GIP
An incretin pathway involved in insulin release and nutrient handling.
Retatrutide.
Retatrutide activates GIP, GLP-1 and glucagon receptors. Researchers study body-weight, glucose and liver-fat outcomes; community discussions focus on appetite control, gradual dose changes and the lowest amount that feels effective while allowing adequate eating.
Research focus: Body weight, appetite and metabolic outcomes.
Choose a compound to open its research, documentation and calculator.
QUICK REFERENCE
Checked October 15, 2026The essentials.
- FDA statusFDA status and scope
No FDA-approved drug product for this catalog material. Compounding eligibility and approval are separate questions.
Official source ↗ - Not FDA approved
- Half-lifeHalf-life: source and route
Investigational study preparation; plasma decline is not the duration of every biological effect.
Half-life describes concentration falling by half. It does not set a dosing interval, a storage period or a drug-test detection window.
Kinetics source ↗ - About 6 daysHuman · phase 1b study
- Diluent / formulationDiluent and formulation
PeptIQ lists bacteriostatic water for repeated-vial workflows. That preference is not a compatibility study for a particular formulation; the actual product or pharmacy instructions determine the liquid.
Bacteriostatic water contains a preservative; plain sterile water does not. Preservative presence does not by itself establish compatibility or a mixed medicine’s usable period.
Preparation source ↗ - BAC water · community-reportedCommunity reference
What the documentation tells us.
Evidence context
Retatrutide remains investigational and is not FDA approved. Trial findings do not establish an approved prescribing schedule or verify a separately supplied vial.
Check that a source concerns the same molecule, formulation, route and population. A study of cells, animals or a different product cannot confirm the contents of a vial.
Published trials, sponsor results and separately attributed community accounts.
One peptide, three receptor targets.
In plain English: retatrutide is designed to engage several of the body’s metabolic message systems with one molecule. An agonist is a substance that activates a receptor.
GLP-1
A pathway involved in glucose-dependent insulin release and appetite regulation.
Glucagon
A metabolic pathway being investigated for its contribution to energy expenditure. Early supporting experiments included mice.
The discovery work measured activity at all three receptors. Animal mechanisms do not establish the size of each receptor’s contribution in humans. Read the original discovery paper ↗
Published receptor assays · Coskun et al., 2022
What “receptor balance” measures.
Retatrutide’s activity differs across its three targets in laboratory assays. EC50 is the concentration producing half the maximum response in that assay; a lower value indicates greater potency, rather than a receptor that moves faster.
| Receptor | EC50 (nM) | Relative potency* |
|---|---|---|
| GIPR | 0.0643 | 8.9× native GIP |
| GLP-1R | 0.775 | 0.4× native GLP-1 |
| GCGR | 5.79 | 0.3× native glucagon |
*Compared with each receptor’s corresponding native peptide in the same study. These assay concentrations are different from an administered dose in mg.
Original receptor study ↗Community interpretation
Why the community discusses 4 mg.
About community receptor interpretations
The linked discussions are self-reports, not verified independent-doctor research. A receptor assay can suggest a pharmacological hypothesis, but it does not measure receptor contributions at a particular human dose.
The lower glucagon-receptor potency in these assays helps explain the idea that a higher exposure could change the balance of effects. Some community commenters describe 4 mg as a milestone. The discovery study found activity at all three receptors; it did not identify a universal 4 mg “switch-on” point in people.
Read the community discussion ↗Other names you may encounter: LY3437943.
Learn to read a study →Community schedules and research routes.
Dosage & schedule options.
Reading these schedules
Each entry keeps one schedule’s amount, frequency and cycle together. Community references, individual reports, clinical trials and prescription products describe different kinds of use. A missing duration or break stays marked as not reported.
Amounts describe mass in mg or mcg. Syringe units describe volume and depend on concentration. A cycle break is different from days off within a week.
Choose an option to explore its amounts, timing and cycle.
