Accepted answer
The short version: a small, well-chosen panel with a baseline beats a large one without.
Same laboratory, same method, same time of day, same fasting state. Between-laboratory differences on several common analytes are larger than the changes people are trying to detect.
Headline results, principal programmes
| Trial | Agent | n | Duration | Primary result |
|---|
| STEP 1 | Semaglutide 2.4 mg | 1,961 | 68 wk | −14.9 % vs −2.4 % weight |
| STEP 2 | Semaglutide 2.4 mg, T2DM | 1,210 | 68 wk | −9.6 % vs −3.4 % weight |
| SURMOUNT-1 | Tirzepatide 5/10/15 mg | 2,539 | 72 wk | −15 / −19 / −21 % weight |
| SURMOUNT-4 | Tirzepatide, withdrawal | 670 | 88 wk | Continued loss vs substantial regain |
| SELECT | Semaglutide 2.4 mg | 17,604 | ~40 mo | MACE HR 0.80 (0.72–0.90) |
| FLOW | Semaglutide 1.0 mg, CKD | 3,533 | ~3.4 yr | Renal composite reduced; stopped early |
| SURMOUNT-OSA | Tirzepatide, OSA | 469 | 52 wk | AHI reduced with and without PAP |
Delta checks — comparing against your own previous value — are far more sensitive than comparing against a population interval, which is the argument for keeping a series rather than a snapshot.
Biological variation data are published per analyte and are the basis for the reference change value — the difference between two results that is larger than noise.
Nothing here is medical advice. If something is out of range and you do not know why, that is a consultation rather than a research project.
Decide the action for each result before you order the test.
edited 7 Jul 2025 by sian_llewellyn — added a caveat about sampling
4Minor: haemolysis inflates potassium enough to cause a fright over what is a handling artefact. – orla_sheridan 5 months ago 3Thank you — this is the answer I was looking for. – orla_ferriter 3 months ago add a comment