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Tirzepatide37 residuesYEGTFTSDYSILDKIAQKAFVQWLIAGGPSSGAPPPSEach bubble = one amino acid. Size = residue mass. Color = chemical class.Also known as: LY3298176, Mounjaro, Zepbound
22.5% mean body weight reduction at 72 weeks on the highest dose. Tirzepatide (Mounjaro, Zepbound, CAS 2023788-19-2) is an FDA-approved dual GIP/GLP-1 receptor agonist, the first drug in its class to target both incretin hormones at once. In the SURMOUNT-5 head-to-head trial, it beat semaglutide 2.4 mg by nearly seven percentage points for total weight lost. The black box warning for thyroid C-cell tumors (rodent data, human relevance unknown) stays on the label. Obesity medicine physicians, type 2 diabetes patients, and adults who plateaued on semaglutide are the primary users.
20.2% body weight gone at 72 weeks, and that was the average, not the ceiling. Tirzepatide (LY3298176, CAS 2023788-19-2) is a 39-amino acid acylated lipopeptide sold as Zepbound for obesity and Mounjaro for type 2 diabetes. It activates both glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptors simultaneously. The dual receptor mechanism separates tirzepatide from single-target GLP-1 drugs like semaglutide. GIP receptor activation improves fat metabolism and may reduce the nausea burden that limits GLP-1-only treatment. GLP-1 receptor activation suppresses appetite, slows gastric emptying, and boosts insulin secretion. Those two pathways working together produce weight loss and glycemic control that neither achieves alone. SURMOUNT-1 (n=2,539)[1] showed dose-dependent results at 72 weeks: 15.0% weight loss at 5 mg, 19.5% at 10 mg, and 22.5% at 15 mg. SURMOUNT-5 (n=751)[2] ran a direct comparison; tirzepatide reached 20.2% versus semaglutide's 13.7%. Roughly one in five tirzepatide patients lost 30% or more of their body weight. The r/Zepbound community (180,000+ members) confirms what the trials found. Appetite suppression starts within days. Most users stabilize at 7.5 to 12.5 mg rather than pushing to the maximum 15 mg dose. Cost and insurance coverage remain the biggest barriers. Weight regain after stopping is well-documented; about two-thirds of lost weight returns within a year of discontinuation.
Tirzepatide binds to two separate incretin receptors on the same molecule. At the GIP receptor, its affinity matches native GIP closely. At the GLP-1 receptor, affinity is roughly 18 to 20-fold lower, making it what researchers call an "imbalanced" agonist that leans toward GIP-mediated pathways. GLP-1 receptor activation does the heavy lifting on appetite. GLP-1 activation suppresses hunger signaling in the hypothalamus, slows gastric emptying so food stays in the stomach longer, and triggers glucose-dependent insulin release from pancreatic beta cells. These effects explain the "food noise" silencing that users describe within days of their first injection. GIP receptor activation adds a second layer. GIP activation improves insulin sensitivity, increases adiponectin (a fat-tissue hormone linked to metabolic health), and appears to improve beta-cell function over time. The GIP component may also explain why tirzepatide causes less nausea than pure GLP-1 agonists; SURMOUNT-5 recorded a GI discontinuation rate of just 2.7% for tirzepatide versus 5.6% for semaglutide. The combined effect on body weight exceeds what either pathway produces alone. SURMOUNT-1 data confirmed dose-dependent fat mass reduction, with approximately 75% of total weight loss coming from fat tissue and 25% from lean mass.
FDA-approved dual GIP/GLP-1 agonist with the strongest weight-loss efficacy of any approved drug class. SURMOUNT-1 demonstrated up to 22.5% mean body weight reduction at 15 mg over 72 weeks. SURMOUNT-5 proved superiority over semaglutide 2.4 mg (−20.2% vs −13.7%). SURPASS-CVOT showed non-inferiority (not superiority) to dulaglutide for major cardiovascular events. Additional FDA approvals: obstructive sleep apnea (Dec 2024). SUMMIT (HFpEF) and SYNERGY-NASH (MASH) trials positive.
