Compiled from the published Murphy 1998, Nass 2008, Svensson 1998 trials + r/MK677, r/Peptides, longevity-clinic reports 2015-2026.

First 1-7 days:

• Appetite surge — usually noticeable within 1-3 days of starting. Often described as "ravenous." Some users find this enjoyable (bulking phase, underweight users); most weight-conscious users find it disruptive.
• Mild headache (first few doses, usually resolves in 1 week)
• Daytime fatigue / drowsiness / "weighted down" feeling — very commonly reported; often the dose-limiting subjective effect. Worse with morning dosing; many users shift to nighttime dosing partly to compensate.
• Slight numbness / tingling in fingers or extremities (carpal tunnel-like; GH/fluid-shift related; usually transient)
• Faster onset of sleep + deeper sleep, especially first 2-3 hours (most consistent benefit)

Weeks 1-4:

• Water weight gain ~2-5 lb (sometimes 5-10 lb) — peripheral edema, sometimes facial. Often the most visible sign.
• Sleep depth continues to improve. Vivid dreams. Some users report waking unusually well-rested.
• Body fat % may actually rise in this window because appetite-driven caloric intake exceeds modest fat-oxidation increase.
• Lean mass slowly increases (~1-2 lb in non-trained users, more variable in trained)
• Fasting glucose may rise by 5-20 mg/dL (modest but measurable; bigger in pre-diabetic users)
• Joint comfort improves slightly in some users (collagen / synovial fluid changes)
• Skin/hair quality slightly improves in some users (collagen effect)

Weeks 4-12:

• Body recomposition stabilizes: typical net effect is +2-4 lb lean, +0-2 lb fat (i.e., total weight up but better composition than weight alone suggests, depending heavily on diet/training context)
• Appetite drive may partially habituate but rarely fully — most users still report meaningful hunger increase at 12 weeks
• Daytime drowsiness may persist in a subset; for these users it's a deal-breaker
• HbA1c may rise ~0.1-0.2 (modest but measurable; bigger in diabetic / pre-diabetic users)
• Edema may partially resolve as kidneys adapt, but usually does not fully clear

Months 3-12 (long-term users):

• Body comp benefits plateau; not magical
• Persistent moderate edema in many users
• HbA1c trend continues upward in some users (this is the long-term metabolic concern)
• Sleep depth benefit persists
• Cardiovascular signals (rising RHR, mild BP elevation) appear in a subset

Compared to ipamorelin: MK-677 produces stronger, more sustained body-comp / appetite / water-retention effects but noticeably more side effects (lethargy, edema, glucose impact) and a less physiologic GH pattern. Ipamorelin is the cleaner tool; MK-677 is the bigger hammer.

Compared to CJC-1295 + ipamorelin combo: Both produce sustained IGF-1 elevation. MK-677 offers oral convenience but at the cost of all the ghrelin-receptor side effects (appetite, edema, drowsiness, mild cortisol/prolactin/aldosterone elevation). CJC/ipamorelin is injectable but cleaner side-effect-wise.

Compared to GHRP-6: Both raise appetite. MK-677 is much longer-acting (24h vs. 2h). GHRP-6 produces stronger acute hunger surge; MK-677 produces more sustained baseline hunger. Cortisol/prolactin spillover is bigger with GHRP-6 than MK-677 but neither is selective like ipamorelin.

Compared to anamorelin (FDA-approved in Japan for cancer cachexia): Same receptor target, different molecule. Anamorelin has strong evidence in cancer-cachexia populations. MK-677 has stronger evidence in healthy adults / sarcopenic elderly.

• Tolerance buildup: Theoretical at sustained tonic GHS-R1a agonism (vs. pulsatile dosing's design intent of avoiding desensitization). Empirically, Nass 2008 showed sustained IGF-1 elevation across 2 years without clear tachyphylaxis. Community reports of "wearing off" effect over months-to-years are inconsistent and may reflect placebo regression rather than true desensitization. Real-world picture: probably minimal-to-modest tolerance, but long-term n is small.
• Recommended cycle: Conservative community default is 8-16 weeks on, 4-8 weeks off. No empirical basis. Borrowed from anabolic-cycling logic. The Nass 2008 trial used 2 years continuous without cycle breaks.
• Reset protocol: Stopping MK-677 clears the drug over ~3-5 days (5 half-lives). IGF-1 returns to baseline over ~1-2 weeks. Edema clears over ~1-3 weeks. Appetite drive clears over ~1-2 weeks. No specific reset intervention needed in healthy users.

