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Is HbA1c worth drawing at baseline before starting tirzepatide?

Asked 8 Mar 2026Modified 28 days agoViewed 12k times
21

Conditions: HbA1c · tirzepatide.

I want to decide this in advance so that I am not deciding it under pressure later.

Assume I will follow the plan I write down, so I would like it to be a good one.

What would you do, and what would make you change course?

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askedh_villanueva70k488 Mar 2026
6Was this fasting, and for how long? Several of these move with the last meal. – low_dead_space 7 months ago
7Do you have a baseline from before you started, or is this the first panel? – Dr_Nadia_Farsi 8 months ago
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2 Answers

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Accepted answer

This is answerable, and the answer is mostly about which tests rather than how many.

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.

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.

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 2 Jul 2026 by wren_calloway — added a caveat about sampling

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answered · acceptedwren_calloway23k3810 Jun 2026
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Standardise the conditions — same time of day, same fasting state, same laboratory — or you are measuring the conditions rather than yourself.

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.

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.

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.

edited 2 Jul 2026 by ben_akintola — corrected a unit error in the worked example

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answeredben_akintola10k1621 Jun 2026

Your answer

Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.

Not medical advice. Research-use-only compounds are not approved for human use.