Tirzepatide
Brand names: Zepbound / Mounjaro
Quick read · 5 min
Tirzepatide (Zepbound / Mounjaro) is a weekly injection that showed the highest average weight loss of any approved medication — up to 20.9% in clinical trials, or about 46 lbs for a 220 lb person.
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.
Prefer a pill? Semaglutide (Wegovy) is available as a daily pill for ~$149/month and shows similar weight loss in trials.
Not sure where to start? Our 2-minute quiz can help.
Take the quiz →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.
About 1 in 10 people in trials did not respond significantly to treatment. If you have been on treatment for 12–16 weeks without meaningful weight loss, it is worth discussing this with your doctor.
In the head-to-head SURMOUNT-5 trial (NEJM, May 2025), tirzepatide produced 20.2% average weight loss compared to 13.7% for semaglutide — under the same conditions, in the same trial.
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.
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
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 is “food noise”?
Many people notice the constant background thoughts about food begin to quiet down — what researchers and patients call "food noise" starting to fade. This is one of the most commonly described early effects. Not everyone experiences this to the same degree.
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.
Side effects are most common during the first 4–8 weeks when doses are being increased. For most people, they settle significantly after that.
Hair thinning
Some people notice hair thinning or increased shedding around months 3–6 of treatment. This is usually caused by the physical stress of rapid weight loss on the body — a temporary condition called telogen effluvium — rather than the medication itself. In most cases, hair regrows on its own within 6–12 months. If hair loss is severe or persistent, speak to your doctor.
What happens if you stop?
Most people who stop regain significant weight within a year. The chart below shows what the trial data found.
What happens when you stop
Source: SURMOUNT-4 (2024)
medication
after stopping
after 1 year
In clinical trials, participants regained about 67% of the weight they lost within a year of stopping. This is the body returning to its defended weight — not a personal failure. Current evidence supports long-term use for people who respond well.
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)
Resistance training and high-protein intake are the two most evidence-based ways to protect lean mass during medicated weight loss.
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.
Common questions
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.
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 patterns people report
From public online communities — not medical evidence.
- •Food noise fading is the most commonly described distinctive early effect — often reported before significant weight loss begins
- •Nausea common first month, manageable by month 2–3
- •Some report more energy, others fatigue during dose-increase phase
- •Weight loss pace varies week-to-week and month-to-month
How people tend to think about this option
- —This option shows the highest average weight loss in clinical trials compared to other approved medications.
- —Side effects are most common in the early weeks and settle for most people over time.
- —Clinical guidelines generally position this after lifestyle approaches have not produced sufficient weight loss.
- —It typically requires ongoing use — most trials show weight returns after stopping.
These are common considerations — not recommendations. Your doctor can help assess which factors matter most for your situation.
Deep dives
Dedicated pages on how to take it, dosage, side effects, and cost.
Week-by-week experience, the 12-month journey arc, and practical tips for starting
Full step-by-step guide, storage, missed doses
Available doses, dose-response, maintenance
Step-up timeline from starting dose to maintenance
Full list with frequencies, warnings, and management
Contraindications, cautions, and drug interactions
List prices, savings programs, insurance reality
Month-by-month results at 1, 3, 6, and 12 months in real pounds
Fridge rules, room temp window, travel, damaged pens
Alcohol, metformin, thyroid, BP drugs, NSAIDs, and more
Protein targets, meal ideas, and the eating-too-little trap
The 4-day window and when to skip
Where to inject, rotation schedule, and troubleshooting lumps
Same active ingredient, same max dose — here's what's actually different
Related comparisons
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: April 2026