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FDA-approved drug

Tirzepatide, measured: what the trials actually showed

One molecule, two hormone receptors, and an unusually deep trial record. In the first head-to-head trial against semaglutide in obesity, tirzepatide reduced body weight by 20.2% versus 13.7% over 72 weeks. Every number on this site traces to the FDA label or the trial that produced it.

View tirzepatide plansBrowse the guides
  • 27cited sources
  • 25,523trial participants in our evidence table
  • 68in-depth guides

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Prescription treatment requires an online medical evaluation. A provider will determine whether treatment is medically appropriate; approval is not guaranteed.

Key facts

  • StatusFDA-approved drug
  • RouteSubcutaneous injection, once weekly (abdomen, thigh, or back of upper arm)
  • TmaxMedian 24 hours (range 8 to 72 hours)
  • Volume of distributionApproximately 10.3 L (type 2 diabetes population); 99% bound to plasma albumin
  • ClearanceApproximately 0.061 L/h
  • Drug classDual GIP and GLP-1 receptor agonistFDA labelsource
  • Half-lifeAbout 5 daysFDA labelsource
  • Dosing frequencyOnce weekly subcutaneous injectionFDA labelsource
  • Dose range2.5 to 15 mg once weeklyFDA labelsource
  • Time to peak level24 hours (range 8 to 72)FDA labelsource
  • Steady stateAbout 4 weeks of weekly dosingFDA labelsource
  • Bioavailability80% subcutaneousFDA labelsource

Read the full Tirzepatide monograph

Browse by topic

Everything on tirzepatide, organized the way you research it.

Safety19 articlesEvidence17 articlesSourcing14 articlesDosing12 articlesComparisons6 articles

Free Tirzepatide tools

Practical calculators and references, each scoped and sourced.

T-01Titration plannerA dated week-by-week view of the label's dose-escalation ladder from the start date you choose.T-02Dose unit converterTwo-way conversion between mg, mcg, mL, and U-100 syringe units at the concentration you state.T-03Study dose explorerEvery dose reported in the published literature for this compound, filterable by species and route, each row sourced.
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All guides

68 in-depth, individually cited guides.

Safety 19 guides

Tirzepatide and alcohol: what actually happens if you mix themTirzepatide doesn't block alcohol's effects, but it can intensify nausea, low blood sugar risk, and dehydration. Here's the trial data and what to actually do.Updated 2026-07-30Read guide →
Tirzepatide and antidepressants: safety and interactionsNo major drug interaction exists between tirzepatide and antidepressants, but slower gut emptying can change how oral pills absorb. Here's what trials and the FDA label say.Updated 2026-07-30Read guide →
Tirzepatide and birth control: what the evidence saysOral birth control may work less well on tirzepatide, mainly at dose increases. Zepbound's label recommends backup or switching methods for 4 weeks.Updated 2026-07-30Read guide →
Tirzepatide and caffeine: what actually happens when you mix themNo trial data show a direct tirzepatide-caffeine interaction, but slower gastric emptying and dehydration risk change how caffeine hits you. Here's the real picture.Updated 2026-07-30Read guide →
Tirzepatide and pregnancy: what the evidence actually saysZepbound and Mounjaro labels say stop tirzepatide at least 1 month before trying to conceive. Here's the animal data, contraception rules, and what to do if you conceive on it.Updated 2026-07-30Read guide →
Tirzepatide common mistakes: 12 errors that stall resultsWrong injection sites, skipped titration, no protein, alcohol on top of nausea: here are the tirzepatide mistakes that cause most side effects and stalled weight loss.Updated 2026-07-30Read guide →
Tirzepatide not working? 12 real reasons and fixesTirzepatide non-response has real causes: dose too low, wrong titration, diet gaps, or genuine plateau. Trial data on responder rates and what to do next.Updated 2026-07-30Read guide →
Tirzepatide overdose and toxicity: signs, risks, and what to doTirzepatide overdose is rare but real. Learn the symptoms, why compounding errors raise the risk, and the FDA/poison control steps to take right now.Updated 2026-07-30Read guide →
Tirzepatide rebound effect: what happens after you stopTrial data show most regained weight comes back within a year of stopping tirzepatide. Here's what SURMOUNT-4 found and how to plan around it.Updated 2026-07-30Read guide →
Tirzepatide withdrawal and stopping: what happens off the drugStopping tirzepatide isn't like opioid or alcohol withdrawal. Here's what SURMOUNT trial data shows about weight regain, GI symptoms, and how to taper safely.Updated 2026-07-30Read guide →
Is Tirzepatide FDA approved? what that question actually meansTirzepatide is an information platform, not a drug. Only tirzepatide itself (Mounjaro, Zepbound) is FDA approved. Here's how to check what you're getting.Updated 2026-07-27Read guide →
Is tirzepatide safe? what the trial data actually showsTirzepatide safety by the numbers: GI side effects in 70%+ of trial patients, a boxed MTC warning, and what SURMOUNT and SURPASS actually found.Updated 2026-07-27Read guide →
Tirzepatide and athletes: drug testing rules explainedIs tirzepatide banned in sport? WADA doesn't list GLP-1/GIP drugs on the 2025 Prohibited List, but athletes should still know the gray areas. Here's the evidence.Updated 2026-07-27Read guide →
Tirzepatide and blood work: what to test and whenWhich labs matter before and during tirzepatide treatment, how often to recheck them, and what SURPASS and SURMOUNT trial data show about changes over time.Updated 2026-07-27Read guide →
Tirzepatide contraindications: who should not use itA personal or family history of MTC or MEN2 is an absolute contraindication. Full breakdown of who should avoid tirzepatide, per FDA labeling and SURMOUNT/SURPASS data.Updated 2026-07-27Read guide →
Tirzepatide drug interactions: what actually conflictsFull breakdown of tirzepatide drug interactions: oral meds slowed by delayed gastric emptying, insulin/sulfonylureas, warfarin, birth control pills, and more.Updated 2026-07-27Read guide →
Tirzepatide in women: weight loss, PCOS, and safety dataWomen lost 15-21% of body weight on tirzepatide in SURMOUNT trials. Here's what the data says on PCOS, fertility, menstrual cycles, pregnancy risk, and dosing.Updated 2026-07-27Read guide →
Tirzepatide long term side effects: what the trials show5-year SURMOUNT data on tirzepatide's long term side effects: GI symptoms, gallbladder risk, pancreatitis signal, and the MTC boxed warning explained.Updated 2026-07-27Read guide →
Tirzepatide side effects: the real risk profile, by trial dataNausea hits 12-24% of tirzepatide users across dose levels; gallbladder disease and a rodent thyroid tumor warning are the bigger long-term concerns. Full breakdown.Updated 2026-07-27Read guide →