SURMOUNT-1 (NEJM 2022, PMID 35658024): n=2,539 adults with obesity (no T2D), 72 weeks; −15.0% (5mg), −19.5% (10mg), −20.9% (12.5mg), −22.5% (15mg) mean body weight. SURMOUNT-5 (NEJM 2025, PMID 40353578): n=751, open-label head-to-head, −20.2% tirzepatide vs −13.7% semaglutide 2.4mg at 72 weeks; 19.7% of tirzepatide patients lost ≥30% body weight vs 6.9% semaglutide. GI discontinuation rate lower with tirzepatide (2.7% vs 5.6%).
Weight is largely regained after discontinuation: ~two-thirds within 12 months (SURMOUNT extension). Long-term human data beyond 72 weeks is limited outside of the 3-year T2D prevention endpoint. Black box warning for thyroid C-cell tumors remains: human relevance unknown. Approximately 25% of lost weight is lean mass without active resistance training. SURPASS-CVOT met non-inferiority vs dulaglutide but did not meet superiority on primary MACE endpoint (HR 0.88, p=0.09 for superiority). No head-to-head cardiovascular outcomes data vs semaglutide.
Strongest community enthusiasm of any GLP-1. r/Zepbound users consistently report superior appetite suppression and weight loss vs their prior semaglutide experience. Primary concerns: cost and insurance denials, GI side effects during escalation, muscle loss, and fear of lifelong dependency. Slow titration (6-8 weeks per step vs FDA's 4 weeks) is the dominant community protocol for GI tolerance.
Science and community fully agree on core findings: tirzepatide produces 20%+ weight loss at maximum tolerated doses, GI side effects are the limiting factor during titration, and weight returns when stopped. Community-evolved slow titration (6-8 week steps) is evidence-consistent and not in label. Community preference to stay at lowest effective dose (not always escalating to 15mg) aligns with clinical guidance that the right dose is the lowest achieving therapeutic goals.
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 2,500mcg | Weekly |
| Moderate | 5mg | Weekly |
| Aggressive | 10mg | Weekly |
Tirzepatide comes in pre-filled pens (brand Zepbound/Mounjaro) and compounded vials (very limited availability since March 2025). For compounded vials: Reconstitution math for a 10 mg vial with 2 mL bacteriostatic water gives you 5 mg/mL. A 2.5 mg dose is 0.5 mL (50 units on an insulin syringe). A 5 mg dose is 1.0 mL (100 units, a full syringe). For a 15 mg vial with 2 mL BAC water, concentration is 7.5 mg/mL. A 7.5 mg dose is 1.0 mL (100 units). A 10 mg dose runs about 1.33 mL, which exceeds a standard 1 mL syringe; either use a 3 mL syringe or reconstitute with 3 mL instead (giving 5 mg/mL, then 2.0 mL per 10 mg dose). The thing most beginners miss: 2.5 mg is not a therapeutic dose for weight loss. It's a tolerability test. Don't judge whether tirzepatide "works" until you've been at 5 mg for at least 4 weeks. Evening injections help most people sleep through the nausea window (4 to 8 hours post-dose).
Intended for long-term use. Weight regain expected upon discontinuation. Maintenance dosing may be lower than escalation dose.
Tirzepatide is an FDA-approved medication intended for continuous long-term use, not cycled like research peptides. Weight regain begins within weeks of discontinuation and most patients regain approximately two-thirds of lost weight within 12 months of stopping (SURMOUNT-1 extension data). The cyclingProtocol in peptides.ts (onWeeks: 52, offWeeks: 0) accurately reflects this: indefinite continuous use is standard practice. Any dose reductions should be gradual and medically supervised. The clinical question is not "when to cycle off" but "what is the lowest effective maintenance dose."
