IUs or more, I was surprised at how much my own body seemed to require to maintain sufficient levels, let alone optimal ones.

“Well, you need to start taking 10,000 IUs,” my doctor told me. I probably won’t need to take this dose forever—just until my vitamin D levels come back up into a more optimal range. Once there, I can drop my dose back down.

Sunshine is a key source of vitamin D, but our diet (especially during winter months) can help us avoid vitamin D deficiency. See graphic below.

My goal is to find the dose that will keep my levels optimal but not too high, which can be dangerous—vitamin D toxicity, as it’s called. As with some of my patients, it seems as though I may need more than 5,000 IUs per day, especially during the winter months, to avoid vitamin D deficiency symptoms.

There are differing opinions about vitamin D levels. In The Journal of the American Medical Association in 2015, an editorial recommended that physicians “avoid overscreening and overprescribing supplemental vitamin D.” The JAMA authors argued that given the “lack of convincing evidence for non-bone benefits of vitamin D,” doctors shouldn’t screen for vitamin D deficiency or recommend their patients take more than the current dietary allowance (RDA) for vitamin D: 600 IU per day for persons aged 1 to 70 years and 800 IU per day for those 71 years and older.[3]

Why Test Vitamin D Levels?

You’re likely aware of the huge surge in research showing that vitamin D plays a crucial role in a plethora of physiological and preventive functions. Not only does it regulate calcium and phosphate levels, as we thought, but vitamin D also has numerous extra-skeletal effects.

Your vitamin D level can affect bone and tissue health, cell growth modulation, your immune system, and teeth. Food choices like portobello mushrooms, egg yolks, fatty, oily fish, cheese, and fortified cereals are excellent choices to help prevent vitamin D deficiency.

Acting as a hormone, vitamin D can have a significant impact on the cardiovascular system, central nervous system, endocrine system, and immune system.[4] Vitamin D receptors have now been found in most body cells. It is believed that when vitamin D binds to these receptors, it regulates a very large number of genes in the human genome.[5]

The research associates vitamin D deficiency with many acute and chronic illnesses, including autoimmune diseases [6], cancer [7], type 2 diabetes and insulin resistance [8], infectious diseases (including the common cold) [9], cardiovascular disease [10], cognitive decline [11], and more.

While more research is needed, many vitamin D researchers and physicians, including Boston University’s Dr. Michael Holick, PhD, MD, one of the one of the world’s most prominent vitamin D researchers, disagree with the JAMA author’s stance on staying with low-dose vitamin D. Instead, they support the idea of increasing vitamin D levels through high-dose supplementation.[12]

How to Get Tested for Vitamin D Deficiency

A vitamin D test can tell you whether you’re dealing with vitamin D deficiency or, as it’s called, vitamin D toxicity. ( © Katarzyna Bialasiewicz | Dreamstime.com)

If your goal is to prevent these common conditions, achieve optimum health, or age more gracefully, you’ll want to regularly test your vitamin D levels and adjust your dose accordingly. Blood testing for 25(OH)D is only way to know whether you’re getting enough—or too much—vitamin D. March or April (the end of winter) is an excellent time of the year to test.

You have three options for a vitamin D deficiency test:

• Ask your doctor to order it.
• Order it yourself online from a “direct-to-consumer” business like Request A Test or DirectLabs, and go to a local laboratory draw site for the blood draw.
• Order an in-home finger prick test from a website like the Vitamin D Council or ZRT Laboratory. Options 2 and 3 are not permitted in all states.

Make sure the test is the correct one: Even some doctors mistakenly order a 1,25(OH)₂D test instead of the correct 25(OH)D test.

Vitamin D Deficiency: Facts, Figures, and Further Reading

For more on the symptoms, causes, and effects of vitamin D deficiency, see these posts:

• “Natural Remedy for High Blood Pressure: Vitamin D“
• “Natural Food Sources of Vitamin D“
• “Are You Getting Enough Vitamin D To Prevent Osteoporosis Symptoms?“

And don’t miss our post “10 Vitamin D Deficiency Symptoms You Can Identify Yourself.”

Use our Comments section below to offer your experiences with vitamin D and whether you’ve experienced symptoms associated with deficiency or toxicity.

1. LabCorp Test Menu. Vitamin D, 25-hydroxy.
2. J Clin Endocrinol Metab. 2011 Jul;96(7):1911-30.
3. JAMA. Published online February 19, 2015.
4. Dermatoendocrinol. 2013 Jun 1; 5(3): 331–347.
5. Best Pract Res Clin Endocrinol Metab. 2011 Aug;­25
(4):543-59.
6. Autoimmun Rev. 2012 Dec;12(2):127-36.
7. Oncologist. 2011;16(9):1215-27.
8. Diabetologia. 2012 Aug;55(8):2173-82.
9. Inflamm Allergy Drug Targets. 2013 Aug;12(4):239-45.
10. Clin Endocrinol (Oxf). 2011 Nov;75(5):575-84.
11. Neurology. 2014 Dec 9;83(24):2292-8.
12. http://drholick.com/

Originally published in 2016, this post is regularly updated.