Evidence 17 guides

How long until tirzepatide works: a week-by-week timelineMost people notice appetite changes in 1-2 weeks, real weight loss by week 4-8, and full effect around month 9-11. Here's the trial data behind that timeline.Updated 2026-07-30Read guide →
Is tirzepatide worth it? A real-numbers reality checkZepbound users lost 20.9% of body weight at 72 weeks in SURMOUNT-1. Here's what tirzepatide actually costs, does, and risks before you decide.Updated 2026-07-30Read guide →
Natural alternatives to tirzepatide: what actually worksBerberine, fiber, GLP-1 foods and lifestyle changes vs tirzepatide's 15-21% weight loss in trials. What the evidence really supports, and what doesn't.Updated 2026-07-30Read guide →
Tirzepatide before and after: what the trials actually showWhat weight and A1C changes look like on tirzepatide, backed by SURMOUNT and SURPASS trial data, real timelines, and honest limits of before/after photos.Updated 2026-07-30Read guide →
Tirzepatide first month: what to expect week by weekIn month one, most people start at 2.5 mg, lose 2-4% of body weight, and deal with mild GI side effects. Here's what the SURMOUNT trials actually show.Updated 2026-07-30Read guide →
Tirzepatide FAQ: dosing, side effects, cost, and resultsAnswers to the most-asked tirzepatide questions: dosing, weight loss %, side effects, cost, Mounjaro vs Zepbound, and compounded vs brand, with trial data.Updated 2026-07-30Read guide →
Tirzepatide in older adults: what the trial data showsSURPASS and SURMOUNT data on tirzepatide in adults over 65: efficacy, GI side effects, muscle loss risk, and dosing cautions explained with trial numbers.Updated 2026-07-30Read guide →
Tirzepatide myths vs facts: what the trials actually showTirzepatide claims checked against SURMOUNT and SURPASS data: real weight loss numbers, side effect rates, and what's still unproven.Updated 2026-07-30Read guide →
Tirzepatide pros and cons: what the trial data really showsTirzepatide cut A1C by up to 2.58% and body weight by up to 22.5% in trials, but GI side effects and a thyroid cancer warning are real. Full breakdown.Updated 2026-07-30Read guide →
Tirzepatide reviews: what the trials and users actually reportReal tirzepatide reviews backed by trial data: 15-20% weight loss in SURMOUNT, common side effects, who it doesn't work for, and what long-term users say.Updated 2026-07-30Read guide →
Tirzepatide success rate: what the trials actually showUp to 91% of Zepbound users lost 5%+ weight in SURMOUNT-1, and average loss hit 20.9% at 72 weeks. Here's the real data by dose and use case.Updated 2026-07-30Read guide →
Tirzepatide: animal studies vs human trial evidenceRodent thyroid tumors vs SURPASS and SURMOUNT human data: what tirzepatide's animal studies actually showed, and why the FDA still approved it.Updated 2026-07-27Read guide →
Tirzepatide before and after claims: what the trials actually showBefore and after photos aren't data. Here's what SURMOUNT and SURPASS actually recorded on tirzepatide weight loss and A1C over 36 to 72 weeks.Updated 2026-07-27Read guide →
Tirzepatide clinical trials: what SURMOUNT and SURPASS showSURMOUNT-1 showed up to 22.5% weight loss at 72 weeks; SURPASS trials cut A1C by up to 2.4 points. Here's what the tirzepatide trial data actually says.Updated 2026-07-27Read guide →
Tirzepatide human studies: what the trials actually showSURPASS and SURMOUNT enrolled over 15,000 people. Here's what the tirzepatide human studies found on weight loss, A1c, and side effects, trial by trial.Updated 2026-07-27Read guide →
Tirzepatide mechanism of action: how the drug actually worksTirzepatide activates GLP-1 and GIP receptors together. Here's the receptor biology, trial data (SURMOUNT, SURPASS), and what it means for side effects and dosing.Updated 2026-07-27Read guide →
Tirzepatide results: what the trial evidence showsSURMOUNT and SURPASS trial data on tirzepatide: up to 22.5% weight loss and A1C drops of 2.1 points. See the real numbers, timelines, and risks.Updated 2026-07-27Read guide →

