What Happens in the First Week of GLP-1 Therapy

The first week surprises most people, usually not because of side effects but because of a change they did not expect. This page covers what commonly happens and what you should be recording. Technique and storage are explained in person at the clinic rather than on a website, because they depend on what is prescribed.

Days one to three

The starting dose is deliberately low. For most people the first change is not fullness but the disappearance of repetitive thoughts about food. Midday arrives and you notice you have not thought about eating yet. Some feel mild nausea or heaviness on day two or three, particularly after oily meals.

Days four to seven

Portions start feeling too large before you finish them. This is the part most often handled badly. Keep eating to the end out of habit and you get hours of heaviness. Stop early without changing what is on the plate and protein is the first thing to fall. Two things need changing this week: the order on the plate, and how fast you eat.

What does not happen in the first week

Weight usually does not move much, and if it moves fast most of it is water. The starting dose is not the effective dose. It is the dose the body adjusts to. People who judge the whole decision on day seven usually reach the wrong conclusion, in either direction.

What you should be recording

• Weight at the same time of day, not every day
• Actual grams of protein eaten, on at least three days that week
• Nausea and heaviness: when it happened and after which meal
• Bowel frequency and fluid intake
• Evening energy and sleep quality

Those notes are what decide whether the dose goes up, is held, or whether the eating pattern needs fixing first.

Three common first-week mistakes

First, cutting calories as far as possible because appetite has gone. That is the most common cause of early fatigue and muscle loss. Second, forgetting fluid and fibre, so constipation starts in week two. Third, stopping training because energy feels lower, when resistance training is the thing protecting muscle while weight comes down.

When to contact the clinic in the first week

Severe, persistent abdominal pain, vomiting to the point of not keeping fluids down, pain under the right ribs, yellowing of the skin or eyes, or signs of an allergic reaction such as facial swelling and difficulty breathing. The full list is in GLP-1 side effects. For how to arrange meals in the first week, see nutrition on GLP-1 therapy, and for the mechanism see how GLP-1 therapy works. The baseline measured before starting is covered in the metabolic assessment and body composition test. Book a consultation for an assessment.

For the full picture of the doctor-led programme and where GLP-1 therapy fits, see doctor-led GLP-1 and weight management.

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Every iLIV guide is written and reviewed under our editorial standards, and each one carries the name of the reviewing doctor together with their MMC registration number.

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