Ostarine (MK-2866): Before and After Results, Dosage, Side Effects
Disclaimer: Individuals should only use SARMs for research purposes, as they are not FDA-approved and may have adverse effects. Dr. Touliatos is available for consultation should readers have any questions or concerns.
What is Ostarine?
Ostarine is a second-generation selective androgen receptor modulator (SARM), also referred to as Enobosarm or MK-2866.
The objective with the formulation of ostarine and other SARMs is to mimic the anabolic effects of steroids without the harsh side effects. This potentially will ensure a safer and more efficacious treatment for patients suffering from cachexia, osteoporosis, and anemia.
What Are the Origins of Ostarine?
GTx, Inc., a US biotechnology firm, first described and developed MK-2866 in 2001. Since then, phase 1, 2, and 3 clinical trials have evaluated it.
In phase 3 trials, GTx announced that ostarine was unsuccessful in the treatment of breast cancer patients suffering from cachexia. This was due to insignificant improvements in muscular strength, despite increases in muscle hypertrophy.
This has led GTx to cease its pursuit of ostarine for the treatment of cachexia. However, the biotechnology company remains committed to modifying MK-2866 for improved success in the future.
Contents
- 1 What is Ostarine?
- 2 What Are the Origins of Ostarine?
- 3 Is Ostarine FDA-Approved?
- 4 What Are the Benefits of Ostarine?
- 5 What Are the Side Effects of Ostarine?
- 6 Ostarine Before and After 45 Days
- 7 Ostarine Before and After 5 Weeks
- 8 Ostarine Before and After 8 Weeks
- 9 Ostarine Dosage
- 10 Ostarine Cycle
- 11 Ostarine and Cardarine Cycle
- 12 How to Take Ostarine
- 13 Ostarine Reviews: What Are Researchers Observing?
- 14 Frequently Asked Questions
- 15 Ostarine Pros and Cons
Is Ostarine FDA-Approved?
Given its recent creation, the FDA has not approved ostarine for human use. Consequently, sporting organizations such as WADA prohibit its acquisition for cosmetic purposes. It is also illegal to use ostarine for cosmetic purposes, with only scientific research permitted. This has led to SARM manufacturers modifying their marketing strategy, labeling products as research chemicals instead of dietary supplements, effectively capitalizing on this opportunity.
Travis Tygart, CEO of USADA, has stated that he is looking at “legislative options” to remove ostarine and other SARMs from the market.
What Are the Benefits of Ostarine?
1. Muscle Size and Strength
Ostarine works like anabolic steroids by activating the androgen receptor, increasing bone and muscle strength. Ostarine also enhances satellite cell cycle activation, resulting in the fusing of myofibers and increasing myonuclei in the muscles.
Because ostarine only affects certain tissues, it can build lean muscle without the androgenic side effects of anabolic steroids. This prevents benign prostatic hyperplasia (BPH) from occurring.
- In one study on elderly men and women, participants increased their lean body mass by 3% after consuming 3 mg/day of ostarine for 12 weeks (1).
- This is the equivalent of an 80 kg (176 lb) man acquiring 2.4 kg (5.3 lb) of muscle.
Given that the prescribed dosage of 3 mg/day is only a fraction of the dose weightlifters typically administer to improve their body composition, these results are encouraging. The elderly men and women also experienced significant increases in muscular strength, adding 22 lb to their bench press by the 12th week.
2. No Virilization in Women
Women are particularly vulnerable to virilization effects when taking steroidal compounds. Nonetheless, we have determined that ostarine is safe in this context. Elderly women in the above-cited study also experienced no masculinization effects.
3. Fat Loss
Ostarine is an efficacious SARM for cutting because it can increase insulin sensitivity, which leads to subcutaneous and visceral fat loss.
The reduction of visceral fat is a unique attribute of ostarine, in contrast to various anabolic steroids, which can increase visceral fat. This elucidates why some steroid users develop a distended waistline, an indication of elevated visceral fat levels. Nevertheless, ostarine users will experience fat loss throughout the body, particularly in the midsection, reducing overall waist circumference.
Ostarine also possesses positive metabolic effects, increasing calorie expenditure and satiety. Thus, it has direct and indirect lipolytic effects.