Sourcing 14 guides

Tirzepatide compounded vs brand name: the real differencesZepbound and Mounjaro are FDA-approved; compounded tirzepatide is not. Here's what that actually means for safety, cost, dosing, and legal access in 2026.Updated 2026-07-30Read guide →
Tirzepatide cost per month: what it actually runs in 2026Zepbound and Mounjaro list price is $1,086.37/month without insurance. Here's what people actually pay after insurance, savings cards, and compounding.Updated 2026-07-30Read guide →
Tirzepatide online prescription requirements, explainedLegit online tirzepatide requires a licensed prescriber, real med history review, and a valid prescription. Here's what's required, what's a red flag, and what it costs.Updated 2026-07-30Read guide →
Tirzepatide price without insurance: real 2025 numbersZepbound list price is $1,059.87/month, Mounjaro $1,069.03. Compounded versions run $150-500/month. Here's what actually determines your cost.Updated 2026-07-30Read guide →
Tirzepatide telehealth options: what actually gets you the drugTelehealth can prescribe branded Zepbound or Mounjaro, or refer you to a compounding pharmacy. Here's what's legal, what it costs, and what to check first.Updated 2026-07-30Read guide →
Where to buy tirzepatide legally: a buyer's reality checkLegal routes: Zepbound/Mounjaro via licensed pharmacy with prescription, or compounded from a 503A/503B pharmacy. Here's what's real, what's risky, and what's fake.Updated 2026-07-30Read guide →
How to verify tirzepatide quality before you inject itA practical checklist for verifying tirzepatide quality: COA review, USP <797> facts, FDA shortage status, and questions every compounding pharmacy should answer.Updated 2026-07-27Read guide →
Tirzepatide certificate of analysis explainedWhat a tirzepatide COA should show, what third-party testing costs, and how to spot a fake report before you trust a vial.Updated 2026-07-27Read guide →
Compounding pharmacy vs research supplier for tirzepatideCompounding pharmacies require a prescription and licensed oversight; research suppliers sell unregulated peptides with no chain of custody. Here's the real difference.Updated 2026-07-27Read guide →
Tirzepatide cost and pricing: what it really costs in 2025Zepbound list price is $1,059.87/month. Insurance, savings cards, and compounded routes change that math a lot. Here's the real breakdown.Updated 2026-07-27Read guide →
Tirzepatide legal status: what's actually FDA-approvedZepbound and Mounjaro are FDA-approved; compounded tirzepatide is legal in narrower cases. Here's the real regulatory picture, sourced from FDA and NCT trial data.Updated 2026-07-27Read guide →
Tirzepatide prescription requirements: what you actually needTirzepatide requires a prescription by federal law (FDCA Section 503). Here's what a legit prescriber checks, what disqualifies you, and how telehealth actually works.Updated 2026-07-27Read guide →
Tirzepatide purity and testing: what buyers should verifyFDA-approved tirzepatide has 99%+ purity by USP standard. Compounded versions vary. Here's what testing actually proves and how to check before you buy.Updated 2026-07-27Read guide →
What does Tirzepatide actually do, exactly?Updated 2026-07-27Read guide →

