On a GLP-1? What to Test Before, During and After

GLP-1 medicines work. That is not in dispute. What is frequently missing is any laboratory picture of what else is changing while they do.

The numbers that should improve

• HbA1c — your average blood sugar over roughly three months.
• Triglycerides — usually the fastest-moving lipid.
• Total and LDL cholesterol — often improve, though less predictably.
• ALT — liver enzymes frequently fall as fatty liver improves.

A baseline before you start is what makes any of this readable. Without one, an improvement is a claim rather than a measurement.

The numbers that quietly fall

This is the part that gets missed. Rapid weight loss on a medicine that substantially reduces how much you eat carries a real nutritional cost, and the metabolic markers can look excellent while it happens.

• Albumin — a marker of protein status. Falling albumin during rapid loss is a signal worth acting on.
• Vitamin B12 — intake drops with appetite.
• Ferritin — iron stores follow the same path.
• Vitamin D — commonly low before treatment and rarely improved by it.

The organs to keep an eye on

• Creatinine and eGFR — kidney function, particularly if dehydration or vomiting has been part of the experience.
• ALT — liver, in both directions.
• TSH — thyroid, because unexplained weight change deserves a thyroid number regardless.
• C-peptide — how much insulin your body still makes on its own.

A sensible schedule

Baseline before the first dose. Repeat at about three months, which is roughly when HbA1c becomes meaningful again. Then every six months while you remain on treatment. If something changes sharply — persistent vomiting, severe abdominal pain, rapid unexplained loss — that is a conversation with your prescriber, not a test you order yourself.

We provide the laboratory work. Your prescriber provides the medicine and the plan.