Bimagrumab_
Also known as BYM338
An experimental shot that strips fat while adding muscle.
Common vial size is what vendors typically sell, not a recommendation. Enter your own vial in the calculator.
What is Bimagrumab?
Plain language first. The technical label stays, but it never stands alone.Overview
Bimagrumab is a monoclonal antibody that blocks the activin type II receptor, a signal that normally limits muscle. In plain terms: by releasing that brake it builds muscle while the body sheds fat, an unusual combination being studied with GLP-1 drugs. It is still experimental.
What it's used for
An unusual experimental shot that strips fat while adding muscle, by blocking a signal that limits muscle. It is being studied alongside GLP-1 drugs.
How does Bimagrumab work?
What it does in the body, and where.Bimagrumab is not a weight-loss drug in the usual sense. It changes what you lose rather than how much.
- 01It blocks the activin type II receptorThat receptor carries the signal that normally limits how much muscle you build. Blocking it releases the brake.
- 02Muscle grows while fat is lostAn unusual combination. Most weight loss, including from GLP-1 drugs, takes muscle along with fat.
- 03It is being tested alongside GLP-1 drugs, not instead of themThe interest is in pairing it with semaglutide so the weight lost is fat rather than lean tissue.
- 04Dosed by body weight, into a vein10 to 30 mg per kilogram by infusion, which is a very different proposition from a weekly self-injection.
- 05InvestigationalPhase 2 only.
Where this compound is thought to act.
What else is it used for?
Each use below carries its own evidence level. Approved means regulators have cleared it for that purpose. Investigational means it is in trials. Early research means it is being studied and is not established.
- Losing fat while gaining muscle, an unusual combination being studied alongside the GLP-1 drugsInvestigational
- Muscle-wasting conditions, where an earlier trial failed to show functional benefitInvestigational
How much, and do you cycle it?
The range, and whether you take breaks.10 up to 30 mg/kg per month (trial doses), monthly. Not cycled. Infused every 12 weeks in the trialsTrial dose
The dosing interval is long because the antibody lasts a long time, not because anyone is cycling it. The phase 2b trial ran 48 weeks blinded with a further 24 weeks open label.
How do I dose and price it?
Enter your vial and your dose. Pick a mix. We show the draw and the cost.The vial holds a fixed amount of drug. Adding more water does not make more drug, it just spreads it thinner, so you draw a bigger number on the syringe for the same dose.
Choose your mix
Measuring the water1 mL = one full 100-unit syringe.
Your draw
20 / 100 unitsHow do you store it?
Before mixing, and after.Dry powder in the freezer or fridge. Once mixed, fridge, and use within about a month.
Unmixed lyophilized Bimagrumab keeps for a long time cold. Once you add water the clock starts: most reconstituted vials hold up for roughly 28 to 30 days at fridge temperature. Keep it out of light, and do not freeze it after mixing.
What are the side effects and cautions?
Known cautions and warnings for this compound.Who should avoid it
- No formal contraindications established
- Pregnancy
Stop and get help
- Severe upper stomach pain, which can signal pancreas inflammation
- Signs of an allergic reaction such as face or throat swelling, hives, or trouble breathing
Common effects
- Muscle spasms, in roughly half to two thirds of people at higher doses
- Diarrhea in about four in ten
- Acne or skin eruptions
- Falls, in older trial participants
Where this page says nothing is established, that means nobody has studied it, not that a compound is safe.
Is Bimagrumab approved?
And where the numbers on this page come from.No. Not FDA-approved.
It is still being studied; a regulator has not cleared it for this use.
- DoseFrom published clinical trials. Not approved by a regulator for this dose.
- Vial sizeFrom what vendors typically list; not a recommendation.
- Reviewed22 July 2026
What else is like Bimagrumab?
Others in Muscle building, side by side.If you're weighing Bimagrumab, it's worth reading Ipamorelin + CJC-1295 blend, IGF-1 LR3, and IGF-1 DES in the same class.
An experimental shot that strips fat while adding muscle.
- Dose
- 10 up to 30 mg/kg per month (trial doses)
- How often
- Monthly
The popular growth-hormone combo in one shot, for muscle, recovery, and sleep.
- Dose
- ~100 mcg CJC + 200-300 mcg ipa
- How often
- Daily, often at night
A powerful muscle-builder that also drops blood sugar hard.
- Dose
- 0.02 up to 0.05 mg per day (start low, increase slowly)
- How often
- Daily, cycled
A short-acting muscle-builder that works right where you inject it.
- Dose
- 0.05 up to 0.15 mg per dose (start low, increase slowly)
- How often
- Around training
10What these words mean
Show glossary +
What these words mean
- Titrate
- Starting at a low dose and increasing it slowly over time so your body adjusts and side effects stay mild.
- Subcutaneous
- An injection just under the skin, into the fat layer, usually with a short, thin insulin needle.
- Intramuscular (IM)
- An injection into a muscle, using a longer needle.
- Reconstitution
- Mixing a powdered peptide with liquid (bacteriostatic water) so it can be drawn into a syringe.
- Bacteriostatic water
- Sterile water with a tiny amount of preservative, used to mix powdered peptides.
- Concentration
- How strong the mixed peptide is, in milligrams per milliliter (mg/mL). More water makes it weaker; less water makes it stronger.
- Units (on the syringe)
- The marks on an insulin syringe. 100 units equals 1 mL. They measure how much liquid you draw, not the dose in milligrams.
- mcg and mg
- Units of dose. 1 milligram (mg) equals 1,000 micrograms (mcg).
- GLP-1
- A natural gut hormone that lowers appetite and blood sugar. Drugs that copy it, like semaglutide, are used for weight loss.
- Growth hormone secretagogue
- A compound that nudges your body to release more of its own growth hormone, rather than injecting the hormone itself.
- Half-life
- How long a compound stays active in your body. A longer half-life means you inject less often.
- Peptide vs small molecule
- A peptide is a short chain of amino acids. A few items here (like MK-677 or methylene blue) are small molecules, not true peptides, but people use them the same way.
- Research only
- No approved dose or use in people. Sold for research and not reviewed by the FDA for safety or quality.
- Investigational
- Still being tested in clinical trials and not yet approved or legally sold for general use.
- Banned in drug-tested sport
- Prohibited by the World Anti-Doping Agency (WADA); using it can disqualify a competing athlete.
Last reviewed 22 July 2026