In the elderly study, users experienced a 0.6 kg (1.3 lb) reduction in fat mass. However, we have observed additional fat loss in non-elderly users on ostarine when combining it with standard weightlifting and cardiovascular exercise. Thus, being sedentary may inhibit fat loss on ostarine.
Disclosure: We do not permit any form of advertising on Inside Bodybuilding. We monetize our practice through doctor consultations and meticulously selected supplement recommendations, which have yielded exceptional outcomes in our patients.
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What Are the Side Effects of Ostarine?
Dr. Mike Israetel says that SARMs in general have “comparable side effects” to anabolic-androgenic steroids. However, he adds that some SARMs, such as ostarine, may be “safe” and “effective.”
Ostarine does not appear to cause hypertrophy of the prostate; however, it does reproduce several anabolic steroid side effects.
1. Testosterone Suppression
The men in the cited elderly study who took 3 g/day of ostarine for 12 weeks experienced minimal fluctuations in their serum testosterone levels. Some of our patients utilizing more substantial dosages of ostarine have reported standard libido, nocturnal erections, and testicular volume when taking 25 mg/day for 6 weeks.
However, our SHBG tests indicate that ostarine can cause low testosterone levels post-cycle. One user scored 148 ng/dL, compared to an average score of 264-916 ng/dL for his age range. This occurred after taking 20 mg/day of ostarine for a period of 8 weeks.
Thus, based on existing research and our anecdotal evidence, it is reasonable to conclude that ostarine has no significant effect on endogenous testosterone levels when taken in conservative dosages.
However, in elevated dosages, ostarine exhibits a suppressant effect, which may not invariably result in perceivable side effects.
Ostarine is a mild SARM; therefore, complete shutdown of the hypothalamic-pituitary-testicular axis (HPTA) is unlikely. Dr. Nicholas Downey states that in rodents, luteinizing hormone and follicle-stimulating hormone levels remain largely “unaffected” by ostarine. However, he adds that prolactin “may be an issue” in sensitive users utilizing ostarine, due to it being a weak antagonist of the progesterone receptor.
2. Liver Toxicity
In the elderly study, AST and ALT liver markers increased above standard levels in 20% of participants, indicating ostarine’s hepatotoxic potential. Although AST and ALT levels did not rise to a dangerous level, these participants only received a fraction of the dose compared to those who use ostarine for physique-enhancing purposes.
The oral administration of ostarine, which must bypass the liver before becoming fully active, contributes to its hepatotoxicity.
We have found that other SARMs, such as LGD-4033 and RAD-140, also have the potential to cause hepatocellular-cholestatic liver injury (2).
3. Cholesterol Issues
Taking 3 mg/day of ostarine for 12 weeks led to a 27% reduction in HDL cholesterol, which is beneficial for cardiovascular health. This study’s diminutive dosage raises concerns about such reductions.
Thus, ostarine has the potential to increase myocardial infarction risk in the short or long term, even in modest doses.
The oral nature of ostarine and other SARMs may contribute to their adverse effects on HDL and LDL cholesterol levels. This is due to them stimulating hepatic lipase in the liver upon entry, an enzyme known for decreasing HDL and increasing arterial plaque.
4. Gynecomastia and Water Retention
Several SARMs can elevate estrogen indirectly via binding to the androgen receptor. This leaves additional testosterone free and available to convert to estrogen.
Consequently, some of our patients have reported experiencing bloating or gynecomastia when using SARMs, even though the aromatase enzyme is not present. However, on ostarine, we commonly observe a dry appearance in the muscles with minimal extracellular fluid.
Furthermore, improved insulin sensitivity on ostarine also indicates its minimal effect on estrogen, thereby reducing the likelihood of developing gynecomastia.
One of our patients recently had his estradiol levels tested post-ostarine. They recorded 17.4 pg/mL and thus were within a normal range. The average estradiol range is 7.6-42.6 pg/mL.
5. Hair Loss
A few of our patients have reported hair loss or recession during an ostarine cycle, despite the 5-alpha reductase enzyme failing to be present.
The culprit behind androgenetic alopecia is elevated dihydrotestosterone (DHT) levels. Increases in DHT occur indirectly as ostarine competes with users’ natural testosterone when binding to the androgen receptor. In this instance, ostarine is the more potent substance, thus leaving surplus free testosterone to convert to DHT. Although incidents of hair loss on ostarine are infrequent compared to anabolic steroids, androgenetic alopecia remains possible.
