Should You Test Your Vitamin D Levels? A Psychiatrist’s Perspective

There is an ongoing debate in medicine about vitamin D testing. Some guidelines recommend against routine testing in most populations. Others argue for more liberal testing. As someone who practices integrative psychiatry and regularly orders comprehensive lab panels, I have a particular perspective on when testing makes sense and when it might not.

Why I Include Vitamin D in My Standard Workup

When a patient comes to me with depression, anxiety, or other mental health concerns, I am looking for anything that might be contributing to their symptoms or impeding their recovery. Vitamin D deficiency is common, easy to test for, and when present, easy to address.

My reasoning is straightforward: if someone has depression and also has vitamin D deficiency, I want to know about it. Correcting that deficiency probably will not cure their depression on its own, but it removes one potential obstacle to recovery. And the test is simple and relatively inexpensive.

When Testing Makes the Most Sense

You have depression and risk factors for deficiency. This is the highest-yield scenario. If you are depressed and also have darker skin, limited sun exposure, obesity, or live at a northern latitude, the probability of deficiency is high enough that testing provides actionable information.

Your depression is not responding well to standard treatment. When someone has treatment-resistant depression, it makes sense to look for any contributing factors that might be addressable. Vitamin D deficiency is one of many things worth checking.

You are starting a comprehensive treatment plan. If you are beginning work with a new psychiatrist or mental health provider and they are doing thorough baseline assessment, vitamin D is a reasonable inclusion along with thyroid function, basic metabolic panel, and other relevant labs.

Before starting supplementation. If you are going to take vitamin D for mental health reasons, knowing your baseline level helps determine appropriate dosing and gives you a reference point to assess whether supplementation is working.

Understanding Your Results

The test you want is serum 25-hydroxyvitamin D, sometimes written as 25(OH)D or calcidiol. This is the main circulating form and the standard marker for vitamin D status.

Reference ranges vary between laboratories, which can be confusing. Here is a general framework:

Below 30 nmol/L (12 ng/mL): Severe deficiency. Definitely address this.

30 to 50 nmol/L (12 to 20 ng/mL): Deficiency. Should be corrected.

50 to 75 nmol/L (20 to 30 ng/mL): Insufficiency. Many experts recommend improving to higher levels.

75 to 125 nmol/L (30 to 50 ng/mL): Adequate. This is where you generally want to be.

Above 125 nmol/L (50 ng/mL): High normal. Generally fine but no additional benefit for most purposes.

How Often to Retest

If you are deficient and start supplementation, retesting in 8 to 12 weeks makes sense to confirm you are reaching adequate levels and to guide any dose adjustments.

Once your levels are stable in the adequate range, annual testing is usually sufficient unless your circumstances change significantly (major weight gain or loss, change in sun exposure, new medications that affect vitamin D metabolism, etc.).

What Testing Does Not Tell You

A normal vitamin D level does not guarantee your mental health symptoms are unrelated to vitamin D metabolism. And a low level does not mean vitamin D deficiency is the primary cause of your depression.

Testing tells you one piece of information: your current vitamin D status. Whether correcting deficiency will improve your mood requires actually trying it and seeing what happens.

References

1. Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment, and prevention of vitamin D deficiency: An Endocrine Society clinical practice guideline. Journal of Clinical Endocrinology and Metabolism. 2011;96(7):1911-1930.
2. Ross AC, Manson JE, Abrams SA, et al. The 2011 report on dietary reference intakes for calcium and vitamin D from the Institute of Medicine: What clinicians need to know. Journal of Clinical Endocrinology and Metabolism. 2011;96(1):53-58.
3. LeFevre ML, US Preventive Services Task Force. Screening for vitamin D deficiency in adults: US Preventive Services Task Force recommendation statement. Annals of Internal Medicine. 2015;162(2):133-140.