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Expected: SURMOUNT-1 at 72 weeks: −15.0% (5mg), −19.5% (10mg), −20.9% (12.5mg), −22.5% (15mg) mean body weight vs placebo. SURMOUNT-5: −20.2% at maximum tolerated dose vs −13.7% for semaglutide 2.4mg (72 weeks, open-label head-to-head).
Monitor: A1c and fasting glucose at baseline and 3-month intervals (T2D). Renal function if significant GI fluid losses. TSH if symptoms of thyroid disease. Serum lipase only if severe abdominal pain (not routine screen). Lipid panel and blood pressure at 6-month intervals. Weight and waist circumference monthly.
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Raised RHR +3bpm, lowered HRV -7pts, sleep quality -10%. Halted after 3 weeks.
Gather supplies: tirzepatide vial (or pre-filled pen), bacteriostatic water (if reconstituting a vial), alcohol swabs, insulin syringe (31-32 gauge, 4-6 mm needle for subcutaneous injection).
If using a compounded vial: add 2 mL bacteriostatic water slowly down the side of the vial. Swirl gently until dissolved. Never shake. For a 10 mg vial, final concentration is 5 mg/mL. For a 15 mg vial, concentration is 7.5 mg/mL.
At 5 mg/mL concentration: 50 units on the syringe equals 2.5 mg. 100 units equals 5 mg. At 7.5 mg/mL concentration: 100 units equals 7.5 mg. 67 units equals approximately 5 mg. Calculate your dose carefully for each vial concentration.
Choose abdomen (2 inches from the navel), thigh (front or outer), or upper arm. Rotate sites each week.
Pinch the skin gently and insert the needle at a 90-degree angle. Inject slowly and hold for 5 to 10 seconds before withdrawing.
Many users prefer evening injections to sleep through the 4 to 8 hour nausea window. Timing relative to meals isn't critical, but small, low-fat meals for 24 to 48 hours after injection improve tolerability.
Increase by 2.5 mg every 4 weeks (or 6 to 8 weeks per the community protocol if GI symptoms persist). Target your lowest effective dose; not everyone needs 15 mg.
Storage: refrigerate reconstituted vials at 2-8 degrees C (36-46 degrees F). Use within 4 weeks. Brand pens follow the same storage requirements. Pre-filled pens can be stored at room temperature (up to 30 degrees C / 86 degrees F) for up to 21 days per the Zepbound label.
Community-used adjunct for GI side effects of tirzepatide. BPC-157 supports gastric mucosal healing and may reduce nausea and GI inflammation during dose escalation. No clinical trial data exists for this combination.
BPC-157 250–500 mcg daily SC or oral (TB form) during dose escalation phases.
Anti-inflammatory tripeptide used by community members with co-occurring IBS or IBD and obesity. Hypothesized to complement gut health during GI-heavy tirzepatide side effect phases. No clinical data.
500 mcg oral daily, concurrent with tirzepatide use.
Community stack for energy support and mitochondrial function during caloric deficit and rapid weight loss. No known interaction with tirzepatide. No clinical data for this combination.
Both activate GLP-1 receptors: combining produces additive GLP-1 stimulation with dramatically increased nausea, vomiting, dehydration, and hypoglycemia risk. No additive benefit over tirzepatide monotherapy. When switching from semaglutide to tirzepatide, allow at least one half-life (~7 days) before starting tirzepatide to avoid overlap.
Do not combineGLP-1 receptor agonist: overlapping mechanism with tirzepatide's GLP-1 component. Combination increases GI side effects and hypoglycemia risk with no additive weight-loss benefit.
Do not combineTriple agonist (GIP/GLP-1/GCG) with fully overlapping GIP and GLP-1 receptor targets. Combining is mechanistically redundant and dramatically increases GI side effects and hypoglycemia risk.
Do not combineGH secretagogue that significantly stimulates appetite via the ghrelin pathway: directly antagonizes tirzepatide's primary appetite-suppression mechanism. Also promotes insulin resistance, opposing tirzepatide's glycemic benefits.
