Getting started
Your first four weeks on a GLP-1
Nobody tells you what the first month actually feels like. Here is the shape of it, so less of it comes as a surprise.
Before your first injection
Set your baseline
You only get one chance to record where you started. Take a weight, a set of measurements and a photo, even if you would rather not look at them. Months from now, when the scale is being stubborn, those are the things that prove the scale is not the whole story.
- Weigh yourself once, at a time you can repeat: morning, after the loo, before eating.
- Measure your waist. It often moves when weight does not.
- Note what you eat in a normal week. Not to judge it, just so you can see what changes.
Week 1
The quiet
The change most people notice first is not in their body but in their head. The constant background negotiation about food, often called food noise, gets quieter. Some people find this wonderful and some find it unsettling. Both are normal.
Physically, expect less than you might hope for and more than you might fear. Appetite drops. Meals you used to finish become too much. Nausea, if it comes, usually starts in the first few days and is worst in the first 24 to 72 hours after the injection.
What helps
- Eat smaller and earlier. Half your usual portion, stopping before full, beats a normal plate you then regret.
- Go plain and low fat when queasy. Greasy, fried and very rich food is the most commonly reported trigger.
- Drink before you are thirsty. Thirst cues fade along with hunger cues, and a lot of early-week headaches and fatigue are simple dehydration.
Week 2
Settling, and the first plateau scare
Week one often shows a drop of several pounds. Much of that is water and the contents of your gut, not fat, and week two frequently shows almost nothing. This is the point at which a lot of people conclude the medication has stopped working. It has not. Two weeks is not a trend.
Digestion is the theme of week two. Everything moves more slowly on a GLP-1, which is part of how it works, and constipation is one of the most common complaints. Fluid, fibre and movement are more effective than waiting it out.
Weeks 3 and 4
Protecting what you keep
By now eating less is easy, which introduces the real risk of the first month: losing weight you did not want to lose. When intake drops sharply, the body takes some of the difference from muscle unless you give it a reason not to.
Two things prevent most of that, and neither is complicated.
- Protein first, every meal. A common target is roughly 1.2 to 1.5 g per kg of body weight per day. On a small appetite that means protein goes on the fork before anything else does.
- Resistance work twice a week. Bodyweight at home counts. This is the single best-evidenced way to hold on to muscle while losing fat.
Somewhere around here you will also meet your first dose increase. Expect the early-week side effects to return for a few days after each step up. Later steps are often easier than the first.
What is worth tracking, and what is not
| Worth tracking | Why |
|---|---|
| Protein, daily | The one number that most affects how you come out of this. |
| Fluid, daily | Thirst cues are unreliable now. Most early side effects get better with more. |
| Injection day and site | Rotating sites protects your skin, and knowing your day explains your week. |
| Side effects, briefly | Patterns are what your prescriber can actually act on. |
| Weight, weekly | Weekly. Daily weighing on a GLP-1 mostly measures water. |
Not worth tracking in month one: your rate of loss compared with anyone else's. Starting weight, dose, sex, age and starting muscle all change the number, and comparison at this stage is only ever a way of feeling bad.
Worth a call to your prescriber, without waiting
- Severe stomach or abdominal pain that does not ease, especially if it goes through to your back, with or without vomiting.
- Vomiting you cannot stop, or being unable to keep fluids down for around a day.
- Signs of dehydration: very dark urine, passing much less than usual, dizziness on standing.
- Anything that frightens you. Being wrong and reassured is a fine outcome.
Never change, skip or double a dose to manage side effects. Adjusting a schedule or holding at a lower dose for longer is a routine decision for your prescriber and a risky one to make alone.
A free guide from Sated · satedglp1.com/guides
General information, not medical advice, and no substitute for the team who prescribed your medication. Always follow the patient information leaflet that came with your pen and the instructions you were given. Last reviewed August 2026.