Synergistic with

• Resistance training + adequate protein: GH/IGF-1 elevation translates to body-composition change only with anabolic stimulus + amino acid availability. Without these, MK-677 produces fluid retention and appetite-driven fat gain rather than recomposition.
• Sleep optimization (V4 sleep stack): MK-677 amplifies natural early-N3 GH pulse. Optimizing sleep upstream amplifies the drug's effect and partly compensates for its drowsiness side effect.
• Adequate hydration + sodium awareness: Edema-managing strategies (slightly lower sodium intake during ramp-up weeks, adequate water) reduce the water-retention burden.
• CJC-1295 (theoretically): GHRH-receptor + GHS-R1a are complementary pathways at somatotrophs. Mechanistically, the combo would produce additive GH pulses. In practice, this combination is rare and not recommended — it pushes total GH/IGF-1 exposure into supraphysiologic territory with stacked side-effect profiles. Pick one approach.

Avoid stacking with

• Ipamorelin / GHRP-2 / GHRP-6 / hexarelin: All target the same GHS-R1a receptor. Adding pulsatile GHRP injections on top of tonic MK-677 is redundant and pushes total exposure into supraphysiologic territory. Choose one approach (pulsatile or tonic) — not both.
• Recombinant human GH (somatropin): Direct exogenous GH suppresses endogenous pulsatile release via IGF-1 feedback — making MK-677's mechanism less useful. Different therapeutic categories. Stacking produces no benefit ceiling and amplified side-effect profile.
• Glucocorticoids / chronic prednisone: Steroid-induced insulin resistance + MK-677 GH-mediated insulin resistance compound multiplicatively. Glycemic risk.
• High-dose insulin / aggressive glucose-lowering protocols without bloodwork supervision: GH counter-regulates insulin; MK-677 sustained GH elevation may transiently raise glucose. Diabetic / pre-diabetic users need close monitoring.
• Aldosterone-active compounds / mineralocorticoid agonists: Would compound the sodium/water retention side effect. Rare overlap in practice.

Neutral / safe co-administration

• Most CNS nootropics in the user's V stack stack: modafinil, citicoline, NAC, magnesium, fish oil, theanine, rhodiola, curcumin, beta-alanine, creatine — no GH-axis collision.
• Caffeine — no interaction.
• Vitamin D3, K2 — no interaction; D3 supports steroidogenesis broadly (orthogonal pathway).
• Most antihypertensives (BP rises mildly on drug; standard meds work normally).
• BPC-157 / TB-500 (peptide recovery stack) — mechanistically separate; combined for systemic recovery in injury-rehab contexts (relevant to the user's elbow thread, but irrelevant since MK-677 is skip).
• Selegiline, bupropion — no known interaction.
• Statins — no significant pharmacokinetic interaction.

• No significant CYP induction/inhibition by MK-677 itself, though it is metabolized partly through CYP3A4 — strong CYP3A4 inhibitors (ketoconazole, ritonavir, grapefruit juice in significant amounts) may modestly increase MK-677 exposure; strong CYP3A4 inducers (rifampin, carbamazepine) may modestly reduce it. Clinically usually inconsequential at typical doses.
• Insulin / oral hypoglycemics — GH is insulin-antagonistic; diabetic patients on insulin or sulfonylureas may need dose adjustment to avoid loss of glycemic control.
• Glucocorticoids — additive insulin resistance.
• Levothyroxine — GH alters thyroid hormone metabolism (T4 → T3 conversion increases); subtle dose adjustment may be needed in hypothyroid patients on stable replacement.
• Hormonal contraceptives (oral estrogen) — oral estrogen blunts hepatic IGF-1 generation in response to GH stimulation; may reduce MK-677's downstream IGF-1 effect. Transdermal estrogen does not.
• Anticoagulants — no direct interaction.
• MAOIs (selegiline, etc.) — no documented interaction.
• Modafinil — no documented interaction.