Do not combinePricing updated 2026-04-09
Tirzepatide carries a black box warning for thyroid C-cell tumors. In rodent studies, it caused dose-dependent increases in thyroid C-cell tumors, including medullary thyroid carcinoma (MTC). Whether this translates to humans is unknown, and no confirmed human cases have been attributed to tirzepatide. The drug is contraindicated in anyone with a personal or family history of MTC or Multiple Endocrine Neoplasia syndrome type 2 (MEN2). Gastrointestinal side effects are the most common reason people struggle with tirzepatide. In the SURMOUNT and SURPASS trials, nausea affected 17 to 25% of patients (dose-dependent, worst during dose escalation). Diarrhea occurred in 13 to 17%. Vomiting hit 8 to 10%. Constipation affected 7 to 11%. Most of these effects are mild-to-moderate and improve with slow dose titration; the community-preferred 6 to 8 week steps between dose increases reduce GI burden compared to the FDA label's 4-week minimum. Decreased appetite (9 to 11%) is technically a side effect, though most users consider it the primary benefit. Sulfur burps are a community-reported nuisance during escalation phases that clinical trials don't track well. Hair thinning (telogen effluvium) affects roughly 4 to 5% of users versus about 1% on placebo. This isn't a direct drug effect. Rapid weight loss and caloric restriction trigger a hair growth cycle shift that typically starts 2 to 3 months in and resolves on its own by month 9 to 12. Injection-site reactions occur in 4 to 7% of patients. Rotating injection sites between the abdomen, thigh, and upper arm helps. Let the vial reach room temperature for 15 to 20 minutes before injecting. Pancreatitis is rare but serious. Severe, persistent abdominal pain warrants immediate medical evaluation. Serum lipase testing should happen only when pancreatitis is clinically suspected; routine screening isn't indicated. Gallbladder disease and hypersensitivity reactions are uncommon but documented in clinical trials. Stop tirzepatide and seek medical care if you develop signs of anaphylaxis, severe abdominal pain, or jaundice. Muscle loss is a legitimate concern. Approximately 25% of weight lost on tirzepatide is lean mass (SURMOUNT-1 body composition data). Resistance training 3 to 4 times per week and protein intake of at least 1.2 g/kg body weight per day are the primary countermeasures. Pregnancy and breastfeeding: tirzepatide is contraindicated. Stop treatment at least 2 months before planned conception due to the 5-day half-life and limited reproductive safety data.
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Brand-name Zepbound and Mounjaro are FDA-regulated Eli Lilly products manufactured to GMP standards with consistent potency and sterility. Compounded tirzepatide is largely unavailable: FDA ended enforcement discretion for 503A pharmacies Feb 18, 2025 and 503B outsourcing facilities March 19, 2025. A federal court upheld the FDA's decision in May 2025. As of April 2026, tirzepatide remains on the FDA shortage list, allowing limited 503A compounding only for individual patients with documented medical necessity (specific dose requirements or allergies to inactive ingredients). The LillyDirect self-pay vial program offers brand Zepbound (not compounded) at reduced cost.
| Test | When | Target |
|---|---|---|
| HbA1c and fasting plasma glucose | Baseline, then every 3 months (T2D) or every 6 months (obesity without diabetes) | HbA1c <7.0% (T2D); fasting glucose 70-100 mg/dL |
| Body weight and waist circumference | Monthly minimum; at every clinical encounter | — |
| Lipid panel (LDL-C, HDL-C, triglycerides, non-HDL-C) | Baseline, 3-6 months, then annually | — |
| Serum creatinine / eGFR | Baseline, then at 3-6 months: especially if significant GI fluid losses during escalation | — |
| TSH (thyroid stimulating hormone) | Baseline; repeat if symptoms of thyroid disease develop (neck mass, hoarseness, dysphagia) | — |
| Serum lipase | Only if severe persistent abdominal pain occurs: NOT a routine screening test | — |
| Resting heart rate | At each clinical encounter or via home monitoring | Increase <20 bpm above personal baseline; refer for cardiology review if exceeding this |
| Body composition (DEXA or InBody) | Optional: baseline and every 6-12 months for users prioritizing lean mass preservation | — |
Primary efficacy endpoint for T2D. Monitor for hypoglycemia if on concurrent insulin or sulfonylureas. Target A1c <7.0% for T2D patients per ADA guidelines.
