Tirzepatide
A weekly injection that works on two appetite signals in the brain
Brand names: Zepbound / Mounjaro
Quick read · 5 min
People who tend to consider this:
- ✓Open to a weekly injection
- ✓Looking for the highest weight loss seen in trials
- ✓Comfortable with a higher monthly cost ($500–$1,100)
- ✓BMI 30+ or 27+ with health conditions
This may not be right if:
- ✕You have a personal or family history of medullary thyroid cancer
- ✕You have a history of pancreatitis
- ✕You are pregnant or planning to become pregnant
- ✕Your BMI is below 27 without qualifying health conditions
Not a complete list. Whether this treatment is right for you depends on factors only your doctor can assess.
Note: Prefer a pill? Semaglutide (Wegovy) is available as a daily pill for ~$149/month and shows similar weight loss in trials.
Weight loss — what trials show
In the largest clinical trial, people lost an average of about 20.9% of their body weight — roughly 46 lbs for a 220 lb person. Those who took a dummy pill lost about 2.4%. Results were consistent across multiple studies.
These are averages from clinical trials — individual results vary. Trials compare the drug against a dummy pill, not against other weight loss drugs.
See the full trial data →How this compares
Average weight loss in clinical trials. Not a ranking — individual results vary.
Averages from clinical trials at highest approved dose. Not everyone achieves these results.
What to expect — week by week
Many people notice reduced hunger or feeling full sooner. This varies between people.
Most people start to see measurable weight loss during this period.
Side effects often settle around this point. Measurable weight changes are becoming more visible.
This is when most of the weight loss typically happens. Side effects usually settle.
Rate of loss slows as your body approaches equilibrium.
What happens if you stop?
Most people who stop regain significant weight within a year. The chart below shows what the trial data found.
Weight trajectory — during treatment and after stopping
Based on: SURMOUNT-4 (2024)
Most of the lost weight returns within a year of stopping — this is the body returning to its defended weight, not a failure. Long-term use or maintenance therapy can help preserve results.
Side effects
Frequencies from SURMOUNT-1. Most stomach and gut side effects are mild-to-moderate and peak during the dose increase period (first 12–16 weeks).
Percentages from SURMOUNT-1. Source: trial publication.
- •In animal studies, tirzepatide caused thyroid tumours. It is unknown whether this applies to humans, but it is not prescribed to people with a personal or family history of medullary thyroid cancer.
- •Stop taking and contact your doctor immediately if you have persistent severe abdominal pain — this may be a sign of pancreatitis.
- •This drug may increase the risk of gallbladder problems. Tell your doctor if you develop sudden upper abdominal pain.
This is not a complete list. Your doctor can advise based on your full medical history.
Muscle and lean mass
In a body composition substudy of SURMOUNT-1 (n=160, DXA scans at 72 weeks), approximately 75% of weight lost was fat mass and 25% was lean mass — consistent with other weight loss interventions. Total lean mass change was –10.9% with tirzepatide vs. –2.6% with placebo.
What does the lost weight consist of?
Resistance training (weight lifting, bodyweight exercises) can significantly reduce the lean mass portion. Aim for 2–3 sessions per week during weight loss.
Source: SURMOUNT-1 body composition sub-study (DEXA scan)
Cost & access
~$1,086/month list price (LillyDirect savings programme: ~$650/month for eligible patients)
Requires a prescription from a licensed healthcare provider. Prices vary. Ask your doctor about savings programs.
~$500–$1100/moper month (list price)
Eli Lilly's LillyDirect savings programme may reduce cost to ~$650/month for eligible patients without insurance.
How to take it
- •Inject under the skin of your thigh, abdomen, or upper arm — once per week, on the same day each week
- •Starting dose is 2.5mg. Your doctor will increase it every 4 weeks — up to a maximum of 15mg
- •Store in the refrigerator (36–46°F). Can be kept at room temperature for up to 21 days if needed
- •Each pen is pre-filled and single-use — no dose preparation needed
How it works
A single molecule that activates two hunger-regulating signals in the brain — GIP and GLP-1 (both natural hormones released after eating). Activating both together produces greater appetite reduction and weight loss than activating either one alone.
Cardiovascular & other benefits
Improvements in systolic/diastolic blood pressure, triglycerides, LDL, and HbA1c across SURMOUNT trials. Reduced sleep apnoea severity (SURMOUNT-OSA). Reduced liver fat in NASH (SYNERGY-NASH phase 2). A dedicated cardiovascular outcomes trial (SURPASS-CVOT) is ongoing.
- ✓Reduced progression to type 2 diabetes
- ✓Improved sleep apnoea (SURMOUNT-OSA trial)
- ✓Reduced liver fat (SYNERGY-NASH phase 2 trial)
- ✓Improved triglycerides, blood pressure, and LDL cholesterol
Community insights
These are personal experiences shared in public online communities — not medical advice.
“Most people find the nausea is worst in the first 4–8 weeks during dose escalation. Eating smaller portions and avoiding fatty or spicy foods helps significantly.”
“Protein first at every meal — many users report it helps preserve muscle and keeps hunger controlled between doses.”
“The 'Zepbound plateau' is common around weeks 16–24. Many members report breaking through it by staying consistent and adjusting calories.”
Common questions
After reading this page, most people compare this with other medications, check if they qualify, or learn about side effects in more detail.
Next step most people take
Based on clinical trials · No rankings · Every claim linked to source
Last reviewed: March 2026