Retatrutide

Retatrutide produces large weight loss but the safety data is still phase 2, and the heart rate and arrhythmia signals deserve real scrutiny before anyone calls this a settled drug.

Retatrutide is a triple agonist drug that activates GLP-1, GIP, and glucagon receptors. The evidence comes from two phase 2 trials funded by Eli Lilly, the manufacturer [2]. In the obesity trial, 338 adults lost 8.7% to 24.2% of body weight over 48 weeks depending on dose, compared to 2.1% on placebo [2]. In the diabetes trial, 281 adults saw HbA1c drop by up to 2.02 percentage points over 24 weeks [2]. A 2025 network meta-analysis of 12 trials found retatrutide produced about 23.8% mean weight loss versus 16.8% for tirzepatide, but with a relative risk of adverse events of 4.1 compared to placebo, versus 2.78 for tirzepatide [5].

The safety signals are what matter here. In the obesity trial, heart rate increased by 5.6 beats per minute on retatrutide [2]. Arrhythmias occurred in 4% to 14% of retatrutide patients versus 2% to 3% on placebo [2]. Discontinuation rates ran 16% to 17% across both trials [2]. A 2026 meta-analysis of phase 3 data reported 12% discontinuation due to adverse events at the 8 mg dose and noted neurosensory dysesthesia as a new signal [4]. The phase 3 TRIUMPH program is still running, with cardiovascular and renal outcome results expected after late 2025 [6]. No long-term safety data beyond 48 weeks exists in the published record.

My call: retatrutide produces substantial weight loss and glycemic improvement, but the safety data is incomplete, the heart rate and arrhythmia signals are concerning, and the phase 3 cardiovascular outcomes are not yet published. Confidence: low for long-term safety, moderate for short-term efficacy.