Ostarine Before and After 45 Days
- The Reddit user’s results were achieved by taking 20 mg/day of ostarine for 45 days, combined with conventional weight training methods.
- The user lost 3 kg (7 lb) yet appears increasingly muscular. This is due to enhanced muscle definition rather than increased hypertrophy.
Therefore, the scales may not accurately reflect results when taking ostarine due to the simultaneous effects of muscle-building and fat loss. Before and after pictures are therefore crucial when monitoring progress pre- and post-cycle.
Note: In our experience, this user’s results are above average. Coincidentally, he was training more regularly on ostarine, thus contributing to a portion of the muscle tissue and fat loss.
Ostarine Before and After 5 Weeks
- This Reddit user lost 13 lb after cycling ostarine for 6 weeks. He administered 12.5 mg/day during week 1 and 25 mg/day for the remaining 5 weeks.
- He reported no side effects, at least to his knowledge, but experienced a notable amount of fat loss, accompanied by increases in muscle fullness and vascularity.
Note: Eating in a calorie deficit may have contributed to a portion of the fat loss he experienced during his transformation.
He believes ostarine did not aid him in accumulating muscle mass but likely contributed to muscle retention during his cycle. His strength levels remained continuous throughout his 6-week cycle.
Ostarine Before and After 8 Weeks
- This Reddit user lost 23 lb after administering 20 mg/day for 8 weeks.
- He adopted a calorie-deficit diet during his cycle, contributing to substantial fat loss. He does not appear to have added any marked muscle mass, despite vast improvements in muscle definition.
He reported no improvements in strength. However, he credits ostarine for preserving muscle hypertrophy and strength while consuming low calories, specifically 1,800 calories/day.
In terms of side effects, he monitored his liver enzymes and testosterone post-cycle. His ALT liver enzyme score was high, at 57 IU/L. This is approximately 30% higher than maximum average levels.
He also transitioned to a hypogonadal state and was eligible for prescribed testosterone replacement therapy. He reported physiological and psychological decline post-cycle: feeling jaded and experiencing diminished well-being. This is despite the individual not reporting “a high” throughout the ostarine cycle.
We have found ostarine’s results to be comparable to a mild Anavar or Winstrol cycle, with muscle hypertrophy and fat loss occurring synergistically. These three compounds also share similar side effects.
Ostarine Dosage
Ostarine does not have established dosage guidelines due to a lack of FDA approval. However, clinical studies have successfully administered doses of 3 mg, 9 mg, and 18 mg/day.
- Those taking ostarine to enhance their body composition commonly take 10–30 mg/day.
- Women often take the lower value of this range, such as 10 mg/day, in a bid to avoid virilization effects.
Higher dosages of ostarine are believed to further promote muscle hypertrophy, making them efficacious during a lean bulking cycle. Lower dosages primarily enhance fat loss, making them more appropriate for cutting cycles.
We have observed higher ostarine dosages to exacerbate side effects, including:
- Cholesterol values
- Liver values
- Testosterone suppression
Ostarine Cycle
This is a common ostarine-only cycle we have seen utilized by patients for fat loss and muscle retention.
- They administered 20 mg/day of ostarine sublingually for 8 weeks.
Note: Men commonly execute the cycle above. Women typically administer 10 mg/day for 4–8 weeks.
Individuals can cycle ostarine for up to 12 weeks in some cases. However, this is only felicitous if cholesterol, liver, and testosterone values have not excessively deteriorated from the first 8 weeks.
Ostarine can be cycled with other SARMs simultaneously; however, this is not advised due to further elevations of blood pressure and liver enzymes.
Ostarine and Cardarine Cycle
- Ostarine: 20 mg/day for 8 weeks
- Cardarine: 20 mg/day for 8 weeks
Some users commonly stack ostarine with cardarine for more prominent fat loss during cutting cycles.
Cardarine is not a SARM but a peroxisome proliferator-activated receptor delta (PPARD) agonist. Cardarine has a positive effect on insulin sensitivity and fatty acid oxidation.
Research has found cardarine to significantly decrease adipose tissue, both in animal and human studies (3).
Our lipid profiles have shown cardarine to have cardioprotective properties, increasing HDL cholesterol levels (4) and thus potentially reducing elevations in blood pressure from ostarine.
