Weekly weight loss injections such as semaglutide (Wegovy) and tirzepatide (Zepbound/Mounjaro) have changed how doctors treat obesity. One of the most common questions is simple: how much weight will I actually lose?
The answer depends on the medicine, the dose, and your lifestyle. Here is what large clinical trials show, and what you can realistically expect.
How Weekly Weight Loss Injections Work
These medicines copy hormones your gut releases after eating. They help you feel full sooner, reduce hunger and food cravings, and slow how fast your stomach empties. Tirzepatide acts on two hormone pathways (GLP-1 and GIP), while semaglutide acts on one (GLP-1).
What the Clinical Trials Show
- Semaglutide 2.4 mg: In the STEP 1 trial, adults lost about 15% of their body weight on average over 68 weeks, alongside diet and exercise.
- Tirzepatide: In the SURMOUNT-1 trial, adults on the highest dose lost about 20% of their body weight on average over 72 weeks.
- Head to head: In the SURMOUNT-5 trial, people on tirzepatide lost more weight on average than those on semaglutide over 72 weeks.
These are averages. Some people lose much more, and some lose less.
A Typical Timeline
Doses usually start low and rise every 4 weeks to reduce side effects. Because of this, weight loss is slow at first.
- Months 1 to 2: Appetite drops, but weight loss is often modest while the dose is low.
- Months 3 to 6: Weight loss usually speeds up as you reach higher doses.
- Months 6 to 12: Many people continue losing weight, though more slowly.
- After about a year: Weight often levels off at a plateau.
What Affects Your Results
- Dose: Higher maintenance doses generally lead to more weight loss.
- Diet: Eating protein-rich, balanced meals helps protect muscle and improve results.
- Exercise: Strength training helps you keep muscle while losing fat.
- Health conditions: People with type 2 diabetes often lose a little less on average.
- Consistency: Missed doses and stopping early reduce results.
What Happens When You Stop?
Studies show many people regain much of the lost weight after stopping treatment, because appetite returns. Doctors often treat obesity as a long-term condition. Talk to your doctor before stopping or changing your dose.
For more on how these medicines work, read how semaglutide injections are changing weight loss.
Who Can Use Weight Loss Injections?
These medicines are prescription-only. They are usually prescribed for adults with obesity, or overweight adults with a weight-related health condition such as high blood pressure or type 2 diabetes. They are not suitable for everyone, including people with certain thyroid cancer histories and pregnant women.
Average Weight Loss by Month: A Realistic Example
Real-world results vary a lot, but here is a simple way to picture typical progress on weekly GLP-1 injections when combined with diet and activity:
- Month 1: low starting dose; appetite falls and weight loss is usually modest.
- Month 2: dose increases; many people notice clothes fitting more loosely.
- Months 3 to 4: weight loss often speeds up as the dose rises further.
- Months 5 to 6: many people have lost a meaningful share of their starting weight.
- Months 7 to 12: loss continues more slowly, often approaching a plateau.
In trials, average weight loss after about a year to a year and a half was around 15% of body weight with semaglutide 2.4 mg and around 20% with the highest dose of tirzepatide. For a person weighing 100 kg, 15% equals about 15 kg.
Why Some People Lose Less Weight
If your results are slower than expected, one of these factors may be involved:
- Still building up the dose: the full effect often takes several months.
- Eating high-calorie foods: smaller portions of fried, sugary, or processed foods can still add up.
- Drinking calories: juice, sweet coffee drinks, and alcohol are easy to overlook.
- Low activity: movement helps you burn energy and protect muscle.
- Poor sleep and stress: both can increase appetite and cravings.
- Medical conditions: hypothyroidism, PCOS, and type 2 diabetes can affect results.
- Other medicines: some antidepressants, steroids, and diabetes drugs can cause weight gain.
Talk to your doctor if you aren’t seeing progress after several months at a stable dose.
How to Get the Best Results
These habits can help you make the most of your treatment:
- Prioritise protein at every meal to stay full and protect muscle.
- Fill up on vegetables for fibre and nutrients.
- Drink water throughout the day.
- Do strength training two to three times a week.
- Walk daily, even for 20 to 30 minutes.
- Eat slowly and stop when you feel satisfied.
- Track progress with waist measurements and photos, not only the scale.
- Keep follow-up appointments so your doctor can adjust treatment.
Understanding a Weight Loss Plateau
Almost everyone reaches a point where the scale stops moving. This is a normal response: as you lose weight, your body needs less energy, and appetite hormones adjust.
To move past a plateau, review your portions, increase protein, add more strength training, and check in with your doctor about your dose. Sometimes a plateau simply means you’ve reached a healthy, stable weight for your body.
Weight Loss Is Not the Only Benefit
Losing even 5% to 10% of your body weight can bring real health improvements, such as:
- Lower blood pressure
- Better blood sugar control
- Improved cholesterol levels
- Less strain on knees and hips
- Better sleep and reduced snoring
- More energy for daily activities
Your doctor may track these health markers alongside your weight.
Safety Reminders
- Use only medicines prescribed by a licensed doctor and supplied by a registered pharmacy.
- Avoid unregulated online products sold as “semaglutide” or “tirzepatide” without a prescription.
- Never increase your dose faster than prescribed.
- Report severe stomach pain, persistent vomiting, or signs of dehydration straight away.
Frequently Asked Questions
Is it normal to lose weight slowly at first?
Yes. Doses start low and increase gradually, so the first one to two months often bring smaller changes.
How much weight can I lose in 3 months on injections?
It varies widely. Many people see steady progress by the third month as doses rise, but individual results depend on dose, diet, activity, and health conditions.
How much weight can I lose in the first month?
Many people lose a small amount in the first month, because doses start low. Results usually build over several months.
Which injection causes the most weight loss?
In trials, tirzepatide has produced more average weight loss than semaglutide. Your doctor will choose based on your health, cost, and availability.
Do I still need to diet and exercise?
Yes. The trials combined the medicines with diet and activity. Healthy habits also help you keep weight off.
Disclaimer: This article is for general information only and is not a substitute for professional medical advice. Always consult a qualified doctor about your health.
