Thymalin
Thymalinum · Thymus peptide complex
Thymalin is not one molecule. It is a complex of polypeptides extracted from calf thymus, and that distinguishes it from almost everything else on this site in a way that matters more than any dosing detail: two vials from different producers, or from the same producer in different years, are not necessarily the same substance.
It was developed in the Soviet Union in the 1970s and is registered as a medicine in Russia and several neighbouring states, where it has been used in immune-related indications for decades. There is a substantial Russian literature around it, including reports from long-running studies in elderly populations that describe reduced mortality.
Those reports are the interesting and difficult part. They are real publications describing real work, and they are also hard to evaluate against contemporary standards. Trial registration, protocol pre-specification, blinding and independent replication are largely absent, most of the work is published in Russian in journals with limited international review, and no Western group has replicated any of it. That is not a claim the findings are wrong. It is a statement that the usual machinery for checking them has not been applied, and forty years on it still has not.
How it works
Thymalin is understood to act on T-lymphocyte maturation, mirroring what the thymus does naturally. The thymus atrophies steadily from adolescence onward, and the decline in T-cell diversity that follows is one of the better-documented features of an ageing immune system. Supplying thymic peptides to counter that is a coherent idea.
Because thymalin is a mixture, not a defined molecule, its mechanism cannot be described the way a single peptide's can. Which components are active, and in what proportion, is not established. That is exactly the question a defined synthetic peptide like thymosin alpha-1 was created to answer.
The longevity claims attached to it rest on the argument that restoring immune competence in the elderly reduces death from infection and cancer. That chain of reasoning is plausible at every link and has not been demonstrated end to end in a modern trial.
Regulatory status — Russia and United States
Registered as a medicine in Russia and several neighbouring states for immune-related indications. Not approved in the United States, the European Union or the United Kingdom, where it is sold only as a research chemical. Because it is an extract rather than a synthesised peptide, purity and composition vary between producers in a way they do not for defined peptides.
Last reviewed 16 Aug 2026. Regulatory positions in this category change frequently; we date this line so you can see how current it is.
What it is studied for
Each entry states the evidence behind it. We do not rank indications by effectiveness — for most compounds here, that would be a claim nobody can support.
Immune support in illness and recovery
Published reviewThe registered use in Russia.
EvidenceRegistered as a medicine in Russia on the basis of Soviet-era and Russian clinical work. That work has not been replicated to contemporary standards elsewhere.
Reducing mortality in elderly populations
Published reviewThe claim that draws people to it.
EvidenceLong-running Russian follow-up studies report reduced mortality in elderly cohorts. Not registered trials — not blinded to contemporary standards — and never independently replicated.
Identity and clearance
Molecule
- Class
- Polypeptide fraction extracted from calf thymus; not a single defined molecule
No molecular weight or sequence can be given, because the product is a mixture whose composition varies by producer and batch. This is the central fact about it.
Dose protocols reported in sources
Displayed for reference only. Every row says where it came from, and a trial protocol and a community convention are not the same kind of information. None of this is fed into the calculator, and none of it is a recommendation.
| Goal | Dose | Frequency | Route | Units, 10 mg vial | Source | Start this protocol |
|---|---|---|---|---|---|---|
| Course described in the Russian clinical literature | 5 mg – 10 mg | Daily for 5 to 10 days, as a course rather than continuously | IntramuscularGiven intramuscularly in the Russian protocols, as short courses repeated periodically rather than as ongoing therapy. Note that the milligram figures refer to the extract by weight, not to a quantity of any defined active peptide. Dose comparisons between producers are therefore not meaningful. | 50–100 u | Published review | Start this |
Start this copies a row into a protocol of your own, which you can then edit. Where a source gave a dose range or an ambiguous frequency, those fields arrive empty — we will not pick a number on your behalf.
Cycling
Published review5 to 10 days on, Months, with courses repeated once or twice a year off.
The course-based pattern comes from the Russian clinical protocols rather than from community convention, which makes it better grounded than most cycling schedules on this site, though the underlying evidence carries all the same limitations.
Calculator
Work out what to draw
Pre-filled with a 10 mg vial as a worked example. These are not recommended values — change them to match the vial in front of you.
Draw to 50 units on a 1 mL U-100 syringe. That is 0.5 mL, containing 5 mg of Thymalin.
50 units sits exactly on a printed line.
Bioalmanac performs arithmetic on values you enter. It does not recommend doses, schedules or compounds, and nothing here is medical advice. Confirm every calculation against your vial and syringe before drawing, and speak with a licensed healthcare provider.
Open this calculation in the full calculator
Units, concentration, bacteriostatic water — the glossary defines the vocabulary, and a unit is not a fixed volume.
Safety
Reported effects
- Injection site pain and irritationCommunity practice
Commonly reported
Intramuscular administration of an extract is more irritating than a subcutaneous synthetic peptide.
- Allergic reaction to animal-derived materialPublished review
Uncommon, but the distinctive risk here
This is a bovine tissue extract. Allergic and immune reactions to animal-derived protein are a category of risk that does not apply to synthesised peptides at all.
- Effects of an immune-active agent in autoimmune diseasePublished review
Unknown
A compound intended to stimulate immune function has an obvious and unstudied interaction with conditions caused by an overactive immune system.
- Batch-to-batch variation in what you are actually takingPublished review
Inherent to an extract
Not a side effect in the usual sense, and more consequential than most of them. There is no assay a buyer can run that would establish equivalence between two producers' vials.
When to stop
- Any allergic response: rash, hives, facial swelling or difficulty breathing. Seek urgent care — the animal-derived origin makes this more relevant here than for synthetic peptides.
