The short answer: yes. In the phase 2 obesity trial, retatrutide raised resting heart rate in a dose-dependent way. It peaked around week 24 and then came partway back down. At 48 weeks the top dose was still about 6 beats per minute above where people started, against almost no change on placebo.
That's in the same range as the approved GLP-1 drugs, a little above tirzepatide on average. What nobody has published in a form you can read yet is the phase 3 heart rate data, or what it means for the heart over years.
Status as of October 30, 2026: Retatrutide is not approved by the FDA or any regulator. Every trial number below comes from Lilly's own drug, given under trial monitoring. Nothing here is medical advice or a dosing guide.
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Does retatrutide increase heart rate?
Yes, in the trial data that has been published. The phase 2 obesity paper put it plainly: "Dose-dependent increases in heart rate peaked at 24 weeks and declined thereafter" (NEJM, 2023).
This post goes deep on that one side effect. For the full list (gut effects, skin tingling, blood pressure, hair loss), see is reta safe?
How much does reta raise heart rate?
At 48 weeks in phase 2, about 2 to 6 beats per minute, depending on the dose. Here are the average changes from baseline, as extracted from the trial by a 2026 meta-analysis (Zhang et al., Eur J Med Res, 2026):
Phase 2 group (48 weeks) | Average change in heart rate |
|---|---|
Placebo | +0.4 bpm |
Retatrutide 1 mg | +1.7 bpm |
Retatrutide 4 mg | +3.1 bpm |
Retatrutide 8 mg | +4.8 bpm |
Retatrutide 12 mg | +6.0 bpm |
People started at around 69 to 74 bpm on average. On the top dose, the group average went from about 69 to about 75.
Three caveats:
These are averages. The spread was wide (a standard deviation of about 9 bpm in the 12 mg group). Some people rose a lot more, and some didn't rise at all.
This is the week 48 number, not the peak. The paper says heart rate peaked at 24 weeks. The peak size isn't in the abstract, and the full paper is behind NEJM's paywall. The bpm figures floating around online (6.7, 9, "5 to 11") don't agree with each other, and I couldn't check any of them against the paper.
It's one trial of 338 people. The big phase 3 trials (TRIUMPH-1 with 2,339 people, TRIUMPH-2 with 1,152) don't report heart rate in their abstracts, and the full papers are paywalled (NEJM, Sept 29, 2026; Lancet, Sept 29, 2026).
The phase 2 trial in type 2 diabetes doesn't report heart rate in its abstract either (Lancet, 2023). I couldn't read the full text, so there's no diabetes number here.
When does reta heart rate peak, and does it go back down?
It peaked around week 24 in phase 2 and then declined, but it hadn't returned to baseline by week 48. The +6.0 bpm at 12 mg is what was left after the decline.
The abstract doesn't say why it peaked when it did. One thing worth knowing: most groups started low and stepped up on a fixed schedule, so the dose was still climbing in the early months. That's my read of the design, not a finding. The phase 3 trials used a fixed dose-escalation schedule too (TRIUMPH design paper, Diabetes Obes Metab, 2025).
What the trials can't tell you yet: whether heart rate drifts back to normal over two or three years, and what happens after someone stops. Neither has been published.
Does retatrutide increase heart rate more than tirzepatide?
A little, on average, but less than you might expect. The best comparison comes from the same 2026 meta-analysis, which pooled placebo-controlled trials in people without diabetes and measured every drug the same way (Zhang et al., 2026). The FDA labels add each approved drug's own numbers.
Drug | Average heart rate rise vs placebo | Source |
|---|---|---|
Retatrutide (phase 2, all doses pooled) | +3.5 bpm | Meta-analysis, 2026 |
Retatrutide 12 mg | +5.5 bpm | Meta-analysis (network estimate) |
Semaglutide 2.4 mg (Wegovy) | +3.4 bpm | Meta-analysis, 2026 |
Tirzepatide (Zepbound) | +2.1 bpm | Meta-analysis, 2026 |
Orforglipron (Foundayo pill) | +7.3 bpm | Meta-analysis, 2026 |
Wegovy label | +1 to 4 bpm | FDA label, June 2026 |
Zepbound label | +1 to 3 bpm (vs no increase on placebo) | FDA label, Aug 2026 |
Label sources: Wegovy prescribing information, Zepbound prescribing information.
How to read that:
Pooled, retatrutide looks like semaglutide. The top dose looks higher than both.
The biggest number on the list is a GLP-1 pill, not retatrutide. Orforglipron came out highest in the analysis.
It's still cross-trial. Retatrutide's numbers come from one 338-person trial. The head-to-head against tirzepatide (TRIUMPH-5) hasn't reported.
The two labels treat it differently. Wegovy has a "Heart Rate Increase" warning. It says 26% of adults on Wegovy had a rise of 20 bpm or more at some visit, against 16% on placebo, and it tells prescribers to stop the drug "if patients experience a sustained increase in resting heart rate." Zepbound lists its 1 to 3 bpm only under adverse reactions, with no separate warning. What retatrutide's label will say is up to the FDA after Lilly files.
Why does retatrutide raise heart rate?
Because two of its three targets can speed up the heart, through different routes. Retatrutide activates GIP, GLP-1 and glucagon receptors. Tirzepatide hits only the first two.
