There's No Such Thing As A Vitamin D Deficiency - Part 2

Who needs to take a supplement?

Look at that, another stock photo that I don’t think I’ve used in my 444 blogs over the last decade. Photo by Maria Kozyr on Unsplash

This is part 2 of my series looking at the US Endocrine Society guidelines about vitamin D testing and supplementation for the prevention of disease. In part 1, we talked about how the Society had basically eliminated the idea of a deficiency or an insufficiency from their dictionary. There’s simply no good way to define “low” vitamin D in a meaningful way, and therefore the argument of the Endocrine Society is that we should base the decision to use a supplement on randomized trials showing a benefit instead.

Very sensible decision, given the morass of evidence surrounding vitamin D.

So the Society no longer recommends that asymptomatic people get tests of their vitamin D levels. But there are some groups of people who don’t have symptoms that the Society does recommend take a supplement:

1. People over age 74

2. People under age 18

3. Pregnant people

4. People with prediabetes

Importantly, they also don’t discuss people who have specific diseases in these guidelines. There are some specific disorders where taking a vitamin D pill might be beneficial—these guidelines are only for preventing disease, not treating it.

Unfortunately, even in the year since publication, the guidelines have become a bit outdated. While it might have been reasonable to say that there’s good evidence for vitamin D supplementation in these four groups in 2024, it’s not so clear in 2025.

Let’s look at the data.