Vitamin D Isn't One-Size-Fits-All: How Your Genes Set Your Ideal Level

You've probably had your vitamin D levels tested at some point. Maybe your doctor said they were low and told you to take a supplement. Standard advice, standard dose.

But here's what most people don't realize: your genes play a major role in how your body produces, converts, transports, and uses vitamin D. And that means the "right" level — and the right dose to get there — looks different for everyone.

The VDR gene

The vitamin D receptor (VDR) gene determines how effectively your cells respond to vitamin D once it's circulating in your blood. Some people have VDR variants that make their receptors less sensitive, meaning they may need higher circulating levels to get the same cellular benefit.

Conversion and transport

Your body doesn't use the vitamin D you take directly. It has to be converted — first in the liver, then in the kidneys — into its active form. Genetic variants in the CYP enzymes responsible for this conversion can slow the process down.

There's also a binding protein (GC gene) that carries vitamin D through your bloodstream. Variants in this gene can affect how much of your vitamin D is actually bioavailable versus just floating around, bound and unusable.

What this means in practice

Two people can take the same vitamin D supplement, in the same dose, and end up with completely different outcomes. One might absorb and convert it efficiently. The other might need a different form, a higher dose, or cofactors like magnesium and K2 to support the process.

Your Mosaic report

Your Mosaic report includes your vitamin D-related gene variants as part of the Micronutrients section, covering receptor sensitivity, conversion efficiency, and transport. It gives you and your practitioner the information you need to stop guessing and start supplementing based on your biology.