Vitamin D deficiency: How do I know if I'm low in vitamin D?

Vitamin D deficiency: How do I know if I'm low in vitamin D?
Aug 15, 2016

It is not uncommon these days for their healthcare practitioner to recommend a vitamin D supplement, even though there are no signs of vitamin D deficiency.[1] Nevertheless, this gets us thinking…why? Is there a problem? Could you have vitamin D deficiency? It is always best to clarify and discuss this with your healthcare professional. It is also a good idea to learn more.

How do people know if they are low in vitamin D?

Experts define vitamin D deficiency in terms of blood levels. There are different degrees of ‘low’ vitamin D blood levels that characterize the range of vitamin D deficiency, and these vary from country to country and region to region based on localized vitamin D recommendations.

The blood test is reported in different values for different countries. There are other blood tests (i.e. calcium, phosphorus, 25(OH)D, etc.) and sometimes a bone scan is also considered. Physicians will typically do a physical examination, with special attention to bone formation and muscle strength. They may also ask you about tenderness. The vitamin D blood test:[2]

Medical professionals determine whether somebody is vitamin D deficient or not by doing a simple blood test. The blood test is actually designed to look for a marker of vitamin D in the circulating blood, 25-hydroxyvitamin D or 25(OH)D₃ or 25(OH)D (calcidiol) – the major metabolite of vitamin D₃ found in the bloodstream. In the United States, most vitamin D lab results are reported in ng/mL. In Canada and the UK, values are reported in nmol/L. (See the table below).

Some people lack vitamin D more than others; therefore, experts have developed a ‘vitamin D nutrition status’ scale. In Canada, the sufficiency cut-off is higher than in the US and UK. The table below describes the range of vitamin D and health in North America.


United States: Serum 25-Hydroxyvitamin D [25(OH)D] Concentrations and Health*[3]

 Serum 25(OH)D, range  Vitamin D nutritional status
 >50 ng/mL (>125 nmol/L)  Evidence links potential adverse effects to such high levels, particularly >150 nmol/L (>60 ng/mL)
 >20 ng/mL (50 nmol/L)  Sufficiency  (desirable optimal for fracture prevention)
 12-20 ng/mL (30-50 nmol/L)  Insufficiency
 <12 ng/mL (>125nmol/L)   Deficient (diagnostic of nutrition deficiency, rickets or osteomalacia).

Conversion Factor for nmol/L: ** 1 nmol/L = 0.4 ng/mL


Canada: Circulating levels of 25- hydroxyl-Vitamin D or 25(OH)D₃ by vitamin D nutrition status[3]

 Serum 25(OH)D, range  Vitamin D nutritional status  
>600 nmol/L (>240 ng/mL) Vitamin D toxicity
<225 nmol/L (<90 ng/mL) Physiologic range from exposure to sunlight (or UV light)
<75 nmol/L (>30 ng/mL) Sufficiency (desirable optimal for fracture prevention)
<40 nmol/L (<16 ng/mL) Insufficiency
<25 nmol/L (>10 ng/mL) Deficient (diagnostic of nutrition deficiency, rickets or osteomalacia)

Conversion Factor: ng/mL x 2.5075


What is the optimal vitamin D level?

The answer is not as easy as it sounds. There are differences in opinions about what is “vitamin D deficiency” and what is “vitamin D insufficiency”. Why these two classifications anyway? A wide “optimal” range for vitamin D blood levels or 25(OH)D is reported between 25-80 ng/mL or 50 nmol/L – 225nmol/L.[5]

To test vitamin D blood levels… or not test?

In some regions, for example in Canada, physicians do not routinely test vitamin D blood levels on healthy individuals, unless they suspect vitamin D deficiency.[6] Since many Canadians are low in vitamin D, health authorities recommend that people should focus on getting enough vitamin D either naturally and/or with supplementation instead of going to the trouble and cost of having a blood test.

Many healthcare professionals, guided by their practical experience, recommend vitamin D supplementation without testing, even if their patients have no obvious risk factors or signs of deficiency[7]. This is the same with infants. This is likely because their patients generally have inconsistent or limited daily sun exposure and/or they have little vitamin D intake in daily food.

Vitamin D blood tests can be helpful for healthcare practitioners to evaluate a suspected case of vitamin D deficiency and allow them to diagnose, monitor, and treat the condition if necessary.

Talk to your healthcare practitioner about your individual vitamin D status and needs. Remember, Ddrops® products are not indicated to treat or correct vitamin D deficiencies; Ddrops® are intended to help maintain healthy blood levels of vitamin D.



About the author:

Susan Jankus | Ddrops

Susan works in our marketing department, but she is a science geek at heart. She has degrees in biology and pharmacology and love researching scientific content. In whatever spare time she has, Susan is trying to keep up with her teenage kids and sneaks out for walks with her dog, Sugar.

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