Weight Loss & Metabolism

What Is Retatrutide? The Triple Agonist Explained (2026)

The investigational GLP-1, GIP, and glucagon drug that posted the biggest weight-loss numbers yet, and what you can actually access today.

By the pru team · Updated July 9, 2026 · 7-minute read

A woman in her forties in athletic wear lacing her sneakers on a sunlit porch before a morning walk — Image: pru

Retatrutide is an investigational weekly injection from Eli Lilly. It's called a triple agonist because it acts on three hormone receptors at once: GLP-1, GIP, and glucagon. In trials it drove some of the largest weight loss ever reported for an obesity drug. It is not FDA-approved and is not available as a legitimate compounded product yet. pru does not currently offer retatrutide until there is a safe pathway for physician oversight and FDA-regulated 503A pharmacies. pru does offer compounded semaglutide and tirzepatide, prescribed by a physician.

What is retatrutide?

Retatrutide is an investigational obesity drug from Eli Lilly. It's a once-weekly injection still moving through clinical trials, so it is not for sale as a legitimate product. People are talking about it because of one thing: the weight-loss numbers in its studies are the highest reported for any obesity drug so far.

How popular is Retatrutide?People search for Retatrutide about 370,000 times a month in the US, one of the most-searched peptides in the US, and search interest is climbing fast (2026 search data). See the Peptide Popularity Report for the full ranking.

The short version: retatrutide hits three hunger and metabolism hormones at the same time, where today's approved drugs hit one or two. That extra reach is the whole story.

Maker: Eli Lilly (the same company behind tirzepatide).
Type: a weekly injectable peptide, taken like other GLP-1 medicines.
Nickname: the "triple agonist" or "triple-G" drug.
Status in 2026: still in trials, and not offered by pru.

Illustrative. Retatrutide is investigational and not offered by pru.

Why "triple agonist" matters

"Triple agonist" means retatrutide switches on three receptors, not one. Each one does a different job. Together they push appetite down and calorie burn up at the same time, which is why the trial numbers ran so high.

GLP-1 receptor: slows the stomach and quiets appetite. This is what semaglutide targets.
GIP receptor: helps the body handle blood sugar and adds to the appetite effect. Tirzepatide adds this one.
Glucagon receptor: the new piece. It nudges the body to burn more energy, not just eat less.

The simple ideaSemaglutide pulls one lever. Tirzepatide pulls two. Retatrutide pulls three. More levers, in the trials, meant more weight lost.

What the retatrutide trials show

Retatrutide's weight-loss data is strong, and it's research, not a promise for any one person. In the Phase 2 trial published in the New England Journal of Medicine in 2023, adults on the 12 mg dose lost about 24.2% of body weight at 48 weeks, versus about 2.1% on placebo. Phase 3 results reported through 2025 and 2026 went higher still.

Study	Top dose	Duration	Average weight change	Source
Phase 2 (NEJM 2023)	12 mg	48 weeks	~24.2% lost	NEJM
Phase 2 placebo group	none	48 weeks	~2.1% lost	NEJM
Phase 3 TRIUMPH-4	up to 12 mg	68 weeks	up to ~28.7% (avg ~71 lbs)	Eli Lilly
Phase 3 TRIUMPH-1 (BMI 35+ extension)	12 mg	104 weeks	up to ~30.3% (avg ~85 lbs)	Eli Lilly

Retatrutide weight-loss data from Eli Lilly trials. Research figures, not an outcome pru promises.

~24%

peak average weight loss, Phase 2 (12 mg dose)

~30%

peak average weight loss, Phase 3 extension

hormone receptors it acts on

~1 in 8

US adults have used a GLP-1 drug

Sources: NEJM 2023; Eli Lilly; KFF 2024. Weight-loss figures are trial averages, not individual promises.

Retatrutide vs. semaglutide and tirzepatide

The useful comparison is receptors and availability. Retatrutide reaches one more receptor than tirzepatide and two more than semaglutide. But it's the only one of the three you can't legitimately get: semaglutide and tirzepatide are available today as compounded, pharmacy-grade options, while retatrutide is still locked inside trials.

Drug	Receptors	Regulatory status	Available at pru
Retatrutide	GLP-1 + GIP + glucagon	Investigational, still in trials	No
Tirzepatide	GLP-1 + GIP	Branded drug is FDA-approved; compounded available	Yes, compounded
Semaglutide	GLP-1	Branded drug is FDA-approved; compounded available	Yes, compounded

How the three compare in 2026.

Want the side-by-side on the two you can actually access? Read semaglutide vs. tirzepatide and retatrutide vs. tirzepatide.

Retatrutide side effects in trials

Retatrutide's side effects look like the rest of the GLP-1 family, with one extra to watch. Most are stomach-related and show up while the dose is climbing. Slow, steady dose steps made them milder in the trials.

Nausea: the most common effect, reported by up to ~60% at the highest dose in Phase 2.
Other gut effects: vomiting, diarrhea, and constipation, mostly mild to moderate.
Skin tingling (dysesthesia): about 7% felt tingling or a pins-and-needles sensation, tied to the glucagon action.
Heart rate: a small average rise, roughly 6 to 7 beats per minute, peaking near week 24 and easing after.

Why titration mattersIn the trials, people who skipped the slow dose ramp had close to double the stomach side effects. Any GLP-1 drug is meant to be started low and raised over weeks under a prescriber's care.

For the full breakdown, see retatrutide side effects.

Can you buy retatrutide right now?

