The question is nearly always asked in week two, which is the worst possible week to be forming a judgement.
Almost everything people experience early on this drug class is temporary, and knowing roughly how temporary changes whether they get to month six. A very small number of things are not temporary, and those are worth separating out clearly.
The shape of the whole thing
For the full directory ordered by how likely each effect actually is, see every side effect ranked.
Every symptom in this class follows the same curve, and once you can see the curve the individual weeks stop being alarming.
A dose increase lands. Symptoms rise over two to four days. They peak, then decline over one to two weeks. By week three at that dose most people feel close to normal. Four weeks in, the next step arrives and the cycle repeats — but each cycle is usually milder than the last, because the underlying adaptation is cumulative.
The exception is the very first dose, which for many people is the sharpest transition of the whole programme simply because nothing has adapted yet.
Days 1–3
When post-injection nausea typically peaks after each dose
4–8 weeks
Time for symptoms to settle substantially at a stable dose
Week 4
The recurring hard week — a new dose arriving at the low point of the last one
By symptom
Nausea. Onset within days of the first injection. Peaks one to three days after each dose. Substantially settled by four to eight weeks at a stable dose. The most reliably temporary thing on this list. What to do about it in the meantime is in is this nausea normal, and the supplement options are compared in supplements for GLP-1 nausea.
Vomiting. Less common than nausea, similar timeline. Vomiting that persists beyond a few days, or prevents fluids, is not part of the normal pattern.
Diarrhoea. Less common than constipation and usually caused by something other than the injection — see diarrhoea on a GLP-1.
Constipation. Starts around week two to three. Frequently does not fully resolve, and returns with each dose increase. This is the one to build a standing routine for rather than wait out — see constipation on a GLP-1.
Reflux and heartburn. Builds over the first month, worse at night, and usually improves as the gut adapts and weight comes off. Mechanical fixes in reflux on a GLP-1.
Sulfur burps. Characteristically tirzepatide, typically week two to four after a step up, usually gone by week eight. See sulfur burps.
Fatigue. Common in the first six to eight weeks and usually a consequence of eating far less rather than a direct drug effect. Persistent fatigue past that window deserves blood tests — see supplements for GLP-1 fatigue.
Injection site reactions. Days. Mostly technique — where and how to inject.
Hair shedding. The outlier in timing. Typically begins two to four months after the fastest phase of weight loss, not during it, and resolves over a further three to six months. Explained in does Ozempic cause hair loss.
Facial volume loss. Not a side effect in the pharmacological sense and not temporary — it tracks weight loss and skin retraction over six to twelve months. See Ozempic face explained.
Taste changes and food aversions. Weeks to months, and usually a shifting target rather than a fixed one.
What to do when a step is intolerable
The single most useful intervention in this whole area is also the least used: stay where you are for longer.
The four-week interval is a minimum, not a schedule. Extending a step to six, eight or ten weeks is entirely ordinary practice, costs you very little in the long run, and resolves the majority of tolerance problems. Stepping back down one level and re-climbing more slowly works too.
The evidence that slower titration reduces discontinuation is considerably better than the evidence for any particular anti-nausea remedy — which is worth remembering before you spend money on remedies. The ladders and intervals are in the dose charts.
Almost nobody needs to stop this medication. A great many people need to spend eight weeks at a dose instead of four.
The discontinuation numbers
Worth some proportion. In STEP 1 and SURMOUNT-1, discontinuation due to gastrointestinal adverse events ran in the low single-digit percentages — meaning the overwhelming majority of people who started, and had side effects, continued.
That is not a reason to dismiss anyone’s experience. It is a reason to be sceptical of the assumption, common at week two, that you are the exception.
The ones that are not just side effects
A short list, because the timeline above does not apply to any of them.
The week that decides it
If there is one thing worth taking from this page, it is that week four of the first month is where most people quit — and it is the least representative week of the entire year.
The scale has barely moved, the starting dose was never meant to produce weight loss, and a new dose has just arrived bringing a fresh round of nausea. Everything about that week argues for stopping, and almost everything about it is temporary. The month-by-month version is in the first eight weeks, how long Wegovy takes to work, and — for what is worth taking through it — supplements for your first month.
The summary you can hold onto
Two weeks bad, then better. Repeat at each step, milder each time. Mostly settled by month three.
Constipation stays and needs managing. Hair sheds later and grows back. Everything on the red-flag list is a phone call rather than a waiting game.