Is My Weight-Loss Medication Working? How We Judge Response
In this article
In brief
- Medicines such as Wegovy and Mounjaro are increased step by step, and the full dose typically takes 16 to 20 weeks to reach.
- A slow start does not predict a poor result: in a trial analysis, most “late responders” reached 5% loss with continued treatment.
- We judge response after around four months on your full dose, looking for at least 5% loss of starting weight.
- Waist, blood pressure, HbA1c, liver enzymes and lipids often improve before the scale moves much.
We review weight medication at our Punggol clinic, whether you started it with us or elsewhere. See our weight management programme.
The question every patient asks by month two
“I’ve been injecting for eight weeks and I’ve only lost two kilos. Is it working?”
At eight weeks, we usually can’t tell yet, and that’s not a failure of the medication or of you.
Why the first months understate the medication
Semaglutide (Wegovy) and tirzepatide (Mounjaro) are titrated. The dose rises gradually, usually every four weeks, so your body can adjust and side effects stay manageable. The full therapeutic dose typically takes 16 to 20 weeks (four to five months) to reach.
Until then, you are not on the dose the clinical trials tested. Judging the medicine in month two is like judging a marathon at the 5-kilometre mark.
What the evidence says about “slow starters”
An older rule of thumb, still quoted online, says to stop if you haven’t lost 5% of your body weight within 12 weeks. It was written in 2015, before the current medicines existed.
In a 2025 analysis of the SURMOUNT-1 trial, about one in five people on tirzepatide were “late responders”, with under 5% loss at week 12. With continued treatment, around 70% of them reached 5% loss by week 24, and roughly 90% by week 72. Similar patterns have been seen with semaglutide.
A slow start does not predict a poor result.
How we judge response at KTMC
- During titration (months 1–4): the goals are tolerability and adherence, not a weight target. We track your weight and waist at each visit, manage side effects and adjust the pace to you.
- At maximal tolerated dose: after around four months on your full (or highest comfortable) dose, we check formally whether you have lost at least 5% of your starting body weight.
- If yes, you’re a responder. We continue and discuss a realistic further trajectory. Many patients reach 10–15% or more.
- If no, we act rather than drift. First we check adherence and injection technique. Then we review the dose or medicine; some patients respond to tirzepatide after minimal response to semaglutide, and vice versa. We revisit lifestyle and, where appropriate, discuss whether a bariatric surgical opinion would serve you better than another six months of medication.
Weight is not the only measure. Waist, blood pressure, blood sugar (HbA1c), liver enzymes and lipids often improve before the scale moves much. We track them at baseline, month 3 and month 6, and they count.
What this means in practice
- Don’t stop on your own at week 8 or 10. The dose you’re on isn’t the dose being judged.
- Keep the monthly reviews. Titration is how the medicine works, and skipped reviews are the most common reason for a flat response.
- Expect the formal verdict around months 5 to 8, depending on your titration.
- A properly identified non-response is useful. It tells us to change something, not that nothing can be done.
Unsure whether your weight medicine is working? A structured review can answer that, whether you started it with us or elsewhere.
Get in touch
Punggol — 658 Punggol East, #01-04, Singapore 820658 · Tel 6312 4589
Joo Chiat — 172 Joo Chiat Road, #01-01, Singapore 427443 · Tel 6920 1952
Email — admin@ktmc.sg
References
- Ard J, et al. Weight reduction over time in tirzepatide-treated participants by early weight loss response: post hoc analysis of SURMOUNT-1. Diabetes Obes Metab. 2025;27:5064–5071.
- Real-world titration, persistence and weight loss of semaglutide and tirzepatide in an academic obesity clinic. Diabetes Obes Metab. 2025.
- Real-world weight loss with semaglutide and tirzepatide in patients with overweight or obesity without type 2 diabetes (SHAPE). Adv Ther. 2025.
This information is for general education only and is not a substitute for medical advice. Please see a doctor for advice about your own situation. v1.1 · October 2026 · Review due October 2028.