Reported protocolWeekly injections · phase 3 study
- Dose
- 2 mg initially; assigned targets 4, 9 or 12 mg
- How often
- Once weekly
- Route
- Subcutaneous
- Duration
- 80-week trial; 4-week escalation stages
- Break after cycle
- No scheduled cycle break in this trial
| When | Amount & frequency |
|---|---|
| Weeks 1–4 | 2 mg once weekly |
| Weeks 5–8 | 4 mg once weekly; 4 mg arm stays here |
| Weeks 9–12 | 6 mg once weekly for higher-target arms |
| Weeks 13–16 | 9 mg once weekly; 9 mg arm stays here |
| Week 17 onward | 12 mg once weekly in the 12 mg arm |
Individual community reportGradual weekly increases · reported use
- Dose
- 1 mg → 2 mg → 3 mg per weekly injection
- How often
- Once weekly
- Route
- Injected; injection type not reported
- Duration
- 4 weeks each at 1 mg, 2 mg and 3 mg (12 weeks reported)
- Break after cycle
- Not reported
An individual account with four weeks at each amount. It does not establish an automatic monthly increase for everyone.
Individual community reportLower starting amount · reported use
- Dose
- 0.5 mg weekly initially; later 2 mg weekly
- How often
- Weekly
- Route
- Injected; injection type not reported
- Duration
- 4 weeks at 0.5 mg; later 5 weeks at 2 mg reported
- Break after cycle
- Not reported
Intermediate escalation amounts were not reported, so this entry does not supply a complete ramp.
Individual community reportTwo-milligram stages · reported use
- Dose
- 2 → 4 → 6 mg per weekly injection
- How often
- Weekly
- Route
- Injected; injection type not reported
- Duration
- Four-week stages in the reported account
- Break after cycle
- Not reported
| When | Amount & frequency |
|---|---|
| First 4 weeks | 2 mg once weekly |
| Next 4 weeks | 4 mg once weekly |
| Later stage | 6 mg once weekly |
Community research & perspectives.
About community labels
Community identifies source origin. It does not certify independent funding, medical credentials or the strength of a claim. Source types distinguish published reports, professional explanations and public discussions.
Explore reports, explanations and discussions from medical practices, researchers, suppliers and community members. The badges identify the source’s origin and evidence type.
How to read these source labels →CommunityVendor explainer
Trial data and community starting charts
PeptIQ: evidence & source context
Not original clinical research or a representative survey. Its timing, preparation and switching suggestions are not validated by the cited trial.
Source relationship: Promotes its tracking app and includes telehealth referral disclosures.
The current article distinguishes trial schedules from community starting charts and explains concentration arithmetic. Individual forum schedules appear separately in our guide.
Commercial app explainer · trial and community context
CommunityCommunity discussion
UBT251 and Retatrutide: a community comparison
UBT251 and Retatrutide: a community comparison: evidence & source context
A forum explainer is not a head-to-head trial or an independently measured UBT251 receptor-potency table. Cross-trial outcomes cannot prove superiority, and an unreported adverse-event signal is not evidence of absence.
Source relationship: The post recommends a named supplier and describes a product without an available lot-specific certificate at the time of writing. Any financial relationship is unverified. Inclusion is not a supplier or product endorsement.
The post compares triple-receptor targets, trial headlines and a proposed difference in glucagon weighting. Its receptor-balance and tolerability interpretations are discussed alongside primary sources in our UBT251 research article.
Community interpretation · includes supplier promotion · clinical credentials unverified
CommunityCommunity discussion
Lower starts, gradual changes and differing tolerability
Lower starts, gradual changes and differing tolerability: evidence & source context
These are unverified personal accounts, not a clinician consensus or validated protocol. They do not establish that most users stay at 2–4 mg, or that hunger suppression alone determines effectiveness or safety.
Source relationship: Pseudonymous public discussion. Clinical credentials, product identity, funding and commercial relationships are not independently verified.
Some replies describe 1–2 mg starts, holding amounts for several weeks and seeking a lower effective amount. One reports four-week periods at 1, 2 and 3 mg; others report nausea at 1 mg, lower starts, or different schedules.
Self-reports · selected examples · no representative dose distribution
Reconstitution, storage and devices.
Product-specific handling
A peptide name and vial mass cannot determine a compatible diluent, powder displacement, storage temperature or discard date. Follow the exact product’s instructions and your pharmacist’s directions.
The injection guide concerns clinician-prescribed subcutaneous medicines; it does not establish that a research-labeled material can be injected.