Primary efficacy marker for obesity indication. Less than 5% weight loss at 16 weeks on highest tolerated dose is a signal to reassess treatment.
Tirzepatide significantly improves lipid profile alongside weight loss. Baseline establishes comparison point.
GI side effects (vomiting, diarrhea) can cause dehydration and AKI. Monitor renal function during dose escalation phases.
Black box warning for thyroid C-cell tumors (rodent data; human relevance unknown). Contraindicated in personal/family history of MTC or MEN2. Baseline TSH provides clinical reference point.
To rule out acute pancreatitis, which is rare but serious. GI side effects of tirzepatide can mimic pancreatitis symptomatically.
GLP-1 agonists increase resting heart rate (mean +1-2 bpm with tirzepatide, less than semaglutide per SURMOUNT-5). Clinically relevant for patients with arrhythmia history.
SURMOUNT-1 data: ~25% of weight loss is lean mass. Provides objective data on resistance training protocol efficacy. Not required per FDA label but recommended by obesity medicine specialists.
Starting dose 2.5mg weekly. Appetite suppression begins within days. Nausea is most common but usually mild. Minimal weight loss expected: this is a tolerability phase.
Dose escalated to 5mg. Noticeable hunger reduction. Early weight loss of 2-4% body weight. GI side effects typically improving.
Dose escalated to 7.5mg. Steady weight loss continues. Blood sugar improvements measurable on labs.
Dose escalated to 10mg. Significant appetite changes. Cumulative weight loss approaching 8-10%.
Dose escalated to 12.5mg, then 15mg if tolerated. Maximum efficacy phase begins. SURMOUNT-1 showed 22.5% weight loss at 72 weeks on 15mg.
Maintenance at maximum tolerated dose (5-15mg). Weight loss continues to plateau around 20-25%. Cardiovascular and metabolic markers significantly improved.
Weeks 1 to 4, Tolerability Phase (2.5 mg): Clinical trials showed negligible weight change at 2.5 mg because this dose exists purely for GI tolerance. Community experience tells a different story on appetite, though. Most users on r/Zepbound report food noise diminishing within days of their first injection. Some drop 2 to 5 lbs in the first week, mainly water weight and reduced GI volume. Side effects at this dose are mild for most: light nausea, fatigue, decreased appetite. Don't evaluate whether tirzepatide works based on this phase. Weeks 5 to 12, Dose Escalation (5 to 7.5 mg): Each 2.5 mg step-up triggers a GI flare that typically lasts 1 to 2 weeks before the body adapts. The community calls 5 mg "the wall" because nausea peaks here for many users. Cumulative weight loss of 3 to 6% is expected by week 12. Constipation becomes a persistent companion; daily fiber and adequate water are non-negotiable. Sulfur burps and fatigue during the first week at each new dose are commonly reported. Visible weight loss starts validating the discomfort. Weeks 13 to 20, Reaching Maintenance Dose (7.5 to 12.5 mg): Most users find their sweet spot somewhere in this range. Food noise goes largely silent. Energy improves. Community posts shift from asking "does this work?" to discussing muscle preservation, clothing sizes, and whether to keep escalating. Cumulative weight loss sits at 8 to 14% depending on dose. Lab markers (A1c, blood pressure, triglycerides) show measurable improvement. GI side effects decrease substantially at a stable dose, but constipation sticks around. Hair thinning may start for some. Weeks 21 to 52, Maximum Efficacy Phase: Weight loss continues accumulating toward the 20 to 22% range at maximum tolerated dose. SURMOUNT-1 data showed roughly 20 to 22% reduction by week 52 at 15 mg. Side effects are minimal once you've been at a stable dose for several weeks. Sleep apnea resolution is commonly reported. Reduced alcohol cravings show up frequently in community posts. Telogen effluvium starts resolving. Some people report cold intolerance as they lose significant weight. Week 72 and beyond, Long-term Maintenance: Weight loss plateaus around 20 to 22.5% at maximum dose. The SURMOUNT-1 three-year follow-up [6] showed 94% type 2 diabetes prevention in the prediabetes group versus 40% with lifestyle changes. Community discussion centers on one question: "can I ever stop?" Consensus points to indefinite treatment for most, similar to blood pressure or cholesterol medications. Some experiment with gradual dose reductions. Cost and insurance remain the dominant long-term concerns. Weight regain within weeks of stopping or reducing dose is the consistent theme across both trial data and community reports.
