How we know

Reference ranges come from major reference laboratories (Mayo Clinic Laboratories, ARUP, Labcorp, Quest) and national guidelines. When labs disagree, we show the most widely used range and note the spread. Your own lab’s printed range always takes priority over ours, because it matches the method that measured your blood.

Some clinicians aim for narrower “optimal” ranges. We include one only when a source supports it, and we grade the evidence as strong, moderate, limited or expert opinion. Only strong and moderate targets appear on the range ruler. The rest are described in text, so you can see the debate without being alarmed by it.

One AI agent researches and writes each marker page. A second, independent agent then opens every cited source, re-checks every number, unit and code, and corrects what it finds. Pages carry their status: AI-verified means every number was confirmed against a source the checker opened. Expert-reviewed means a person with clinical or laboratory expertise signed off.

Every marker lists the units labs use worldwide, with conversion factors that we check automatically against the U.S. National Library of Medicine’s UCUM unit library and published molecular weights. Lab test codes (LOINC) are verified against the National Library of Medicine. The AI on this site reads documents and explains. It never calculates a number you see.

Population comparisons come from NHANES, the CDC’s National Health and Nutrition Examination Survey, analyzed with its survey weights and the CDC’s own reliability rules. Our pipeline reproduces the CDC’s published figures. NHANES describes the general U.S. population, not “healthy” people, so common doesn’t mean ideal. Analysis by Blood Test Tracker. Not endorsed by CDC, NCHS or HHS.

Blood values wobble from day to day. We use published biological-variation studies to estimate how big a change has to be before it’s unlikely to be noise (the reference change value), and we tell you which of your changes clear that bar.

We don’t diagnose, recommend doses or tell you to change medication. We don’t sell tests, supplements, ads or your data.