Ibutamoren (MK-677) Effects and Reviews

By Dr. Dimitar Marinov

medical reviewed by Best HGH Doctors and Clinics dedicated team.

Evidence basedThis article is reviewed by medical professionals for the relevancy and accuracy of the content. Every article is evidence-based and contains references to peer-reviewed studies and academic research.

The growth hormone market is full of products claiming to be as effective as the FDA-approved therapy with human growth hormone (HGH).

One of these products is a growth hormone secretagogue (GHS) called Ibutamoren (code names MK-677 and L-163,191). Sellers present it as a newer, safer, more convenient, and much more affordable therapy for low HGH.

Its popularity stems from the fact that there is no need for daily injections like other GHS or HGH. It’s an oral non-peptide HGH stimulant.

Yet, MK-677 is not FDA-approved, and research about its safety and effectiveness is scarce. In this article, we will break down the evidence so far and weigh in on all pros and cons of Ibutamoren.

What does MK-677 do?

MK-677 belongs to a class of drugs that stimulate the pituitary gland into producing more growth hormone.

What is Ibutamoren (MK-677)?

It is a GHS that mimics the hunger hormone (ghrelin). Ghrelin spikes when you are hungry and triggers the ghrelin receptors in the brain called growth hormone secretagogue receptors (GHS-R).

According to research, activating these receptors will increase your appetite, but also stimulate the pituitary gland to produce HGH which helps counteract low blood sugar while fasting.

Thus, MK-677 triggers the GHS-R by mimicking ghrelin and stimulates natural HGH production. Animal studies report that GH levels rise 30-40 minutes after oral administration of Ibutamoren and the effect continues for several hours.

What’s the optimal MK-677 dosage?

Considering the fact that MK-677 is not officially approved for human use, there also isn’t an official dosage recommendation. Yet, most human trials on Ibutamoren report using doses between 10 to 50 mg taken once daily.

The most common dose used in the majority of the trials, including the longest trial that lasted for 2 years, is 25 mg of Ibutamoren a day.

25 mg is also the most common dose used by bodybuilders who take MK-677 illegally in an attempt to increase their muscle mass gains. Beginners usually start with a lower dose of 10-15 mg a day and then gradually increase it.

The same 10-15 mg dosage is often purported to result in fat loss, although there is no evidence that Ibutamoren can help with fat burning or weight loss.

Taking high doses of MK-677 may increase the risk of the most commonly reported side effects, such as increased appetite, hyperglycemia, high blood pressure and insulin resistance.

The adverse reactions and potential toxicity of overdosing on Ibutamoren are unknown

While some trials do not show any serious adverse reactions, others have reported serious conditions such as congestive heart failure among older adults, even with doses of 25 mg a day.

Moreover, some researchers express concerns that prolonged use of Ibutamoren may also increase sensitivity to chronic stress.



MK-677, aka ibutamoren, is the only orally bioavailable growth hormone secretagogue (GHS) that effectively boosts growth hormone (GH) levels. 

Increase muscle growth

Improve sleep

Lower cholesterol (LDL) levels

How long does MK-677 stay in your body?

According to studies, MK-677 has an elimination half-life of about 6 hours, which is why it can be taken once a day.

Considering the fact that it takes 4-5 half-lives until a substance is completely eliminated from the human body, MK-677 would stay in your system for about 24-30 hours.

During this period, research reports that Ibutamoren is detectable in the blood as well as in the urine, as growth hormone secretagogue has mostly urine excretion. MK-677 is also banned by the World Anti-Doping Agency (WADA), and it can be detected via drug tests.

How long does it take to see results from MK-677?

Taking MK-677 can stimulate your ghrelin receptors and cause an increase in HGH synthesis within an hour.
First MK-677 results occur in 2 weeks

However, studies report that it takes 2 weeks until there is any measurable effect on the body (such as body composition changes) and up to 2 months before the effect becomes noticeable.

In clinical settings, the studies usually report that Ibutamoren was administered in the morning. Yet, most bodybuilders take ibutamoren at night in order to avoid the increase in hunger which would otherwise affect their appetite throughout the whole day.

Research shows that the long-term effects of MK-677 include the following:

  • increase in lean body mass
  • higher limb fat
  • reduction in LDL
  • increased bone mass
  • elevated cortisol levels

What happens when you stop taking MK-677?

Discontinuing MK-677 hasn’t been associated with any side effects. HGH and IGF-1 levels return to the pre-therapy levels, and there is no withdrawal.

Most bodybuilders and other athletes who use MK-677 illegally cycle on and off, although there is no scientific evidence to suggest that. Ibutamoren does not have any suppressive effects on the endocrine system, and there is no need for post-cycle therapy (PCT).

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What are the proven benefits of MK-677?

MK-677 users share that they have experienced benefits such as improved recovery from training, improved muscle pump, and better sleep.

Many of them also took it in an attempt to heal sports traumas. Some users suggest that it helped them recover their joints and tendons after training injuries, much like BPC-157.

MK-677 is mainly investigated for the treatment of growth hormone deficiency (GHD) and muscle wasting. According to a trial in 32 healthy elderly people, ibutamoren leads to a 55% increase in IGF-1 levels at 2 weeks and 88% by 4 weeks.

