Collecting this in one place because it comes up every few weeks and the answer is always assembled from scratch. It is about the baseline and follow-up panel, and it is deliberately narrow — everything I am not confident about is marked as such.
What is actually established
A defensible baseline is short: HbA1c and fasting glucose, a lipid panel with ApoB if you can get it, ALT and AST, creatinine with eGFR, TSH, ferritin and B12, and a full blood count. That set catches the things that change, the things that explain symptoms, and the things that alter the prescribing decision. Almost everything else on the long circulating lists is either invariant, uninterpretable without a specific question, or an incidental finding waiting to cause an unnecessary workup.
The condition it depends on
One addition: if the lab changes analytical platform between your draws, the comparison breaks and nobody tells you. It is worth asking when a value moves inexplicably.
The practical version
Post reference ranges alongside numbers when you share them. Units differ by country — glucose and lipids especially — and half the confusion in these threads is unit mismatch rather than disagreement.
What I am not sure about
The question I want answered is how often to repeat it, because quarterly seems to be the convention and I cannot find the reasoning. If the honest answer is that nobody knows, that is a useful answer and I would rather have it.
— CryptoCarl · corrections welcome and will be edited into this post with credit