MK-677 vs Retatrutide

These sit in different classes. MK-677 is a growth hormone secretagogue; Retatrutide is a GLP-1 / incretin agonist. They get compared because of where they overlap, not because they are interchangeable.

The overlap is appetite control. On this site's goal weighting — an editorial priority score, not a measure of effect size — MK-677 rates 5/5 for appetite control and Retatrutide rates 5/5. Outside that overlap they diverge: MK-677 also carries weight for recovery and sleep and muscle growth, Retatrutide for fat loss and metabolic health.

One trap on this pairing: both score highly for appetite control, but they push it in opposite directions. MK-677 is flagged in this dataset as moving it the wrong way, while Retatrutide lists reduced appetite among its side effects. A goal weight measures how hard a compound acts on something, not which way it acts — so this is the one place on the page where a tie is not a tie.

Neither has an evidence edge — both sit at the same tier. MK-677: controlled human trials behind it, without an approval; never approved, and trials flagged higher fasting glucose. Retatrutide: controlled human trials behind it, without an approval; phase 3 is still running, so there is no long-term safety record. Anyone telling you one is clearly better supported than the other is going beyond what is published.

MK-677 is taken by mouth; Retatrutide is a subcutaneous injection. That is the difference most people actually feel: Retatrutide means reconstituting a vial and injecting; MK-677 does not require either. If needles are the deciding factor, this line settles it before any of the rest matters.

Kinetics are not close. Retatrutide has a half-life of 6 days against MK-677's 24 h — roughly 6× — which is why one is dosed once a week and the other once daily. A long half-life means a steadier level and a mistake you cannot take back for days; a short one means timing matters and a bad day washes out fast.

One of these has an end date and the other does not: MK-677 runs 16 weeks, Retatrutide runs no fixed cycle. An open-ended compound is a standing commitment, not a course you finish. Retatrutide also escalates through a titration schedule rather than holding one dose, so its first weeks are not its steady state.

The contraindication lists are not the same: MK-677 flags active malignancy and under 18, which Retatrutide does not; Retatrutide flags MTC or MEN2 history, pancreatitis history, and thyroid disease, which MK-677 does not. If any of those describe you they remove a compound from consideration outright, regardless of everything above.