Follistatin 1 mg vial dosage

What Follistatin is

Class:

Naturally occurring single-chain glycoprotein; sold to consumers as a recombinant splice-variant fragment labelled "FST-344"

Also called:

FST, Follistatin-344, FST-344, Activin-Binding Protein

Used for:

The body's own brake on activin and myostatin signalling, studied academically as a gene-therapy payload for muscle-wasting disease. Sold separately, as an injected research-chemical protein, for grey-market muscle-building use that its own human trials have never tested.

Human evidence:

Animal / lab only. No human trial has tested the injected recombinant protein sold as a research chemical. The only human trials of therapeutically raised follistatin used a one-time viral-vector gene therapy - the vector makes muscle cells produce the FST344-encoding transgene themselves - tested in small numbers of adults with Becker muscular dystrophy and sporadic inclusion body myositis. That is a different product, a different route of administration and a single-dose intramuscular injection into diseased muscle, not a repeated systemic protein injection in a healthy person. It does not transfer as human evidence for the vial sold online, which is why this stays at preclinical rather than limited.

US status:

Research use only. Not FDA-approved for any use, and not a dietary supplement. In an April 2020 warning letter, FDA told a compounding pharmacy that Follistatin, among other bulk substances it had compounded, failed to meet the conditions for the section 503A compounding exemption - it has no applicable USP/NF monograph, is not a component of an FDA-approved drug, and does not appear on the 503A Bulks List.

The full picture, with every study: Follistatin guide.

How to mix a 1 mg Follistatin vial

For this vial: 1 mL of bacteriostatic water makes 1 mg/mL, so 300 mcg is 30 units (0.3 mL) on a U-100 insulin syringe. Pick a different volume from the units table if you want bigger or smaller draws; the number of doses stays the same.

1. Wipe the rubber stoppers of both the peptide vial and the bacteriostatic water vial with an alcohol swab and let the alcohol dry. ^[3][4]
2. With a new sterile needle and syringe, draw up the amount of bacteriostatic water you have chosen for the dilution. ^[3][4][5]
3. Inject the water into the peptide vial by aiming the stream against the inside glass wall, which helps prevent foaming. ^[6]
4. Swirl or roll the vial gently until the powder has fully dissolved; do not shake it. Do not inject the solution if it is cloudy or has particles in it. ^[3][4][6]
5. Label the vial with the date and time it was mixed, the amount of water added and how long it can be used after mixing. ^[3]
6. Store the mixed vial in the refrigerator at 2-8°C (36-46°F) and do not freeze it. ^[6]

Step by step with pictures: how to reconstitute peptides. About the water itself: bacteriostatic water.

Storing Follistatin vials

• Freeze-dried (lyophilized) peptide keeps far longer than peptide in solution; peptide suppliers advise storing the powder at -20°C away from bright light. ^[7]
• Protect peptide vials from heat and light. ^[7][8]
• Avoid repeated freeze-thaw cycles; a prescription peptide label also says not to freeze a vial once it has been mixed. ^[6][7]
• Once a multi-dose vial, such as bacteriostatic water, has been opened (needle-punctured), date it and discard it within 28 days unless its manufacturer states another date. ^[9][10]

More detail: peptide storage and shelf life.

Injecting safely

• Clean the injection site with an alcohol swab and let the skin dry completely before injecting. ^[11][12]
• Pinch up a fold of skin and fat (not muscle) and insert the needle at a 45- to 90-degree angle: 90 degrees where there is enough fatty tissue, 45 degrees where there is little. ^[11][12][13]
• Pulling back on the plunger (aspiration) is not necessary for a subcutaneous injection, because the chance of the needle being in a blood vessel is small. ^[11]
• Inject slowly, at roughly 10 seconds per mL. ^[11]
• Common sites are the belly, the thigh and the upper arm; rotate sites, keeping each injection at least 1 inch (2.5 cm) from the last. ^[6][11][12]

Hygiene and warning signs

• Use a new sterile needle and syringe for every injection and every time you enter a vial; never reuse them. ^[5][9][12]
• Never share needles, syringes or pens with anyone, even if the needle is changed; unsafe injection practices spread hepatitis B, hepatitis C and HIV. ^[5][8][9]
• Put used needles and syringes in a sharps disposal container straight away (FDA-cleared if possible), never loose in the trash, recycling or toilet, and dispose of the container following your community's guidelines. ^[14][15]
• Contact a health care provider if the injection site shows signs of infection, such as redness, swelling, red streaks or a fever. ^[12]

Where to inject: subcutaneous injection sites.

How Follistatin works

• Follistatin binds activin and myostatin (GDF-8) and stops them reaching the activin type II receptors they signal through. When mice were engineered to express follistatin at high levels in skeletal muscle, their muscle mass increased dramatically, comparable with mice that have no myostatin at all. ^[16]
• The body makes more than one form. Work on follistatin purified from pig ovaries showed that all the isoforms bind activin with about the same affinity, but the shorter FS-288 sticks to heparan sulfate proteoglycans on the cell surface while the longer FS-315 does not, so FS-288 stays attached to the cells that make it while FS-315 is released into the surrounding fluid. ^[17]
• The two human trials on this page did not inject follistatin protein at all. They used an adeno-associated viral vector carrying the FS344 splice variant, given in a single round of injections into the thigh muscles, so the patient's own muscle cells produced the protein locally. ^[18][19]

What the Follistatin research found

Human evidence: animal / lab only. Each result says what was studied.

