
Understanding Your Labs: What I Check, Why, and What the Numbers Mean
Heart & Labs · Testing
A lab result is a clue, not a verdict. Here is what each one tells us, and what it cannot.
Written for my patients. If you are not one, read "call me" as "call your own clinician", and take the questions here to them.
First: what "normal" means
A lab's reference range usually describes the middle 95 percent of the people that lab has tested. That is a statistical description of a population, not a picture of health. You can sit inside every range and still be heading somewhere you do not want to go, and one number slightly outside a range often means nothing at all.
I also watch for the opposite problem. The "optimal ranges" that circulate online are often invented, with no research behind them, and they turn healthy people into worried ones. I use targets that are tied to real outcomes, and I care more about your trend over time than about any single result.
Blood sugar and insulin
Heart risk
Organs, thyroid and blood
About vitamin D
In 2024 the Endocrine Society advised against routine vitamin D testing in healthy adults, because no study has shown that testing and treating to a target level improves health. Most healthy adults under 75 need only the standard daily amount, 600 to 800 IU. I test when there is a specific reason: bone loss, a gut condition that affects absorption, certain medications, or kidney disease. If you have been getting it checked every year with no reason attached, that is money you can keep.
Getting accurate results
- Fast 8 to 12 hours if I have ordered fasting glucose or insulin. Water and black coffee are fine unless I say otherwise.
- Stop biotin, which is in most hair, skin and nail supplements, two to three days before. It can throw off thyroid and some other tests.
- Skip hard workouts the day before. They can raise liver enzymes and creatinine temporarily and cause a scare over nothing.
- If you take creatine, tell me. It raises creatinine without meaning anything is wrong with your kidneys.
- Get labs at a similar time of day each time, so the results are comparable.
I wrote this for my patients, and it reads the same for everyone: general information, not a plan. If you would like your own numbers read against your own story, that is what a Lab Second Look is for. If you are not sure where to start, the free intro call is fifteen minutes.
A note on how to use this. General information for my patients, not individualized advice. Which labs you need depends on your history and goals.
- American Diabetes Association. Standards of Care in Diabetes—2026. Diabetes Care 2026;49(Suppl 1).
- Grundy SM et al. 2018 AHA/ACC guideline on the management of blood cholesterol. Circulation 2019;139(25):e1082–143.
- Koschinsky ML et al. 2024 NLA focused update on lipoprotein(a). J Clin Lipidol 2024;18(3).
- Ko CW et al. AGA guidelines on the gastrointestinal evaluation of iron deficiency anemia. Gastroenterology 2020;159(3):1085–94.
- Demay MB et al. Vitamin D for the prevention of disease. J Clin Endocrinol Metab 2024;109(8):1907–47.
Trang Ca Laube, FNP-BC, FMACP · Reclaim Power Telehealth · Updated September 2026
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