However, Dr. Thomas O’Connor has observed hepatotoxic effects from cardarine based on his observation of patient labs in over 2,000 SARM users. He likens cardarine’s adverse effects on the liver to taking 50 mg/day of Anavar. Thus, stacking cardarine with ostarine is likely to exacerbate liver values.
Cardarine’s recent formulation qualifies it as a research chemical similar to SARMs.
Since cardarine first appeared in scientific research in 2001, its side effects are still unclear.
The concern with cardarine is its carcinogenic risk (5), with long-term animal studies demonstrating an indisputable correlation with its use and various cancers.
The fitness community has criticized these studies for using excessively high dosages. However, even the smallest cardarine dosage proved to be carcinogenic. This includes a 5 mg/kg dose, equivalent to 65 mg for an 80 kg human. Men and women today use this dose for cosmetic purposes. As a result, the safety of cardarine is uncertain, leading to the discontinuation of clinical trials in 2009.
How to Take Ostarine
Ostarine typically comes as an oral solution, dosed at 25 mg/mL, and is taken by mouth.
Users can measure the dose with an eye dropper or syringe before placing it in the mouth.
Researchers can also administer ostarine sublingually, placing the liquid under the tongue for 10-15 seconds before swallowing.
Such placement allows the liquid to contact and penetrate the mucous membrane, creating a more direct and expeditious entry into the bloodstream (6).
This administration methodology also inhibits presystemic metabolism, increasing ostarine’s biological availability.
Ostarine is commonly available in capsule form, with 10 mg of ostarine typically being present in each capsule.
Ostarine Reviews: What Are Researchers Observing?
Researchers in our Facebook group have published the following Ostarine reviews.
I was extremely suppressed after 8 weeks of 20 mg of ostarine. You may not need a PCT, but always have your PCT on hand before you start this. I did this same stack 8 weeks ago, and I felt tremendous with very positive results.
Ostarine is my favorite SARM. In my personal experience, I have tried 10 mg/day to 50 mg/day, and I believe 25 mg is the optimal dose. I suggest getting bloodwork before you start and when you are done. I ran maybe 8 or 9 cycles with no suppression whatsoever, but my last cycle shut me down completely, and my PCT failed to restart my balls. Consider looking into GW-501516 or GW-0742, as Ostarine can negatively impact your cholesterol ratio (but these compounds do a phenomenal job helping to regulate that while promoting fat loss and energy). Ostarine is pretty liver toxic, so I strongly suggest 1,200 mg/day of NAC (and/or TUDCA) to mitigate the elevation in AST and ALT you will definitely experience.
I ran ostarine at 50 mg per day and felt like rubbish. Worse than any other SARM. Everyone is different, though. I never really liked ostarine. Makes me lethargic.
Finished a 12-week ostarine (20 mg) daily 4 weeks ago. I lift weights 2 days a week and train Muay Thai 2-3 days a week. Happy with the results, I gained about 4 kg and some good strength. Ostarine appealed to me because it’s mild, has no back pumps or shoulder pumps, and I never felt shut down.
Using 15 mg a day at the moment, blown away by the strength gains and recomp effects it’s had in as little as 30 days. Very easygoing on lipids too, which easily makes this my favorite SARM.
Frequently Asked Questions
Can Ostarine Cause Bloating?
Several of our patients have reported bloating from ostarine. For some, this ceased after a couple of weeks of supplementation, and for others it persisted until cycle cessation. We have found that anti-estrogen medications can combat water retention and bloating on ostarine and other SARMs.
Is 10 mg of Ostarine Effective?
10 mg/day is the standard dosage utilized by females. It is the lower end of the standard dosage for males, with 30 mg/day being the high end of this range. 10 mg/day is likely to produce fewer side effects compared to larger dosages, with less pronounced anabolism and lipolysis.
What is the Price of Ostarine?
The price of ostarine can vary depending on the source. Higher-quality products are likely to cost more due to increased manufacturing costs and superior purity levels. Below is a list of current liquid ostarine prices:
- Sports Technology Labs: $54.99
- Chemyo: $69.99
- Pure Rawz: $75.95
- Behemoth Labz: $79.95
Should Ostarine Be Taken on an Empty Stomach?
Our patients have taken ostarine with and without food, and there appears to be no perceivable difference in results.
When is the Most Optimal Time to Take Ostarine?
