Is GGT worth drawing at baseline before starting liraglutide?

Setup, so nobody has to ask: GGT · liraglutide.

The failure mode I am trying to avoid is making this decision emotionally.

I have twelve months in view and I would like the plan to survive that long.

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

The relevant statistical point is that a ninety-five per cent reference interval means one analyte in twenty will read out of range in a healthy person by construction.

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.

Headline results, principal programmes

Repeat before you react. A single abnormal value has a substantial probability of being within the combined biological and analytical variation of a normal one.

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

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

edited 29 Sept 2025 by Dr_Rosalind_Achebe — fixed an arithmetic slip in the third paragraph

Answer first: decide what you would do differently for each possible result before you order the panel. Anything that fails that test is a number you will worry about and not act on.

A sensible core for this population is a full blood count, renal function with electrolytes, liver enzymes with bilirubin, a fasting lipid panel with apolipoprotein B, HbA1c and thyroid-stimulating hormone.

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.

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.

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

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

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.

The underlying point is that 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.

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

Baseline first, then a repeat under identical conditions. Everything else is secondary.

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

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.

Reference intervals are conventionally the central ninety-five per cent of a reference population, which is the direct cause of the one-in-twenty out-of-range rate on a healthy panel.

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

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

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.

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.