No, not legitimately. As of 2026, retatrutide is not on the list of drugs that licensed 503A compounding pharmacies are allowed to make. That means there is no lawful, pharmacy-grade compounded version. Lilly is expected to file for approval around late 2026 or 2027, so a real product is still years out.

About grey-market vials"Research-grade" or "not for human use" retatrutide sold online by peptide vendors sits outside the pharmacy system. It isn't prescribed, isn't checked by a licensed pharmacy, and can't confirm what's actually in the vial. That's a real safety risk, not a shortcut.

If your goal is starting a GLP-1 now, the practical move is a compounded medicine that's actually available and prescriber-supervised. See where to buy retatrutide for the full reality check, or jump to the weight loss and metabolism options pru offers today.

What this means if you want to start now

Retatrutide is exciting science and a fair thing to watch. It's also not something you can safely act on yet. The version of "start today" that holds up is a proven GLP-1, prescribed and supervised, paired with the daily habits that make any of these drugs work: protein, movement, and sleep. Wanting to get ahead of your metabolic health is a smart instinct, and acting on it now with a proven, supervised option beats waiting on a drug that is still years away.

A woman and man in their fifties walking briskly together through a sunlit park on a bright morning — Image: pru

Curious about starting low on what's available? Read up on GLP-1 microdosing and the best peptides for weight loss.

How pru handles retatrutide

pru does not currently offer retatrutide until there is a safe pathway for physician oversight and FDA-regulated 503A pharmacies. Because it's investigational and off the compounding list, offering it wouldn't be legitimate today. What pru does offer are the compounded GLP-1s that are available and prescriber-supervised today.

A physician reviews your intake and confirms whether a GLP-1 fits you. You select; the doctor confirms clinical fit.
If it's a fit, an FDA-regulated 503A pharmacy fills your compounded, pharmacy-grade medicine.
Live weight-loss options: compounded semaglutide and compounded tirzepatide.
Pricing is a ~$50/month membership, with the peptide billed at cost and itemized. A higher dose costs a bit more, never a member markup. See pricing.

Where it standsWhen a real, approved retatrutide arrives through a legitimate pharmacy, that changes the picture. Until then, pru points you to a GLP-1 you can actually start safely rather than a vial from the grey market. pru exists to make the proactive choice the accessible one, with licensed physicians, pharmacy-grade medicine, and at-cost pricing in one place. Explore the weight loss and metabolism options when you are ready.

Common questions

What is retatrutide in simple terms?

Retatrutide is an investigational weekly injection from Eli Lilly for weight loss. It's a triple agonist, meaning it acts on three hormone receptors at once: GLP-1, GIP, and glucagon. It is still in clinical trials and not for sale.

Is retatrutide FDA-approved?

No. As of 2026 retatrutide is investigational and not FDA-approved. It's in Phase 3 trials, and Eli Lilly is expected to file for approval around late 2026 or 2027, so a marketed product is still years away.

How much weight did people lose on retatrutide?

In the Phase 2 trial published in the New England Journal of Medicine, adults on the 12 mg dose lost about 24.2% of body weight at 48 weeks, versus about 2.1% on placebo. Phase 3 results reported up to roughly 28% to 30%. These are trial averages, not a promise for any individual.

How is retatrutide different from semaglutide and tirzepatide?

It reaches more receptors. Semaglutide acts on GLP-1, tirzepatide adds GIP, and retatrutide adds a third, glucagon, which raises energy use. The trade-off: semaglutide and tirzepatide are available today as compounded medicines, while retatrutide is not.

Can I buy retatrutide right now?

Not legitimately. It's not on the list 503A pharmacies can compound, so there's no lawful pharmacy-grade version. "Research-grade" vials sold online are grey-market, not prescribed or pharmacy-checked, and carry real safety risks.

What are retatrutide's main side effects?

Mostly stomach-related: nausea (up to about 60% at the top dose in Phase 2), plus vomiting, diarrhea, and constipation. About 7% reported skin tingling tied to the glucagon action, and heart rate rose a few beats per minute on average. Slow dose steps made these milder.

Does pru offer retatrutide?

No. pru does not currently offer retatrutide until there is a safe pathway for physician oversight and FDA-regulated 503A pharmacies. pru offers compounded semaglutide and tirzepatide, prescribed by a physician and filled by an FDA-regulated 503A pharmacy.

How does pru keep peptides affordable?

pru runs on an at-cost model. You pay one flat membership, and the medication is passed through at the pharmacy's price with no member markup. Because pru never marks the medication up, we have every reason to push its price down, not up. As pru grows and orders more, we negotiate lower pricing with our partner pharmacies, and those savings go straight to you. Healthcare pricing is usually hidden and inflated; pru is built to sit on your side of it: transparent, at cost, and fighting to make peptides more affordable as we scale.

Do the savings add up if I take more than one peptide?

Yes, and this is where pru's at-cost pricing saves you the most. Because pru never marks the medication up, every vial is priced at cost, so each peptide you add avoids the markup a typical provider builds in. If a physician has you on more than one peptide, or on a stack, that saving repeats on every vial, all under one flat $50 membership instead of a marked-up price on each. The more your protocol includes, the more the difference adds up, which makes doing it the right way a financially responsible choice, not an expensive one.

Sources & further reading

What Is Retatrutide? The Triple Agonist Explained (2026)

What is retatrutide?

Why "triple agonist" matters

What the retatrutide trials show

Retatrutide vs. semaglutide and tirzepatide

Retatrutide side effects in trials

Can you buy retatrutide right now?

What this means if you want to start now

How pru handles retatrutide

Related reading

Common questions

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