Increase in IGF-1 and HGH levels from Ibutamoren

However, only one study has investigated its effectiveness in patients with GHD. Young adults with childhood-onset GHD took 50mg of MK-677 for 4 days. The participants achieved IGF-1 levels comparable to the reference values for healthy elderly individuals.

A study in younger obese individuals found that 2 months of oral treatment with the GH secretagogue MK-677 resulted in an increase in muscle mass of approximately 3 kg and a transient increase in basal metabolic rate. The scientists reported no significant changes in fat mass in the initial study or the follow-up.

The previously mentioned 2-years long trial with 65 elderly people reported 5-7 lbs. of weight gain for the whole period of the study. There were no changes in fat mass or muscle strength despite the increase in HGH secretion.

There are currently no studies investigating the effect of MK-677 on muscle wasting and cachexia

MK-677 also led to a slight reduction in LDL levels and an increase in bone mineral density. However, no significant functional improvements have been reported in patients with bone fractures.

In addition, some healthy people who took Ibutamoren reported improved deep sleep and decreased sleep latency.

What are the most common side effects of Ibutamoren?

The most commonly reported side effect of MK-677 is an increase in appetite, which is a result of triggering the ghrelin receptors. However, the effect appears to be transient and decreases with prolonged use.
The most common side effect of MK-677 is increased appetite
Ibutamoren also leads to transient elevation of cortisol, prolactin, and leptin levels, while thyroid hormones increase after 1-2 months of therapy. Furthermore, it may lead to decreased total testosterone (T) without affecting free T levels.

According to the long-term trial in healthy older adults potential side effects of MK-677 include:

  • muscle pain
  • water retention
  • increased blood sugar
  • increased insulin resistance

Due to its illegal status, there is also a high chance of counterfeit, diluted, and contaminated products. In fact, most illegal sellers wrongly label it as a SARM (selective androgen receptor modulator) – a class of drugs with similar anabolic properties to anabolic steroids, and many mistakenly consider HGH to be a steroid (which they are not).

Can MK-677 cause heart problems?

Currently, only one trial has reported any cardiovascular side effects during Ibutamoren use.

In this trial, all patients were aged over 60 years. MK-677 led to a significant increase in systolic and diastolic blood pressure in the 62 individuals treated with Ibutamoren, compared to the 61 people given a placebo.

Four patients in the treatment group developed congestive heart failure, compared to only one in the control group. Elevated blood pressure is likely one of the main risks that led to the complication.

Elevated blood pressure is also a risk factor for myocardial hypertrophy and an enlarged heart. However, there is no evidence that Ibutamoren can cause heart enlargement.

Despite the negative effect of MK-677 on blood pressure and the potentially elevated risk of heart failure during its use, growth hormone secretagogue does not raise cholesterol levels. On the contrary, Ibutamoren tends to lower the levels of bad cholesterol “LDL.”

Can MK-677 Cause Brain Damage?

Long-term use of Ibutamoren leads to chronic activation of the ghrelin receptors which may pose risks to brain health according to some researchers.

The concerns are based on animal research that suggests that chronically increased activation of the ghrelin receptors may have negative effects on the brain’s tolerance to stress.

According to the researchers, the animals exposed to chronically elevated ghrelin levels experienced fear-enhancing effects.

Yet, clinical studies do not report any increased levels of stress or anxiety among human participants.

Furthermore, animal studies report that MK-677 may enhance neurogenesis in a part of the brain called the hippocampus. However, in a rat model of Alzheimer’s disease, growth hormone secretagogue failed to show any protective effect.

Does MK-677 cause erectile dysfunction?

Researchers reveal that Ibutamoren is a non-selective secretagogue that also increases prolactin and cortisol levels. Elevated levels of prolactin can have a negative effect on libido in both men and women.

Furthermore, hyperprolactinemia may also cause infertility and erectile dysfunction in men.

Yet, the current clinical research, which is mostly conducted amongst the elderly population, does not report increased levels of sexual dysfunction or infertility compared to a placebo.

Does MK-677 cause hair loss?

There are no clinical trials of Ibutamoren to report any change in skin thickness, hair growth, or hair loss during the therapy.

However, research shows that Ibutamoren can increase IGF-1 levels significantly, which in turn may have some benefits for hair growth. Higher IGF-1 levels may speed up hair growth, and its stimulating effect on collagen synthesis may also improve hair strength.

Similarly, the benefits of MK-677 on collagen synthesis may also result in increased skin thickness.

Does MK-677 make you bloated?

Ibutamoren causes water retention due to the increase in HGH levels. This can lead to edema of the limbs, such as swollen hands and feet.

According to research bloating and water retention affects about 2% of participants at 25 mg of Ibutamoren a day. The incidence of bloating will likely increase with higher doses.

Ibutamoren may also cause bloating due to increased food intake. This may occur due to the appetite-stimulating effects of MK-677.

The combination of increased IGF-1 levels, water retention, and increased food intake may also increase the risk of a condition called “bubble gut”, which is common among bodybuilders taking multiple PEDs.

The condition is also known as Palumboism or “pregnant abs,” as the affected individuals are professional bodybuilders with extremely lean physiques, but their abdomens appear bulging and dilated.