For some users, we have found that taking ostarine in the evening can increase the risk of insomnia. Thus, we typically administer ostarine in the morning and repeat this dosing every 24 hours.
How Long Does It Take to See Results?
Results can typically be observed visually within the first 2 weeks of supplementation. Fluctuations in weight may not be a reliable indicator of results due to simultaneous muscle gain and fat loss.
Can Users Take Ostarine Pre-Workout?
Some users administer ostarine pre-workout for increased intensity. However, if the workout is in the evening and the user is susceptible to poor quality sleep, then they may not take it before exercise. Equally, if a user commonly experiences dyspepsia, otherwise known as an upset stomach, after dosing, they may opt for a different time.
Can Ostarine Cause Diabetes?
No, ostarine does not appear to cause diabetes in clinical literature or in our experience. Research shows that ostarine can decrease fasting blood glucose by 11% (7).
Ostarine Pros and Cons
Pros:
- Fat burning
- Muscle-building
- Strength-enhancing
Cons:
- Some toxic effects
- Not as potent as other SARMs
Ostarine, or MK-2866, exhibits potent fat-burning properties attributed to its positive effects on insulin sensitivity and stimulation of the androgen receptor.
Results in terms of lean muscle, however, are modest and should be considered inferior to more potent SARMs, such as LGD-4033 or RAD-140.
Individuals often underestimate the severity of SARMs’ side effects. Even mild SARMs such as ostarine present toxicity in relation to the heart and liver. Testosterone suppression is also likely to occur, negatively affecting the HPTA. Clomid can accelerate the recovery of the HPTA, shortening the time span of low testosterone symptoms (8).
Ostarine vs. Anavar: How Do They Compare?
Anavar, an oral steroid, may pose fewer risks than ostarine, with several decades of medical research documenting its effects. However, Anavar exhibits similar side effects to ostarine in the following areas:
- Cholesterol alterations
- Raised liver enzymes
- Testosterone suppression
Side effects from Anavar in therapeutic dosages are often unproblematic, hence Anavar’s former FDA-approved status in medicine.
Thus, we find Anavar’s risk-to-reward ratio to be more desirable than ostarine’s, as it yields superior results in terms of fat loss, strength, and muscle hypertrophy.
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Additional Research
- After supplementing with ostarine for 8 weeks, a person developed jaundice and received a diagnosis of centrilobular cholestasis (9).
- After cycling over 74 miles during a 10-week stack of ostarine and cardarine, a person developed an extreme case of rhabdomyolysis. They consumed 20 mg/day of each substance (10).
- A user experienced itching and dark urine following 2 weeks of ostarine use (11).
- A 36-year-old ruptured their Achilles tendon following a couple of 4-week cycles of ostarine and cardarine (12).
- Male and female cancer patients experienced significant muscle growth on ostarine following a 16-week study (13).
- Ostarine had a negative effect on submaximal endurance following 8 weeks of supplementation (14).
- Ostarine exhibited no adverse effects on LDL cholesterol after 8 weeks of supplementation (15).
- Moderate and high ostarine doses increase bone mineral density in female rats following an 8-week study (16).
- 22% of ostarine users report testicular atrophy (17).
- Fatigue, anemia, nausea, and diarrhea were some reported side effects associated with ostarine at doses of 1 mg and 3 mg per day (18).
References
(1) https://ascopubs.org/doi/abs/10.1200/jco.2007.25.18_suppl.9119
(2) https://aasldpubs.onlinelibrary.wiley.com/doi/full/10.1002/hep4.1456
(3) https://www.ncbi.nlm.nih.gov/labs/pmc/articles/PMC4421799/
(4) https://pubmed.ncbi.nlm.nih.gov/22814748/
(8) https://pubmed.ncbi.nlm.nih.gov/19359408/
(9) https://pubmed.ncbi.nlm.nih.gov/34368386/
(10) https://pubmed.ncbi.nlm.nih.gov/34715583/
(11) https://pubmed.ncbi.nlm.nih.gov/35655632/
(12) https://pubmed.ncbi.nlm.nih.gov/33835995/
(13) https://pubmed.ncbi.nlm.nih.gov/23499390/
(14) https://link.springer.com/article/10.1007/s00210-024-03030-w
(15) https://brieflands.com/articles/asjsm-138116.pdf
(16) https://pubmed.ncbi.nlm.nih.gov/29785666/