Start with the formulation: dry powder, prepared solution, pen, tablet and topical product can have different instructions.
Storage: before and after opening.
Research-vial reference
Community-reported ranges- Dry powder · reported shelf life
- 12–24 months
- After mixing · reported window
- 21–30 days
- Refrigeration · reported range
- 2–8°C · 36–46°F
- Freezer
- Dry powder only in the reference
- Room temperature · reported limit
- Under 24 hours
- Handling note
- Keep the lot label, mixing date and documented discard date together.
Habits & tracking that help.
General health habits and consistent observations help you assess changes. They are not evidence that a peptide’s effects will be amplified.
Include movement and strength work
Choose activity that fits your health and ability. Aerobic movement and muscle-strengthening work are part of general adult activity guidance.
CDC · adult activity ↗Keep a consistent sleep routine
Use a regular sleep/wake schedule and note changes in sleep quality alongside symptoms or training.
CDC · sleep habits ↗What to record: Track food intake, appetite, activity and tolerability together. Appetite control should still leave room for adequate meals; review persistent eating difficulties with the treating clinician.
Documentation behind Retatrutide.
About source checks
Check dates are editorial references, not a medical review certificate. Labels and evidence can change; consult the linked current document.
StudyDiscovery: triple-receptor activity and early clinical researchStudyPhase 1b: pharmacokinetics and once-weekly study dosingStudyPhase 2: obesity trialStudyPhase 2: type 2 diabetes trialStudyPhase 2a substudy: liver fatStudyPhase 2 substudy: body compositionStudyTRIUMPH-1: published phase 3 obesity trial (2026)StudyTRIUMPH-2: published phase 3 obesity and diabetes trial (2026)StudyTRIUMPH-1: Lilly’s 2026 conference presentationRegulatorFDA: concerns with unapproved GLP-1 drugs
Study details, timing & schedule comparisons
Phase 3 · TRIUMPH-1
How the phase 3 steps fit together.
About this phase 3 schedule
This timeline follows Lilly’s reported four-week escalation steps. Participants stopped escalating at their assigned target; the 4 mg group did not follow the entire 12 mg path. Other trials can investigate different schedules.
All amounts below were administered once weekly by subcutaneous injection. The full path to 12 mg included two 2 mg increases followed by two 3 mg increases.
- Weeks 1–42 mgStarting step
- Weeks 5–84 mgTarget for the 4 mg arm
- Weeks 9–126 mgIntermediate step
- Weeks 13–169 mgTarget for the 9 mg arm
- Week 17 onward12 mgTarget for the 12 mg arm
The roughly 28% headline is a group average under a particular analysis, not a reason to pursue the highest amount. Compare the published result and analysis methods ↓
Pharmacokinetics
Why did trials use weekly administration?
The phase 1b study reported a half-life of approximately six days. Half-life is the time for the drug concentration to fall by about half, rather than the time until it disappears. This supports the once-weekly interval studied in trials. Weekly exposures overlap, so levels build over several weeks. A simple half-life calculation suggests approaching steady state after roughly a month at an unchanged weekly amount; changing the amount starts a new adjustment period. The illustration below shows only the decline after one exposure.
Phase 1b paper ↗Illustrative exponential decline after a single exposure. Not an individual blood-level forecast; repeated doses overlap.
Published trial examples · 2023
Amounts and schedules studied in the phase 2 obesity trial
About historical trial arms
These are historical research arms, not an approved dosing plan. The 1 mg arm was not a universal first-month recommendation. Suitability, interactions, side effects and monitoring require clinical assessment.
All arms used once-weekly subcutaneous administration for 48 weeks.
| Trial arm | Starting amount | Escalation context |
|---|---|---|
| 1 mg | 1 mg | Fixed-dose arm |
| 4 mg | 2 or 4 mg | Separate starting-dose groups |
| 8 mg | 2 or 4 mg | Separate starting-dose groups |
| 12 mg | 2 mg | Escalation arm |
Escalation steps were separated by four weeks, for up to 12 weeks. Lower starts partly reduced gastrointestinal adverse events.
Original trial, protocol and safety results ↗Community-reported examples
Lower starts, gradual changes and “lowest effective dose.”
