Safety Profile

MK-677 Side Effects & Safety

MK-677 has the most extensive safety data of any orally-active peptide, from multiple Phase II trials.

Educational content only. This page is compiled from published research for reference and is not medical advice, diagnosis, or treatment. Readers should verify claims against primary sources and consult a qualified healthcare provider before making any health decisions. Full disclaimer.

Side effects by severity

Common4 effects

Increased appetite

>20%

Expected ghrelin-receptor effect; can be substantial.

Fluid retention

Mild edema; related to GH/IGF-1 elevation.

Fatigue

Particularly in first weeks.

Increased blood glucose

Mild HbA1c rise; caution in prediabetes.

Uncommon3 effects

Muscle pain

Related to fluid retention.

Lethargy

Reported in some users.

Numbness/tingling

Carpal-tunnel-like symptoms from fluid retention.

Rare2 effects

Insulin resistance

More likely in predisposed individuals.

Congestive heart failure

Concern in elderly populations; trial populations showed concerning signals.

Contraindications

Congestive heart failure
Active malignancy
Uncontrolled diabetes
Pregnancy

Drug interactions

Insulin and oral hypoglycemics — may require dose adjustment
Corticosteroids — blunt GH response

Special populations

Not FDA approved. Elderly trials raised CHF concerns. Not recommended in pregnancy.

Safety summary

MK-677 is generally well-tolerated in healthy adults but has raised concerns in elderly trials regarding fluid retention and cardiovascular events. Appetite stimulation can be substantial and may undermine weight-control goals.

Frequently asked

Does MK-677 cause insulin resistance?

Chronic GH/IGF-1 elevation can reduce insulin sensitivity. Fasting glucose and HbA1c may rise modestly. Monitor in predisposed individuals.