Minimal weight loss. Purpose is GI tolerance establishment. Mean weight change at 4 weeks is negligible in clinical trials.
Most users notice appetite suppression within days of first injection even at 2.5 mg. Some lose 2-5 lbs in week 1, often water weight and reduced GI volume. Community excitement is high; many are surprised how quickly food noise diminishes.
Each 2.5 mg step-up produces a transient GI side effect flare for 1-2 weeks before adaptation. Cumulative weight loss 3-6% by week 12 expected.
GI side effects peak at the 5 mg step for many users. Community calls this "the 5 mg wall." Most push through with slow titration. Visible weight loss validating the side effects. Body composition changes begin.
Cumulative weight loss 8-14% by week 20 depending on dose. A1c, blood pressure, and triglycerides show significant improvement.
Many users find their "sweet spot" dose (often 7.5-12.5 mg). Food noise largely silent. Energy improving. Posts shift from "does it work?" to muscle preservation, clothing sizes, and dose decisions. SURMOUNT-5 results widely discussed: community validates head-to-head superiority over semaglutide.
Weight loss continues to accumulate and plateau. SURMOUNT-1: ~20-22% loss by week 52 at 15mg. HbA1c, blood pressure, and lipids substantially improved. Cardiovascular risk factors declining.
Sustained weight loss. Community focus shifts to maintenance, muscle preservation, and long-term planning. Sleep apnea resolution commonly reported. Alcohol cravings reduced. "I forgot what hunger feels like" is a common theme.
Weight loss plateaus around 20-22.5% at maximum dose. SURMOUNT-1 3-year follow-up: 94% T2D prevention in prediabetes group (vs 40% lifestyle alone). Weight regain of ~two-thirds within 12 months of discontinuation.
Weight loss has stabilized. Many debating "Can I ever come off?" Community consensus: likely a lifelong treatment for most, similar to antihypertensives or statins. Some experiment with dose reductions. Cost and insurance are dominant long-term concerns.
Source: Mounjaro FDA Label, Section 12.3; confirmed by PopPK analysis (t½ ~117h)
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Tirzepatide is FDA-approved under two brand names: Mounjaro (type 2 diabetes, approved May 2022) and Zepbound (chronic weight management, approved November 2023). A third indication for moderate-to-severe obstructive sleep apnea with obesity was approved in December 2024. Tirzepatide requires a prescription in the United States and most countries. Compounded tirzepatide availability changed significantly in 2025. The FDA ended enforcement discretion for 503B outsourcing facilities on March 19, 2025, and for 503A pharmacies on February 18, 2025. A federal court upheld this decision in May 2025. As of April 2026, tirzepatide remains on the FDA shortage list, allowing very limited 503A compounding only for patients with documented medical necessity (specific dose requirements or allergies to inactive ingredients). LillyDirect offers brand Zepbound vials (not compounded) on a self-pay basis ranging from $299 to $499 per month. Tirzepatide is on the WADA Prohibited List under S2 (Peptide Hormones, Growth Factors, Related Substances, and Mimetics) for competitive athletes. This content is for informational purposes only and does not constitute medical advice. Consult a licensed healthcare provider before starting any medication.
Peptide Schedule Research TeamReviewed Apr 202613 Citations