GLP-1. A study of monkey and human tissue found GLP-1 receptors in the cells of the sinoatrial node, the heart's natural pacemaker (Pyke et al., Endocrinology, 2014). In mice, GLP-1 drugs raised heart rate "through multiple mechanisms," largely through the nervous system rather than the heart acting alone (Baggio et al., Mol Metab, 2017).
Glucagon. In isolated mouse pacemaker tissue, retatrutide sped up the beating rate. A drug that blocks the glucagon receptor stopped it, while a beta-blocker didn't. The authors concluded retatrutide "excites the beating rate ... via GCGR," the glucagon receptor (Neumann et al., 2025).
Human heart tissue. In atrial tissue from heart-surgery patients, retatrutide made the muscle contract harder, and blocking any of the three receptors reduced the effect (Neumann et al., 2025). The same team says plainly they "cannot conclude that retatrutide acts on sinus node cells in the human heart."
A reflex. The mouse paper also offers a simpler route: if the drug relaxes blood vessels, the heart may speed up to compensate. Low blood pressure was more common on retatrutide than placebo in TRIUMPH-2 (Lancet, 2026).
So the glucagon arm is a plausible reason retatrutide might push heart rate higher than tirzepatide. It's lab and animal evidence, not proof in people.
Does retatrutide cause palpitations?
The trials haven't published a palpitations rate. The phase 2 paper did count "cardiac arrhythmia" events, a broad bucket of extra beats and conduction changes. These were mostly mild to moderate. There was one severe case, a prolonged QT interval in someone taking the anti-nausea drug ondansetron (NEJM, 2023). The percentages are in is reta safe?
Palpitations show up in reports from people using it outside trials (below). That's a different kind of evidence, and Wegovy's label is a useful model here: it tells patients to tell their doctor about "palpitations or feelings of a racing heartbeat while at rest."
Does reta affect heart rate variability?
No published retatrutide trial reports HRV. Searchers ask about it a lot, probably because wearables track it. The only data point I found is from social media: 0.6% of users in the study below mentioned decreased HRV (JAMA Netw Open, Oct 14, 2026). That's not a measurement.
What did the trials do about the heart rate increase?
They watched for it, screened out higher-risk people, and set up a dedicated heart trial.
Monitoring. The phase 3 safety checks "include physical examinations, pulse, electrocardiograms and laboratory assessments" throughout (TRIUMPH design paper).
Screening. The phase 2 obesity trial excluded anyone with a heart attack, stroke or heart-failure hospitalization in the prior 3 months, and anyone with uncontrolled high blood pressure (ClinicalTrials.gov, NCT04881760).
Slow dose increases. Doses went up on a fixed schedule, so most people didn't start at their full dose.
A trial in people with heart disease. TRIUMPH-3 enrolled 1,949 adults with severe obesity and established heart disease. Major heart events were rarer than expected, so the hazard ratios came with wide ranges on both sides of no effect (Lilly, July 23, 2026).
The real answer, later. TRIUMPH-Outcomes, about 10,000 people, will test heart and kidney outcomes. It's estimated to finish in February 2029 (ClinicalTrials.gov, NCT06383390).
None of the phase 3 press releases I checked mention heart rate at all, including this week's head-to-head against Ozempic.
What do people taking reta outside trials report?
Heart rate is one of the most-mentioned effects. A JAMA Network Open study used AI to read Reddit posts from 13,589 people who said they were taking retatrutide. Among the 7,823 who described at least one symptom, 4.8% mentioned increased heart rate, 3.8% tachycardia (a fast heart rate) and 1.9% palpitations (Sehgal et al., JAMA Netw Open, Oct 14, 2026).
The authors are careful. They say the pattern may reflect "product or dose variability, peptide stacking ..., reconstitution practices, or misattribution," and call it "hypothesis-generating." Nobody in that study could verify what product or dose they were taking.
BHN ran a small reader survey this month: 38 readers, self-selected, not a study. Of the 26 who named retatrutide as their main compound, 10 said they noticed a higher heart rate. Only appetite loss came up more often (16). One reader said retatrutide from three different labs gave three different results and side effects. That's a reminder that a trial number only describes Lilly's drug. Why vials vary is in how to test peptides for purity.
If you have a heart condition, or take medication for heart rate or blood pressure, the trial data is the conversation to have with your doctor. A baseline before anything changes makes that conversation easier: why bloodwork comes first.
The short version
Retatrutide raised resting heart rate in the trials, more at higher doses.
In phase 2 it peaked around week 24, then eased, and the top dose was still about 6 bpm up at week 48.
On average that's close to semaglutide and a little above tirzepatide, from cross-trial data.
Two of its three receptor targets can speed the heart. Glucagon is the one tirzepatide doesn't have.
No phase 3 heart rate numbers, HRV data or long-term heart outcomes are publicly readable yet. The outcomes trial is due in 2029.
Did your resting heart rate change on reta, and did it settle? Reply and tell me when you noticed it and what your watch showed, rather than what you guessed. If enough of you track it, that's the closest thing to a phase 3 supplement any of us can read.
Want the one-page version of what's approved, what's legal and what's actually been tested? Get the free BHN cheat sheet.