Dosing 12 guides

Tirzepatide for beginners: the complete starter guideNew to tirzepatide? Learn how it works, the 2.5-15mg dosing ladder, real trial results (up to 20.9% weight loss), side effects, and what to expect week by week.Updated 2026-07-30Read guide →
Does tirzepatide need to be refrigerated?Unopened tirzepatide needs a fridge (36-46°F). Once in use, most pens/vials tolerate room temp for 21-30 days. Here's the FDA-sourced breakdown by product.Updated 2026-07-27Read guide →
How long does tirzepatide take to work?Tirzepatide can curb appetite within days, but real weight loss and A1C drops build over 4 to 9 months. Here's the week-by-week timeline from trial data.Updated 2026-07-27Read guide →
How to reconstitute tirzepatide: a step-by-step protocolHow to reconstitute compounded tirzepatide correctly: BAC water ratios, mixing technique, storage times, and the mistakes that ruin a vial. Step-by-step guide.Updated 2026-07-27Read guide →
Tirzepatide cycle length: how long should a course run?There's no fixed tirzepatide cycle. SURMOUNT trials ran 36-72 weeks continuously. Here's what the data says about duration, titration, and stopping.Updated 2026-07-27Read guide →
Tirzepatide dosage: the full titration schedule explainedTirzepatide starts at 2.5mg weekly and titrates to a 15mg max. Here's the full FDA schedule from SURMOUNT and SURPASS, with real numbers on timing and side effects.Updated 2026-07-27Read guide →
Tirzepatide dosage calculator: how the math actually worksA tirzepatide dosage calculator only converts mg to mL and units. See the real FDA titration schedule (2.5mg to 15mg) and how to check any calculator's math.Updated 2026-07-27Read guide →
Tirzepatide half life: how long it stays in your systemTirzepatide's half life is about 5 days, per FDA labeling. See what that means for dosing intervals, missed doses, washout time, and drug clearance.Updated 2026-07-27Read guide →
How to inject tirzepatide: a step-by-step protocolTirzepatide is injected subcutaneously once weekly. Here's the full injection protocol: needle size, sites, angle, rotation, and what the SURMOUNT trials actually used.Updated 2026-07-27Read guide →
Tirzepatide injection sites: where and how to injectAbdomen, thigh, or upper arm: the FDA label allows all three. Here's the injection site rotation schedule that actually cuts down on skin reactions.Updated 2026-07-27Read guide →
Tirzepatide storage and shelf life: the real rulesUnopened tirzepatide stays cold (2-8°C) until the expiration date; in-use pens last 21-31 days at room temp. Here's what the labels actually say.Updated 2026-07-27Read guide →
Tirzepatide timeline: what to expect week by weekWhat happens on tirzepatide from week 1 to month 18, based on SURMOUNT and SURPASS trial data. Dosing, side effects, and weight loss by timepoint.Updated 2026-07-27Read guide →

Comparisons 6 guides

Tirzepatide alternatives: how the real options compareSemaglutide, retatrutide, orforglipron, and lifestyle programs, compared against tirzepatide's SURMOUNT and SURPASS data on weight loss and side effects.Updated 2026-07-30Read guide →
Tirzepatide vs Mounjaro vs Zepbound: what actually differsMounjaro and Zepbound are the same FDA drug, tirzepatide, at different doses for different labels. Here's the real trial data, cost, and how compounded fits in.Updated 2026-07-27Read guide →
Tirzepatide vs Ozempic: comparing tirzepatide and semaglutideTirzepatide vs semaglutide (Ozempic): SURPASS/SURMOUNT vs STEP trial data, weight loss %, dosing, side effects, and cost compared head-to-head.Updated 2026-07-27Read guide →
Tirzepatide vs retatrutide: how the two GLP-1 drugs compareTirzepatide has FDA approval and phase 3 data showing up to 20.9% weight loss. Retatrutide is still in trials, with phase 2 results near 24%. Full comparison.Updated 2026-07-27Read guide →
Tirzepatide vs semaglutide: what the trial data showsHead-to-head trial data: tirzepatide averaged 15-21% weight loss vs semaglutide's 15%. Compare SURMOUNT, STEP, dosing, side effects, and cost.Updated 2026-07-27Read guide →
Tirzepatide vs Wegovy: how tirzepatide stacks upWegovy averaged 15.2% weight loss at 68 weeks; tirzepatide hit 20.9% at 72 weeks (SURMOUNT-1). Full head-to-head on dosing, cost, and side effects.Updated 2026-07-27Read guide →
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