• Animal studyMice given daily subcutaneous injections of recombinant follistatin288 for thirteen weeks had raised follistatin in serum, a dose-dependent increase in lean and muscle mass, larger muscle fibres, a shift in myosin heavy chain composition and a significant fall in body fat. ^[20]
• Animal studyIn cynomolgus macaques, a follistatin isoform delivered to the quadriceps from an AAV1 vector produced pronounced and lasting increases in muscle size and strength, and long-term expression of the transgene did not produce abnormal changes in the morphology or function of key organs. ^[21]
• Human studyIn a phase 1/2a trial, six adults with Becker muscular dystrophy received a single bilateral intramuscular quadriceps injection of AAV1.CMV.FS344, three at the lower vector dose and three at the higher. Four of the six walked further on the six-minute walk test (gains of 58, 125, 108 and 29 metres) and two did not change; biopsies showed less endomysial fibrosis and larger fibres, and the authors reported no significant adverse events related to the gene transfer. ^[18]
• Human studyIn a second trial, six adults with sporadic inclusion body myositis received the same gene therapy into both quadriceps alongside an exercise regimen. Annualised six-minute walk distance changed by +56.0 metres per year in the treated group against -25.8 metres per year in eight untreated comparators matched for age, sex and baseline (p = 0.01), with two of the six treated patients improving only 5-23 metres. ^[19]
• Human studyThat walking result was publicly contested. A 2017 letter in the same journal argued that the open-label design could not show efficacy, because the treated patients also received prednisone and an exercise programme while the comparators were clinic patients, and that the walk test was reported as the primary outcome although the registered primary outcome was safety; the trial's lead author replied in the same issue. ^[22]

Follistatin side effects and risks

No published human study has given anyone the injected recombinant follistatin protein sold online, so there is no human safety record for that product. The facts below come from the gene-therapy trials of a different intervention and from animal and cell work.

• Human studyThe Becker muscular dystrophy gene-therapy trial reports no significant adverse events related to the gene transfer across its six patients, and no abnormalities in liver, kidney, bone marrow or pituitary-gonadal hormone tests. That is a single round of viral-vector injections into diseased muscle, not repeated injections of a recombinant protein into a healthy person, and six people is far too few to detect anything uncommon. ^[18]
• Animal studyFollistatin does not act on muscle alone. Mice engineered to overexpress it developed defects in the testis, ovary and hair: several lines had much smaller testes, and in two of them spermatogenesis arrested and the seminiferous tubules degenerated, leading to infertility, while females in two lines had thin uteri, small ovaries and folliculogenesis blocked at various stages, with every female of one line infertile. ^[23]
• Lab studyThe reproductive reach is measurable at the pituitary. In cultured rat anterior pituitary cells, follistatin suppressed the release of follicle-stimulating hormone, with the cell-associated FS-288 form roughly ten times more potent than FS-315 at doing so. ^[17]

Other things to know

• FDA has already acted on this exact substance: a 2020 warning letter names Follistatin among the bulk drug substances a compounding pharmacy was told it could not lawfully use, for lacking a USP/NF monograph, FDA-approved-drug status or a place on the 503A Bulks List.
• Prohibited at all times, in and out of competition, under the WADA 2026 Prohibited List, section S4.3 (Agents Preventing Activin Receptor IIB Activation), which names follistatin by name as a myostatin-binding protein.
• Follistatin does not act on myostatin alone. It also binds activin, which has established roles in reproductive hormone regulation and other tissues well outside muscle. Broadly suppressing that signalling in a healthy person, by injection, has not been studied in humans, and any off-target effect has not been ruled out.
• No human safety or pharmacokinetic data exist for the injected protein. Vendor identity and purity claims for a vial labelled "FST-344" are not independently verified by anyone.
• No human half-life has been established, so no dosing interval has an evidence base. I do not publish one.

Reported side effects and what the studies measured: Follistatin side effects.

Where this vial size comes from

Follistatin is sold as a 1 mg vial by the pages below, each checked on the date shown. I list them as evidence that this size exists, not as a recommendation to buy from them.

• SwissChemsvendorLists it as: "Follistatin-344, 1mg" - 1 mg per vial · checked 2026-09-28
• Medica DepotvendorLists it as: "Follistatin 344 (95%) 1mg" - 1 mg Follistatin 344 per vial · checked 2026-09-28

The doses come from the sourced common protocol on the Follistatin dosing page, and every number on this page is arithmetic on those doses and this vial size.

Questions

How much water do I add to a 1 mg Follistatin vial?

There is no single correct amount: water changes how many units a dose is, not how many doses the vial holds. With 1 mL the vial is 1 mg/mL and 300 mcg is 30 units (0.3 mL) on a U-100 insulin syringe. The units table gives 1, 2, 3 mL.

How many doses are in a 1 mg Follistatin vial?

10 doses at 100 mcg, 3 doses at 300 mcg, 2 doses at 500 mcg.

How long does a 1 mg Follistatin vial last?

At 300 mcg a dose and 2 to 4 times a week, about 0.8-1.5 weeks. How long a mixed vial keeps is a separate limit; see storage below.

How many 1 mg vials do I need for a cycle?

2 vials at 100 mcg 2 times a week for 8 weeks; 32 vials at 500 mcg 4 times a week for 16 weeks.

What does 1 unit equal in a 1 mg Follistatin vial?

10 mcg with 1 mL, 5 mcg with 2 mL, 3.33 mcg with 3 mL of bacteriostatic water, on a U-100 syringe.