Q1

What is retatrutide?

Retatrutide is a once-weekly injectable research compound from Eli Lilly that acts on three receptors: GIP, GLP-1 and glucagon. It is not approved anywhere yet and is still investigational.

Q2

How much weight did people lose in the phase 3 trials?

At 80 weeks in TRIUMPH-1 (obesity, no diabetes): 19.0% at 4 mg, 25.9% at 9 mg, 28.3% at 12 mg. In TRIUMPH-2 (obesity + type 2 diabetes): 12.7% at 4 mg, 19.1% at 9 mg, 20.8% at 12 mg. Placebo lost 4.0%. In TRIUMPH-1, 45.3% of the 12 mg group lost 30% or more of their body weight.

Q3

What are the TRIUMPH trials?

TRIUMPH is the phase 3 program. TRIUMPH-1 put 2,339 people with obesity but no diabetes on 80 weeks and the 12 mg group lost 28.3%. TRIUMPH-2 put 1,152 people with obesity and type 2 diabetes on 80 weeks and 12 mg lost 20.8%. TRIUMPH-3 covered 1,949 people with severe obesity plus heart disease (22.6% at 12 mg over 80 weeks), and TRIUMPH-4 covered 445 people with obesity and knee osteoarthritis (28.7% at 12 mg over 68 weeks).

Q4

What did the earlier phase 2 trial show?

338 people over 48 weeks. The 12 mg group lost 24.2% of body weight — already ahead of what TRIUMPH-1 later confirmed at week 48 (24.2%).

Q5

How fast does the weight come off?

On 12 mg: 17.5% at week 24, 24.2% at week 48, 28.3% at week 80. Weeks 24 and 48 are from the phase 2 trial, week 80 from TRIUMPH-1. The curve was still dropping at week 48 with no plateau — judge it at months, not weeks, because the first 16 weeks are mostly titration.

Q6

How is retatrutide dosed in the trials?

Every arm started at 2 mg once weekly and stepped up every four weeks: 2 mg weeks 1-4, 4 mg weeks 5-8, 6 mg weeks 9-12, 9 mg weeks 13-16, then the target dose from week 17. Nobody in the 12 mg group reached 12 mg until around week 17, and lower-dose arms stopped climbing at their target. 2 mg was only ever a starting step. No trial kept anyone on 2 mg, so there is no 2 mg result.

Q7

What are the most common side effects?

GI effects (nausea, vomiting, diarrhea, constipation) were the most common, mostly mild to moderate, and concentrated during dose increases — which is why the four-week holds exist. 11-18% quit the 12 mg dose over side effects (11.3% in TRIUMPH-1, 18.2% in TRIUMPH-4; placebo was 4-5%). Lower doses dropped out less: 4.1% at 4 mg in TRIUMPH-1, below placebo.

Q8

What is dysesthesia?

An altered skin sensation unique to this drug class. At 12 mg it affected 7-21% of participants — 7.3% in TRIUMPH-2 and 20.9% in TRIUMPH-4.

Q9

Does retatrutide raise heart rate?

Phase 2 recorded a peak resting heart rate rise of +6.7 beats per minute at 12 mg, highest around week 24 and easing after. Approved drugs in the same class carry label warnings for pancreatitis, gallbladder disease and thyroid C-cell tumors (seen in rodents).

Q10

Is retatrutide approved?

No — it is not approved in any country as of now. The realistic timeline: Lilly files the BLA with the FDA in Q1 2027, standard review adds 10-12 months, making late 2027 the earliest realistic approval.

Q11

How does the reconstitution math work?

10 mg vial + 1 mL bacteriostatic water = 10 mg per mL. On a U-100 insulin syringe, 10 units = 1 mg, so the trial steps map to 20 / 40 / 60 / 90 / 120 units. 120 units is more than a 1 mL syringe holds — a stronger mix avoids splitting: 30 mg vial + 2 mL = 15 mg per mL, so 12 mg = 80 units.

Q12

What should I track while researching it?

Body weight and waist weekly, resting heart rate weekly, plus A1C and fasting glucose, lipid panel, CMP (kidney and liver) and lipase. Get a baseline before starting, then recheck around every three months — those are the markers the trials themselves reported.

Keep reading

• Retatrutide Phase 3 Research Guide — the TRIUMPH-1 and TRIUMPH-2 results on one page: titration, results by dose, reconstitution math.
• Retatrutide price comparison — current listings, price per mg and vendor trust scores.