About reported community schedules
These are selected public experiences, not a validated initiation plan or a representative survey. Clinical outcomes, interactions and monitoring matter alongside appetite and reported side effects. Trial schedules and self-directed schedules are different kinds of evidence.
In an August 2026 discussion, several people reported starting at 1–2 mg. One described spending four weeks at 1 mg, then four at 2 mg and four at 3 mg. Others used different intervals or reported nausea even at low amounts. These examples explain the community’s “low and slow” conversation; they do not establish a standard 1 mg increase every month.
“Lowest effective dose” describes a community preference for less hunger and food preoccupation while still being able to eat adequately, with few or no noticeable side effects. That is the balance PeptideLit’s founder also describes from community experience. The aim is manageable appetite, rather than making eating difficult. It is a preference, not a clinically validated dose-selection rule; appetite and tolerability alone do not measure all benefits or risks.
Lower starting amounts and longer holds
PeptIQ’s current guide discusses 0.25 mg community starting charts while distinguishing them from trial arms. The original forum accounts above provide individual weekly examples; they do not establish a safe switch from semaglutide or tirzepatide. Read the unofficial guide ↗
Different intervals and stacked compounds
The TRIUMPH-1 schedule does not validate shortening the interval to four or five days. Giving the same amount more frequently changes exposure; a “microdose” label does not make those schedules equivalent.
Peptide Dosing Protocols describes introducing MOTS-c after four weeks of retatrutide alone, and explicitly notes that this sequence has not been tested in a trial. It is an online stacking proposal with supplier promotions, not evidence of added benefit or safety. Read the stacking proposal and its limitations ↗
Tolerability is part of the story
Nausea, diarrhea and vomiting were among the common gastrointestinal events in the phase 2 trial; lower starting amounts partly reduced these effects. That does not establish that glucagon activity alone explains side effects or differences in community schedules. Trial safety findings ↗
Does a larger body simply need more?
Exposure depends on absorption, distribution and clearance, not just the size of the bloodstream. Retatrutide was engineered for albumin binding and prolonged exposure. The reviewed trial schedules used fixed amounts; they do not supply a body-weight-to-dose conversion.
Molecular design and early pharmacology ↗STUDIES WORTH UNDERSTANDING
How to read a studyBeyond the headline.
Selected studies and clinical reports, with the question, context and limitations close at hand.
Phase 32026
Retatrutide: TRIUMPH-1 phase 3
Could retatrutide improve weight and obesity-related outcomes in a larger trial?
- Participants
- 2,339 adults
- Follow-up
- 80 weeks
Phase 32026
Retatrutide: TRIUMPH-2 phase 3
What happened in people with both obesity and type 2 diabetes?
- Participants
- 1,152 adults
- Follow-up
- 80 weeks
Phase 22023
Retatrutide: the phase 2 obesity trial
Could a peptide acting on GIP, GLP-1, and glucagon receptors reduce body weight in adults with obesity?
- Participants
- 338 adults
- Follow-up
- 48 weeks
Phase 22023
Retatrutide: glucose and weight in type 2 diabetes
Could triple-receptor activity improve glucose regulation as well as body weight?
- Participants
- 281 adults
- Follow-up
- 36 weeks
Phase 2a substudy2024
Retatrutide: a closer look at liver fat
Did liver fat change in participants with obesity and metabolic dysfunction-associated steatotic liver disease (MASLD)?
- Participants
- 98 adults
- Follow-up
- 24-week primary assessment; 48-week study
Phase 2 substudy2025
Retatrutide: fat loss and lean mass
What did DXA scans show about the body composition behind the weight change?
- Participants
- 189 enrolled in substudy
- Follow-up
- 36 weeks
Retatrutide calculator.
About calculator examples
Opening values and worked examples illustrate arithmetic; they are not preparation instructions or recommended amounts. Selecting a compound labels the calculation and does not supply a dose or powder-volume correction.
Enter the documented vial mass, preparation information and target amount to see how mass and volume connect.
An arithmetic example
20 mg in an assumed final 1 mL gives 20 mg/mL. An entered 1 mg corresponds to 0.05 mL, or 5 U-100 units, with 20 theoretical portions before losses.
YOUR CALCULATION WORKSPACE
Open focused view →Three tools. Clear numbers.
