A free timeline of when real trials measured results. No doses, no guessing.
By the Peptide Science Desk Editorial TeamFact-checked against FDA and official sources · Not yet reviewed by a licensed clinician. How we check facts
In STEP 4, people who switched to placebo after 20 weeks gained back 6.9% of their weight by week 68. Source
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
In SURMOUNT-4, people switched to placebo after 36 weeks gained back 14.0% of their weight by week 88. Source
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
These are results from the tested drug in trials. Products sold online as "reta" are not the tested drug.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
The label says it is not a weight-loss drug.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
It is used as needed before sex, not every day. The trials measured results over 24 weeks.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
21 months was the middle (median) length of the study.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Results were measured at 4 and 8 weeks. Many collagen studies are paid for by the companies that sell it.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
This shows hormone levels, not muscle, fat loss or better sleep. No trial tested those.
Hormone levels are not results you can feel.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
This shows hormone changes. It does not prove kisspeptin treats low testosterone.
Hormone levels are not results you can feel.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Do not start, stop or change a medicine on your own. Ask your doctor what to expect for you.
Weeks from the first dose until the main result was measured. A longer bar is not worse. It is just when the study looked.
Collagen peptides (skin)Food supplement, 69 women
PT-141: Vyleesi (bremelanotide)RECONNECT, 1,267 women
Retatrutide, phase 2 main result (in testing)Phase 2, 338 adults
Egrifta SV (tesamorelin)412 adults with HIV
Imcivree (setmelanotide)38 people, rare disease
GLP-1: Saxenda (liraglutide)SCALE, 3,731 adults
GLP-1: Wegovy (semaglutide)STEP 1, 1,961 adults
GLP-1: Zepbound (tirzepatide)SURMOUNT-1, 2,539 adults
Tymlos (abaloparatide)ACTIVE, 2,463 women
Forteo (teriparatide)1,637 women
BPC-157, TB-500, ipamorelin, KPV, MOTS-c and blends like KLOW have no trial in people that measured how long they take to work.
| Medicine (trial) | Weeks |
|---|---|
| Collagen peptides (skin) Food supplement, 69 women | 8 weeks |
| PT-141: Vyleesi (bremelanotide) RECONNECT, 1,267 women | 24 weeks |
| Retatrutide, phase 2 main result (in testing) Phase 2, 338 adults | 24 weeks |
| Egrifta SV (tesamorelin) 412 adults with HIV | 26 weeks |
| Imcivree (setmelanotide) 38 people, rare disease | 52 weeks |
| GLP-1: Saxenda (liraglutide) SCALE, 3,731 adults | 56 weeks |
| GLP-1: Wegovy (semaglutide) STEP 1, 1,961 adults | 68 weeks |
| GLP-1: Zepbound (tirzepatide) SURMOUNT-1, 2,539 adults | 72 weeks |
| Tymlos (abaloparatide) ACTIVE, 2,463 women | 78 weeks (18 months) |
| Forteo (teriparatide) 1,637 women | ~91 weeks (21 months) |
Weight loss and bone strength build slowly. That is why big trials ran for a year or more.
GLP-1 drug doses are also raised slowly at the start to cut stomach side effects, so the full effect comes later.
It means we found no published study in people that tested the peptide for that use. There is no honest answer to "how long does it take" yet.
No human data does not prove a peptide works or does not work. It means nobody has checked in people. It also says nothing about safety, which we rate separately.
No. CJC-1295 raised growth hormone for days after one shot. Kisspeptin raised sex hormones for hours to days. But no trial showed more muscle, less fat or better sleep.
| Peptide | First result we found | FDA status |
|---|---|---|
| GLP-1: Wegovy (semaglutide) | 20 weeks | FDA approved |
| GLP-1: Zepbound (tirzepatide) | 36 weeks | FDA approved |
| Retatrutide | 24 weeks | In testing |
| GLP-1: Saxenda (liraglutide) | 56 weeks | FDA approved |
| Egrifta SV (tesamorelin) | 26 weeks | FDA approved |
| PT-141: Vyleesi (bremelanotide) | 24 weeks | FDA approved |
| Imcivree (setmelanotide) | 52 weeks | FDA approved |
| Forteo (teriparatide) | about 21 months | FDA approved |
| Tymlos (abaloparatide) | 18 months | FDA approved |
| Collagen peptides (food supplement) | 8 weeks | Food supplement |
| CJC-1295 | 6 to 11 days | Not FDA approved |
| Kisspeptin | hours to days | Not FDA approved |
| BPC-157 | No real trial | Not FDA approved |
| Selank | No real trial | Not FDA approved |
| Ipamorelin | No human data | Not FDA approved |
| TB-500 | No human data | Not FDA approved |
| KPV | No human data | Not FDA approved |
| MOTS-c | No human data | Not FDA approved |
| KLOW blend (GHK-Cu, BPC-157, TB-500, KPV) | No human data | Not FDA approved |
For FDA-approved peptide medicines, trials checked results after weeks to months: 24 weeks for Vyleesi, 26 weeks for Egrifta SV, 56 to 72 weeks for GLP-1 weight-loss shots. For BPC-157, TB-500 and most peptides sold online, there is no trial in people that measured it.
Nobody knows. There is no real trial in people. One clinic asked 16 people with knee pain how they felt months after a shot, with no comparison group.
In STEP 4, people lost 10.6% on average by week 20 of Wegovy (semaglutide). In SURMOUNT-4, people lost 20.9% by week 36 of Zepbound (tirzepatide). Results differ a lot from person to person.
In two trials, people who switched to a placebo gained back a lot of the weight within a year: 6.9% on average after stopping Wegovy and 14.0% after stopping Zepbound. Never stop or change a medicine without your doctor.
We never give doses. Your doctor and the FDA label decide the dose. This tool only shows when trials measured results.
From published trials on PubMed. Each time point links its source. Checked October 27, 2026.
