Taking the question as asked, rather than the general version of it. Quarterly for the first year is convention rather than evidence, and it is defensible for a simple reason: it is roughly the interval over which HbA1c becomes informative again, since it reflects about three months of glycaemia. After the first year, and once doses are stable, annual is reasonable unless something specific is being followed.

BenResearch_OR said:

Quarterly for the first year is convention rather than evidence, and it is defensible for a simple reason: it is roughly the interval over which HbA1c…

That is correct as far as it goes, and here is where it stops going. 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.

DataDave said:

My prescriber ordered three tests and this board recommends about twenty, and I would like to know which of those two lists is right.

Same position here, arrived at the long way round. 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.

Correct me if the detail matters more than I have assumed.

Adding the clinical framing, because it changes how the question reads.

PSA: get baseline labs BEFORE starting baseline bloodwork therapy. You need a "before" picture to measure progress. My recommended pre-treatment panel:

1. CMP + A1C + fasting insulin
2. Complete lipid panel with particle count if possible
3. hsCRP, ferritin, B12, vitamin D
4. Thyroid panel (TSH + free T4)
5. CBC with differential
6. Liver panel (ALT, AST, GGT)
7. DEXA scan or body composition

Total cost at Quest without insurance: ~$200. Worth every penny for the data.