01 / YOUR INPUTS
Calculator inputsStarting numbers are worked examples, not recommended doses or preparation instructions. Dose-to-units and units-to-dose views describe the same quantities. The calculator defaults to 1 mL (100 U-100 units) of liquid added as an estimate of total solution volume.In plain EnglishChoose the amount on your vial label, the liquid you added, and the amount per dose you already want to calculate. Type an exact amount or use the slider; neither selects a dose for you.Vial → dose → syringe
CompoundSelect a name to organize your calculation. Names do not set the vial mass, target amount, or volume. NAD+ is a related compound, not a peptide. For blends, enter each component’s mass separately.In plain EnglishThis is the label on your calculation, like naming a folder. Choosing a name does not decide how much material or liquid to use.
Amount in the vialThe total mass of this compound in the vial, not its concentration. Use the mass stated in your source documentation. 1 mg = 1,000 mcg.In plain EnglishThink of mass as the amount of material you started with. Adding liquid spreads that material out; it does not create more of it. A vial marked 5 mg contains 5,000 mcg.
mg
Liquid added to the vialThe starting 1 mL (100 U-100 units) is an editable example. For a general estimate, we use the liquid added as the total solution volume; powder displacement is not included. If your preparation specifies a different final volume, enter it in Advanced. The calculator does not choose a diluent or mixing procedure.In plain English100 units on a U-100 syringe means 1 mL of liquid added; 200 units in total means 2 mL. The starting 1 mL (100 U-100 units) is an editable calculator example, not a mixing recommendation for every product. The simple calculation uses added liquid as an estimate of final volume. A correction needs data for the specific formulation, not just a peptide name. Enter a documented final volume in Advanced when available.
mL
Amount per doseType your exact amount, or adjust the 1–20 mg slider in whole-mg steps or click a labeled value. Type decimal amounts directly in the field. The slider range is a navigation shortcut, not a recommended dose range. Amounts below 1 mg or above 20 mg can be typed directly. Switching mg/mcg preserves the amount.In plain EnglishThe amount in the vial describes the whole batch. This input describes just one portion. For example, if a 5 mg vial makes 20 equal portions, each contains 0.25 mg (250 mcg). Enter the amount from your protocol and the calculator finds the liquid volume for it.
Advanced Volume & syringe settings
Calculation basisA stated concentration is product-specific and refers to the selected blend component. It does not reveal a recoverable fill volume or establish the product’s allowed number of doses. Entering a different compound or blend component clears this concentration.In plain EnglishUse the mg/mL printed on your product label when you have it. Otherwise, you can use a documented final volume or keep the liquid-added estimate.
Syringe capacityOn a U-100 scale, 100 markings equal 1 mL. Capacity changes the displayed scale, not the concentration. These markings are not compound activity units (IU).In plain EnglishCapacity is how much liquid the syringe can hold when full. On a U-100 syringe, 10 units means 0.1 mL, and 100 units means 1 mL. A smaller syringe holds less, but each U-100 unit still means 0.01 mL.
Marked intervalRead the actual graduation spacing on your device. This setting flags values that fall between markings; it does not round the calculation or guarantee measurement accuracy.In plain EnglishThese are the steps between lines on your syringe. Like a ruler, a value can land between two lines. The calculator points that out instead of moving the answer to a nearby line.
02 / YOUR RESULTCalculated
Retatrutide
Estimate · assumes 1 mL added = total volume
U-100 syringe1 mL capacity · 100 unitsSyringe capacityAll unit conversions here use a U-100 scale: 100 units = 1 mL. The selected capacity changes the maximum volume shown, not the concentration. These are volume scale units, not compound activity units (IU).In plain EnglishCapacity is how much liquid the syringe can hold when full. On a U-100 syringe, 10 units means 0.1 mL, and 100 units means 1 mL. A smaller syringe holds less, but each U-100 unit still means 0.01 mL.
- Amount per dose
- 1 mg
- Full doses per vial Doses per vialTotal vial mass divided by the entered dose amount, rounded down to complete doses. This is a theoretical count before handling losses. It may exceed the labeled usable doses because of overfill or discard instructions. A single-dose vial is not reusable just because arithmetic shows more portions.In plain EnglishAn aliquot is just a portion. This is how many full, equally sized portions the mixture could make in perfect conditions, like counting full glasses from a pitcher.
