Guide//5 min
Constipation on a GLP-1
Nausea gets the attention because it arrives first and loudly. Constipation arrives in week three, never fully resolves for some people, and is the thing they eventually stop over.
Medications
Mounjaro
Tirzepatide, the dual GIP/GLP-1 agonist.
21 pieces
Guide//5 min
Teeth and dental work
Repeated vomiting erodes enamel permanently, reflux does it more quietly, and any dental procedure involving sedation now needs the same conversation as surgery. None of this is on the leaflet.
Guide//5 min
Diarrhoea on a GLP-1
A drug famous for slowing the gut down produces loose stools in a substantial minority, which sounds contradictory until you know what else is usually in the picture.
Explainer//6 min
A1c on a GLP-1
Roughly one and a half to two points for semaglutide, and more than two for tirzepatide. The more interesting question is why the number lags a month behind everything you are doing.
Guide//5 min
GLP-1s before surgery
In 2023 the advice was to hold your weekly injection for a week. In 2024 a multi-society panel replaced that with something considerably more nuanced. Plenty of pre-op letters have not caught up.
Guide//6 min
GLP-1 dose charts, side by side
Four drugs, four different ladders, and a great deal of confusion about which rung anyone is standing on. Here is every approved escalation schedule in one place, with the reasoning behind the steps.
Explainer//5 min
GLP-1 drug interactions
These drugs are not metabolised by the liver enzymes that cause most interactions, so the usual list is almost empty. What replaces it is a single mechanical problem: everything you swallow now arrives late.
Explainer//5 min
Every GLP-1 medication
There are more of these than the two everyone talks about, several are considerably older, and a few are still widely prescribed for reasons that have nothing to do with weight.
Guide//5 min
GLP-1 pen problems
Almost every device problem people describe turns out to be one of six things, and the one that matters most is knowing when you have actually missed a dose.
Guide//5 min
Sulfur burps on a GLP-1
The rotten-egg burp is one of the most reliably reported side effects on tirzepatide and one of the least discussed in clinic, largely because nobody wants to be the person raising it.
Guide//5 min
Switching between GLP-1s
The most common error when moving from semaglutide to tirzepatide is assuming your current dose buys you a head start. It does not, and the week you find that out is memorable.
Explainer//5 min
The thyroid cancer warning
Every box in this class carries a boxed warning about thyroid tumours in rodents. Fifteen years of human data have not confirmed it, and the warning is still there — for reasons worth understanding.
Explainer//5 min
Tirzepatide, explained
Eli Lilly added a second hormone receptor to the design, largely as a bet. It produced the largest average weight loss of any approved drug, and nobody can yet fully explain why.
Guide//5 min
Travelling with your GLP-1 pen
The pens are more robust than people fear and less robust than a hot car boot. Most travel problems come down to three numbers and one decision about which bag it goes in.
Guide//5 min
Where to inject your GLP-1
Abdomen, thigh or upper arm, and it genuinely does not matter which. What matters is the handful of things people do wrong in the ten seconds before the needle goes in.
Guide//2 min
Best supplements on tirzepatide
Tirzepatide takes off more weight than any injectable before it, and the supplement question changes with the magnitude. When a fifth of your body is leaving, what you protect matters more than what you optimise.
News//3 min
The head-to-head trial, and what it settles
For three years the comparison between semaglutide and tirzepatide was made by holding two separate trials side by side, which is not a comparison. A direct trial changed that — and the result matters less to your decision than you would think.
Guide//5 min
Missing a dose of Mounjaro or Zepbound
The four-day rule, the reason it exists, and why the fix that feels most sensible — doubling up — is the one that puts people in the emergency department.
Deep Dive//5 min
Zepbound, sleep apnea, and the coverage door it opened
When Zepbound was approved for obstructive sleep apnea, it stopped being a weight-loss drug in the eyes of a large part of the American payment system. That distinction is worth thousands of dollars a year to some people.
News//4 min
Contraception, pregnancy, and the four-week rule
Tirzepatide can reduce the effectiveness of oral contraceptives — after the first dose and after every increase. It is printed on the label, it is rarely mentioned in the appointment, and it has a specific four-week window attached to it.
Explainer//3 min
Semaglutide or tirzepatide
One is a GLP-1 agonist. The other adds GIP. The trial data favor one of them on weight — which is not the same as saying it is the right one for you.
Also in Medications
On The Jab
The
GLP‑1
Handbook
Dr. Nick Robertson
MD
The book · 14 chapters
The GLP-1 Handbook
Everything I tell my own patients before their first injection. 214 pages of what actually matters in the first year — dosing, side effects, food, muscle, cost, and the part nobody prepares you for: maintenance.
$4Less than your morning coffee.
Priced at four dollars because it should be affordable to everyone taking these drugs — not because it's worth four dollars. No upsell, no course, no supplement line.