Is eGFR worth drawing at baseline before starting orforglipron?

For reference: eGFR · orforglipron.

This is a planning question. I know what my options are; I do not know how to weigh them.

What I want is the minimum viable version, which I suspect is smaller than what I would design.

What does a sensible plan look like, and what are the decision points?

The short version: a small, well-chosen panel with a baseline beats a large one without.

A twenty-analyte panel run on a healthy person will produce, on average, one out-of-range result purely from how reference intervals are constructed. That is arithmetic rather than pathology.

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.

External quality assurance schemes document between-laboratory differences on common analytes that routinely exceed the size of clinically interesting changes.

The caveat is that a panel is not a diagnosis and interpreting one is a clinician's job, particularly when several values move together.

Decide the action for each result before you order the test.

Start with a baseline. A result taken before anything started converts most later ambiguity into a simple comparison, and it cannot be obtained retrospectively.

Keep the reports rather than the numbers. Units, reference intervals and methods all vary, and a bare number two years later is not comparable to anything.

Timing matters per analyte: cortisol and testosterone are diurnal, triglycerides are postprandial, and creatinine responds to hydration and to recent training. Fixing the conditions removes most of the noise.

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.

Research-use compounds are not approved for human use, and no panel makes that safer.

Same laboratory, same time, same fasting state, or the comparison is not a comparison.

edited 31 Jul 2025 by swab_and_wait — updated for the 2026 guidance change

The honest position is that most people order too many analytes and too few time points, when the reverse would be more informative.

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.

Pre-analytical factors — posture, tourniquet time, fasting, sample handling — are the largest source of error in routine biochemistry, well ahead of the analysis itself.

Ordering tests you will not act on generates anxiety and incidental findings, both of which have costs.

One out-of-range value on a twenty-analyte panel is expected. Two on a repeat is a finding.

Before reacting to any single value, check whether it is outside the interval by an amount larger than the assay's own variation.

Haemolysis in the sample raises potassium and several enzymes spuriously. If a result is bizarre, ask whether the sample was flagged before building a theory on it.

SELECT reported a hazard ratio of 0.80 (95% CI 0.72–0.90) for the primary composite major adverse cardiovascular event endpoint with semaglutide 2.4 mg in overweight or obese adults with established cardiovascular disease and without diabetes[1].

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.

Keep the full report, not the number. You will need the units and the interval later.