Every completed human trial of SS-31 has used the same figure: 40 mg once daily, injected under the skin. That number is the only firm anchor in any conversation about SS-31 peptide dosage, and it comes with conditions attached — it was fixed inside a clinical protocol, in named diseases, with monitoring, using a manufactured drug. Outside a protocol there is no established dose for compounded SS-31, and no chart on a seller's page supplies one.
SS-31 and elamipretide are two names for the same peptide; what the molecule is and how it binds cardiolipin is covered separately. This page is about the numbers.
Where the SS-31 peptide dosage figures come from
Human dosing of this peptide was set by a drug-development program that began with an intravenous dose-escalation and then moved to a single fixed daily injection.
The first controlled human study, MMPOWER, gave elamipretide intravenously by body weight — 0.01, 0.1 and 0.25 mg/kg per hour over two hours, in an escalating sequence, to 36 adults with primary mitochondrial myopathy. Participants on the highest rate walked a mean 64.5 m further at day 5 against 20.4 m on placebo (p = 0.053), and distance walked rose with dose across the range (p = 0.014) (Karaa et al., Neurology 2018). Every trial since has used 40 mg a day subcutaneously.
| Trial | Population | N | Dose administered | Duration |
|---|---|---|---|---|
| MMPOWER (2018) | Primary mitochondrial myopathy | 36 | 0.01 / 0.1 / 0.25 mg/kg/h intravenous over 2 h | 5 days |
| MMPOWER-2 (2020) | Primary mitochondrial myopathy | 30 | 40 mg/day subcutaneous | 4 weeks per arm, crossover |
| MMPOWER-3 (2023) | Primary mitochondrial myopathy | 218 | 40 mg/day subcutaneous | 24 weeks |
| TAZPOWER (2021) | Barth syndrome | 12 | 40 mg/day subcutaneous | 12 weeks per arm, crossover |
| ReCLAIM (2022) | Dry AMD with noncentral geographic atrophy | 19 | 40 mg/day subcutaneous | 24 weeks |
| ReCLAIM-2 (2025) | Dry AMD with geographic atrophy | 176 | 40 mg/day subcutaneous | 48 weeks |
| PROGRESS-HF (2020) | Heart failure with reduced ejection fraction | 71 | 4 mg or 40 mg/day subcutaneous | 28 days |
Two things stand out. The dose did not vary with the condition — mitochondrial myopathy, Barth syndrome, dry age-related macular degeneration and heart failure were all studied at 40 mg a day — and it stopped being weight-based after that first study, every later trial using a fixed milligram amount rather than a mg/kg calculation.
PROGRESS-HF is the only later trial that compared two subcutaneous doses head to head, randomizing 71 people with reduced ejection fraction to placebo, 4 mg or 40 mg daily for 28 days; the imaging primary endpoint was not met at either dose (Butler et al., J Card Fail 2020). Several of these trials missed their primary endpoints. MMPOWER-3 ran 218 people for 24 weeks at 40 mg a day and produced a six-minute-walk difference of −3.2 m against placebo (p = 0.69) (Karaa et al., Neurology 2023). A dose that has been studied is not the same thing as a dose that has been shown to work.
The one labeled elamipretide dose, and what it covers
In September 2025 the FDA granted accelerated approval to elamipretide, marketed as Forzinity by Stealth BioTherapeutics — the first disease-specific treatment for Barth syndrome (Shirley, Drugs 2026). That product carries a complete dosing scheme, which is worth reading precisely because of how narrow it is.
The label covers improving muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg, at 40 mg subcutaneously once daily. The dose is halved to 20 mg once daily in severe renal impairment — an eGFR below 30 mL/min in people not on dialysis — and left unchanged in mild or moderate impairment. It is supplied as 280 mg in 3.5 mL, a concentration of 80 mg/mL, in single-patient vials; injections go into the abdomen or outer thigh with the site rotated daily, and a missed dose is skipped rather than doubled (FORZINITY prescribing information, DailyMed).
Notice what that scheme is bounded by: one manufactured product, one ultra-rare genetic disease, one weight band, one route. It is not a general-purpose dosing table for a peptide, and it was never written as one.
SS-31 prescribed through a telehealth service is prepared as a compounded medication, which is different from an FDA-approved product: the compounded formulation offered here is not FDA-approved. A licensed provider may still prescribe it where they judge it appropriate — that decision is between you and your doctor.
SS-31 and MOTS-c are not interchangeable numbers
SS-31 and MOTS-c are both peptides studied for their activity at the mitochondrion, which is why they are so often discussed in the same breath. Their dose figures come from entirely separate literatures, and neither transfers to the other — MOTS-c dosing is its own question with its own evidence.
Why a seller's dosing chart is not a protocol
Vials sold without a prescription usually arrive with a chart: a milligram range, a frequency, sometimes a cycle of so many weeks on and so many off. Those numbers look like the trial numbers and are not doing the same job.
- A dose without a denominator is not information. In a trial, 40 mg a day is attached to a named population, a fixed duration, a monitoring schedule and an endpoint that either moved or did not. Lift the figure out and all four disappear.
- The vial is not the dose. SS-31 is supplied as a powder that has to be reconstituted, and the volume of diluent decides how many milligrams sit in each syringe unit. Two people following the same chart with different reconstitution volumes are taking different amounts — how reconstitution works covers that arithmetic.
- Nobody is adjusting it. The approved label halves the daily dose in severe renal impairment. A chart cannot know your kidney function, your other medicines, or that the injections stopped being tolerable in week three.
What a prescriber weighs
For a compounded peptide with no established dose, the decision is mostly about whether to prescribe at all, and then about keeping the exposure conservative and observable. What tends to come up:
- Whether there is a coherent clinical reason. The human evidence sits in specific diagnoses — mitochondrial myopathy, Barth syndrome, dry AMD, heart failure — mostly with disappointing primary results. A request that resembles none of them is a harder case to make.
- Kidney function, since that is the one variable the labeled dosing scheme adjusts for.
- Other medicines and conditions, plus pregnancy or breastfeeding, which rules out essentially everything in this category.
- Injection tolerability. Injection-site reactions were the dominant adverse event at 40 mg a day in every trial: 80% of the 30 participants in the MMPOWER-2 crossover, mostly mild (Karaa et al., J Cachexia Sarcopenia Muscle 2020), and 86% of people on elamipretide versus 71% on placebo for adverse events overall in the 176-person ReCLAIM-2 trial (Ehlers et al., Ophthalmol Sci 2025). In a 19-person phase 1 study, one participant withdrew because of an intolerable injection-site reaction (Mettu et al., Ophthalmol Sci 2022).
- How long, and what would count as an answer. Published durations ran from 5 days to 48 weeks; the Barth syndrome crossover used 12-week arms (Reid Thompson et al., Genet Med 2021). An open-ended prescription with no review date is not a plan.
What to settle before the first injection
The useful conversation is not "how many milligrams". It is which problem you are hoping to affect, what a daily injection actually commits you to, what would tell you it is not working, and when you will next be reviewed. Those questions have answers. A number lifted off a chart only looks like one.
SS-31 is available only by prescription. A licensed provider reviews every request and prescribes only where it is appropriate; not everyone qualifies, and a provider may decline. If you have not been through that before, how peptides get prescribed walks through the steps.