Where this comes from

I would rather you check than take my word for it.

This book is written for patients, so I have kept citations out of the text itself — nobody should have to read around footnotes to find out whether their nausea is normal. But every number in it comes from somewhere, and if you want to read the primary sources yourself, here they are.

The official prescribing information

These are the documents the FDA approves alongside the medication. They contain the boxed warning, the full list of side effects with the rates seen in clinical trials, the dosing schedule, and the contraindications. They are dense, but they are the source of record — and most of the specific numbers in Chapters 2 and 4 come from them.

• Zepbound (tirzepatide) prescribing information — Eli Lilly
• Wegovy (semaglutide) prescribing information — Novo Nordisk

On compounded medications

Chapter 5 describes the FDA's documented concerns with compounded GLP-1 products, including dosing errors and unapproved salt forms. These are the FDA's own statements.

• FDA's concerns with unapproved GLP-1 drugs used for weight loss
• FDA alert on dosing errors with compounded injectable semaglutide
• FDA guidance for compounders as GLP-1 supply stabilized

On monitoring, muscle loss, and the research

The muscle-loss figure in Chapter 3, the monitoring schedule in Chapter 6, the contraception interaction in Chapter 4, and the Scandinavian thyroid cancer data draw on the clinical reference literature that physicians use — principally UpToDate's guidance on monitoring patients taking GLP-1-based medications, and the studies it reviews. Access to that reference requires a subscription, which most patients do not have and should not need. Your own physician can look up any of it with you.

A word about how to read any of this

Two things are worth knowing before you go looking.

Studies that follow large groups of people can show that two things occur together without showing that one caused the other. You will see this a great deal in coverage of these medications, and it is the single most common way a headline overstates its evidence.

And the rate of a side effect only means something next to the rate in people who took a placebo. A number on its own — "25 percent experienced nausea" — is not interpretable without it.

This page lists sources, not medical advice. Nothing here replaces a conversation with your own physician.