Reading Your Vitamin Panel

Vitamin D is one of the most commonly deficient nutrients tested, and one of the most commonly misread results, because two different units are in use.

Niacin is one of the few vitamins your body can partly build for itself, which is exactly why a plasma level is a weak way to judge whether you're getting enough.

Serum copper is one of the most misread numbers on a vitamin panel. Most of it is locked inside a liver protein that swings with inflammation and hormones, not with how much copper you eat.

Calcitriol is the active form of vitamin D, but the test almost everyone wants is the other one, and confusing the two is one of the most common lab mix-ups there is.

MTHFR is the rare lab test that's heavily marketed to worried people and quietly discouraged by the medical bodies who wrote the guidelines. Here is why both things are true.

Chromium circulates in such tiny amounts that the lab can barely resolve it, which is why most chromium results say less than people assume.

Most nutrient tests screen for a shortfall. Manganese is the rare one run almost entirely to catch an excess, because going short is something healthy people essentially never do.

Serum zinc is one of the easiest blood numbers to misread. An infection, a recent meal, or low albumin can pull it down while your body's zinc stays exactly where it was.

Why selenium results depend on the lab and the sample type, who is at risk of a low level, the signs of selenosis, and what the evidence says about selenium and the thyroid.

Your blood carries only about 1% of your vitamin A, and your liver works to hold that fraction steady. So the test can read fine while the reserve behind it quietly falls.

The direct blood level of vitamin K is one of the least-ordered nutrient tests there is, because a cheap, everyday clotting test already answers the question that matters.

Most vitamin shortfalls take months or years to show up on a blood test. Thiamine is the rare one that can empty out in a couple of weeks, which is why it goes unflagged until the symptoms are already loud.

Riboflavin is the B vitamin that switches the others on. When it runs low, your B6 and folate results can fall with it, while B2 itself stays easy to miss.

Three authorities draw the line between deficient and fine in three different places, which is how one result gets flagged at one lab, printed as normal at another, and called unresolved by a national guideline.

Fortified flour made classic folate deficiency rare, so today this number is read mostly for one reason: a folate result can repair the blood picture of a B12 shortage while the nerve damage underneath keeps going.

Vitamin B6 runs more than a hundred reactions and never asks for credit. The strange part: the pills sold to protect nerves, taken long enough at high doses, are what injures them.

Ascorbate starts breaking down the moment blood leaves the arm. Getting the plasma into the dark and into a freezer is half of what makes this result trustworthy.

A serum vitamin E number rides on your blood fats, so a high reading can mean little more than high cholesterol. That is why the most accurate labs read it against the lipid ratio.

Methylmalonic acid is the test almost nobody meets until a B12 result comes back ambiguous. It rises when cells run short of B12 but not when folate is low, which makes it the deciding read on a borderline number, as long as the kidneys clear it normally.