10 Surprising Reasons You Can’t Get Your Vitamin D Levels Up

When it comes to testing vitamin D status in healthy individuals (i.e., folks without medical issues, particularly those related to the liver or kidneys), the go-to status blood biomarker used in clinical practice to assess vitamin D status is total serum 25-hydroxyvitamin D, or 25(OH)D for short. 

What’s important here is the word total. You see, total 25(OH)D is the sum of both vitamin D2 (ergocalciferol) and D3 (cholecalciferol) inputs. You definitely want the sum of the parts when measuring vitamin D status because different sources offer different types: natural and fortified foods and beverages can be either D3 or D2, sunshine is D3, medication is D2, and supplements can provide D3 or D2.

Not to mention, I have also seen cases in which people supplement with vitamin D2 (which is a bad idea; we explain why here) but their healthcare provider inadvertently ordered or only reported the 25(OH)D3 lab test result. This falsely made it seem like the vitamin D supplementation regimen was ineffective. I’ve seen the opposite mistake happen too.

While the individual pieces of the puzzle are informative (sometimes they’re critical for understanding contributors to overall vitamin D status), make sure your lab report always includes the total 25(OH)D result.