- 5
- Syringe amount per dose Result displayBoth views describe the same calculated volume. U-100 scale units = volume in mL × 100. Changing the display does not change the concentration, target amount, or calculation. This conversion does not apply to other syringe scales or biological activity units (IU).In plain EnglishThe liquid amount stays the same when you switch views. It is like showing the same distance in centimeters or inches: only the number and label change. Here, 0.1 mL is 10 units on a U-100 syringe.
- 20units
- Amount remaining Amount remainingThe selected compound’s vial mass minus the mass in complete doses. This is a theoretical remainder, not a measured or recoverable amount; overfill, dead space, transfer losses and product discard rules are excluded.In plain EnglishAfter counting all the full doses, this is the amount left over on paper. A result of 0 mg means the amounts divide evenly; handling losses can still leave you with fewer usable doses.
- 0 mg
1,000 mcg
Theoretical · before losses
0.2 mL
After 5 full doses
U-100 volume scaleVolume scaleThis illustration shows calculated volume against the selected capacity. It is not a physical measurement tool. The value is not rounded to the smallest marked interval.In plain EnglishThe picture helps you compare the answer with the syringe you selected. It is a drawing, so do not hold a real syringe up to your screen to measure liquid.
Illustration only · calculated value, without rounding
Concentration & remaining liquid
- Concentration ConcentrationMass divided by final solution volume. For a blend, this is the selected component’s concentration.In plain EnglishThink of juice concentrate: the same amount of concentrate in less water makes a stronger mixture. Here, mg/mL tells you how much material is in each 1 mL of liquid.
- 5 mg/mL
- Per U-100 unit Amount per scale unitOne U-100 scale unit represents 0.01 mL. This is the mass of the selected compound in that volume.In plain EnglishEach U-100 unit is a tiny portion of liquid: one hundredth of a milliliter. This number tells you how much material is inside that tiny portion.
- 50 mcg
- Full portions in vial Complete aliquotsTheoretical count of complete portions at the calculated volume. This excludes transfer loss, dead space, and any change in solution volume.In plain EnglishAn aliquot is just a portion. This is how many full, equally sized portions the mixture could make in perfect conditions, like counting full glasses from a pitcher.
- 5
- Theoretical remainder Remaining volumeMass-equivalent liquid remaining after complete portions. This is not a measured fill or recoverable volume. Handling losses, overfill and product discard rules are not included.In plain EnglishThis is a paper-and-pencil remainder: leftover compound mass expressed as liquid. It does not measure what can be recovered from the vial. Losses and product discard instructions can make the usable amount smaller.
- 0 mL
Saved calculations stay on this device.
See the calculation
Concentration = mass ÷ final volume
5 mg ÷ 1 mL = 5 mg/mLVolume = target mass ÷ concentration
1 mg ÷ 5 mg/mL = 0.2 mLU-100 markings = volume × 100
0.2 mL × 100 = 20 unitsComplete portions = floor(vial mass ÷ amount per portion).
Displayed numbers are rounded for readability; the calculation uses unrounded values.
CONCENTRATION → VOLUME
Dosage calculatorUse the documented concentration and an amount you already want to calculate. U-100 units are volume markings, not biological activity units or IU.Convert a known dose.
Already have the concentration? Find the matching mL and U-100 syringe reading.
Need the concentration first? Use the Reconstitution tab.
YOUR CONVERSION
On a U-100 syringe
5units
0.05 mL · 0.25 mg
Volume = target amount ÷ concentration
0.25 mg ÷ 5 mg/mL = 0.05 mLU-100 units = mL × 100Example inputs are editable. The reading is calculated without rounding to a physical graduation.
ONE MEASUREMENT, ANOTHER UNIT
Mass, volume and activity unitsMass and volume are separate dimensions. Converting between them requires a concentration. IU describes biological activity and has no universal conversion to mg or syringe units.Keep the units clear.
Convert mass or liquid volume. U-100 markings always refer to a 100-units-per-mL scale.
YOUR CONVERSION
1 mg equals
1,000mcg
1 g = 1,000 mg = 1,000,000 mcg
For mass → syringe volume, switch to Dosage and enter a concentration.