• GHSR (ghrelin receptor) polymorphisms (e.g., Leu90Val, c.214C>A): Variants modulate receptor function; some carriers have higher baseline ghrelin response and may show different MK-677 pharmacodynamic response. Not clinically tested for dosing.
• GHR (growth hormone receptor) exon 3 deletion polymorphism (~25-50% population frequency): Carriers (d3-GHR) have enhanced GH-receptor signaling and may respond more strongly to a given GH stimulus. Predicts greater IGF-1 response and effect size for any GH-axis intervention.
• IGF1 SNPs (rs7136446, rs5742612, rs35767, rs1520220): modulate baseline IGF-1 levels; carriers of low-IGF-1 alleles may show larger relative response.
• IGFBP-3 promoter polymorphisms: affect bioavailability of free IGF-1 vs. bound IGF-1.
• CYP3A4 polymorphisms (rs2740574, rs35599367): may modestly alter MK-677 exposure in poor / ultra-rapid metabolizers, but clinical significance is small.
• Practical takeaway: No actionable PGx for prescribing decisions in 2026. GHR exon 3 deletion is the most studied modifier of GH-axis response. Track on the user's 23andMe (~June 2026) for completeness — does not change SKIP-FOR-NOW verdict.

Quality concerns with gray-market: Independent SARM/research-chem vendor analyses 2022-2026 have found MK-677 vendor batches with 50-110% of label-claim content, contaminated with related impurities, and occasional substituted compounds. Verify third-party COA (ideally HPLC + mass spec), check purity ≥98%, and consider rotating vendors based on community reputation. Sports Technology Labs and Pure Rawz have been more reliable in independent testing 2023-2026 than the median gray-market vendor.

Practical estimate: ~$30-60 per 1-gram vial / 60-90 caps × 10-25 mg. At 25 mg/day, a 1g supply lasts ~40 days. Roughly $25-50/month at standard dosing.

Sourcing for users in this archetype: Solvable via gray-market research-chem vendors at $30-60/g. Cost is not the gating factor. Verdict is SKIP-FOR-NOW for medical reasons (peak natural baseline, weight-management collision, sustained-tonic vs. pulsatile-physiologic shape problem), not access reasons.

• Baseline (before starting):

  • IGF-1, IGFBP-3 (the primary efficacy + safety biomarkers; target staying within age-appropriate normal range, upper half acceptable, above-range concerning)
  • Fasting glucose, fasting insulin, HOMA-IR, HbA1c (GH antagonizes insulin; MK-677 has documented A-tier glucose intolerance signal — track this carefully)
  • Lipid panel (LDL, HDL, triglycerides, ApoB)
  • Prolactin, AM cortisol (baseline; MK-677 produces modest elevations in both — bigger than ipamorelin, smaller than GHRP-6)
  • Free + total testosterone, LH, FSH, SHBG, estradiol (HPG-axis baseline)
  • TSH + free T4, free T3 (GH affects T4→T3 conversion)
  • ALT, AST, GGT (general hepatic baseline)
  • CBC, BMP (general health baseline)
  • Resting heart rate, blood pressure, body weight (edema baseline — most predictable side effect)
  • BNP / NT-proBNP (only if cardiac risk factors present; signal of fluid-retention-driven cardiac strain)
  • For the user: not applicable — verdict is SKIP-FOR-NOW so no baseline lab additions specifically for this drug. Standard 23andMe + June 2026 bloodwork already captures IGF-1, fasting glucose, HbA1c, lipid panel at baseline.

• During use (months 1, 3, 6, then quarterly):

  • IGF-1 — every 6-8 weeks during titration; target upper-normal range for age; reduce dose if >300 ng/mL
  • Fasting glucose, HbA1c — quarterly (or more frequently if pre-diabetic)
  • Lipid panel — quarterly
  • Body weight, BP, HR — weekly (edema watch)
  • Symptom log — paresthesia, joint pain, headaches, daytime drowsiness, appetite changes, sleep changes, edema visible

• Post-cycle (if cycled):

  • IGF-1 — 4 weeks post-cessation to confirm return to baseline
  • Fasting glucose, HOMA-IR, HbA1c — to confirm reversibility of any insulin resistance shift
  • Body weight + edema markers — confirm clearance (typically 1-3 weeks)