- A flare of any existing autoimmune condition.
- Fever, or an injection site that becomes hot, spreading or produces pus.
- Swollen lymph nodes that persist.
Interactions and situations that need care
- Autoimmune diseaseAvoid
The compound's purpose is to stimulate immune function, and autoimmune disease is immune function attacking the body. Nothing establishes what thymalin does in that setting, and the mechanism points the wrong way.
- Immunosuppressant therapy, including after transplantAvoid
Deliberately stimulating T-cell function in someone whose treatment depends on suppressing it risks organ rejection or loss of disease control.
- Known allergy to bovine proteinAvoid
This is a calf thymus extract, and residual animal protein is intrinsic to what it is, not a contaminant that better manufacturing would remove.
- Pregnancy and breastfeedingAvoid
No reproductive or developmental safety data.
- Expecting consistency between vialsUse caution
An extract is not a defined molecule. Two producers' products may differ in composition, and no certificate of analysis a buyer can obtain will establish that they match. If you value knowing what is in the vial, thymosin alpha-1 is a defined synthetic peptide with a comparable rationale.
What to expect
HonestlyThere is no human efficacy data for this compound, so there is no evidence-based timeline to give. Any site publishing a week-by-week schedule of expected effects has invented it.
- It is a mixture, not a molecule. That single fact undermines dose comparisons, purity testing and any expectation that one vial matches another.
- The Russian clinical literature is real, and it is not evaluable to contemporary standards: unregistered, largely unblinded, published in limited-review venues, and never independently replicated in forty years.
- The mortality claims come from long follow-up studies of that kind. Treat them as an interesting unreplicated finding, not an established result.
- If the thymic mechanism is what interests you, thymosin alpha-1 is a defined synthetic peptide with the same rationale and a body of registered clinical work behind it.
- The animal-derived origin introduces an allergy risk that does not exist for synthesised peptides.
Storage and handling
- Freeze-dried powder
- Refrigerated at 2–8 °C, protected from light.
- After mixing
- Refrigerated at 2–8 °C, and used within days rather than weeks. Biological extracts are less predictable in solution than synthetic peptides.
- Long-term, frozen
- Unopened powder is stable at −20 °C or colder.
With other peptides
- Thymosin alpha-1caution
Thymosin alpha-1 is a defined synthetic peptide originally identified in thymic extract, and most likely one of the components of thymalin itself. Running both is probably taking the same thing twice, once in a known quantity and once in an unknown one.
- Thymulincaution
Thymalin plausibly contains thymulin among other things, being an undefined extract of the same gland. Taking both is likely taking the same class of thing twice.
Checking your vial
Research chemicals carry no manufacturing standard, so what the vial looks like is often the only quality signal available before you use it. More on assessing quality and COAs.
White to off-white cake, clear solution
A slight off-white tint is more common in extracts than in synthetic peptides and is not itself a fault.
Any visible variation between vials of the same batch
Extracts vary more than synthesised peptides. Visible inconsistency within a single batch suggests poor process control.
Cloudy solution or visible particles after gentle mixing
Do not use it.
Questions
- Is thymalin a peptide?
- Not a peptide, singular. It is a mixture of polypeptides extracted from calf thymus, and the composition is not fully defined. That is the most important thing to know about it.
- How seriously should I take the Russian longevity studies?
- Seriously enough to read about, not seriously enough to treat as established. They report reduced mortality in elderly cohorts over long follow-up. They were not registered trials, were not blinded to contemporary standards, are published mostly in Russian in venues with limited international review, and no independent group has replicated them in four decades.
- How is it different from thymosin alpha-1?
- Thymosin alpha-1 is a single 28-amino-acid peptide, synthesised, with a defined structure and registered clinical use in several countries. Thymalin is an undefined extract. If you want the thymic mechanism with something you can actually verify, thymosin alpha-1 is the one to look at.
References
Thymalin in clinical use: the Russian and Soviet-era literature on thymic peptide preparations
Russian clinical and immunological literature, 2003 · Body of clinical reports, largely unregistered and not blinded to contemporary standards
Humans
Reports immune-modulating effects supporting registration as a medicine in Russia. Methodology, reporting and the absence of independent replication limit how much weight these findings can carry outside that context.
Long-term follow-up of thymic peptide administration in elderly cohorts
Russian gerontology literature, 2003 · Long-term follow-up studies, not randomised or blinded to contemporary standards
Elderly humans
Reports reduced mortality over extended follow-up in treated cohorts. The design cannot separate the intervention from differences between groups, and no independent replication exists.
Related compounds
Thymosin alpha-1
An immune-modulating peptide approved in more than thirty countries for hepatitis B, and studied in sepsis and as a vaccine adjuvant. Not approved in the United States.
Thymulin
A genuine thymic hormone with real immunology behind it, and no clinical development. It only works with zinc bound to it, which is the most useful fact about it.
GHK-Cu
A naturally occurring copper-binding tripeptide with a long history in topical skincare research. Injected use is not what the research studied.
Ipamorelin
A selective growth hormone secretagogue that prompts a short pulse of GH release. Widely used, and supported almost entirely by early pharmacology rather than outcome trials.
Next
What to do with Thymalin
- Keep a record of itTurn a dose and a schedule into a protocol, then log what you actually take. Thymalin is filled in for you.
- See what it costsPer-milligram prices read from vendor sites and confirmed by a person, so vial sizes compare.
- Check a combinationWhat our profiles record about Thymalin alongside each other compound — including the pairs where nothing is recorded.
Keep this page honest
If something here is wrong, out of date, or missing a source, tell us and we will fix it and say that we did.
This page is educational. It describes what published research reports, not what you should do. Peptides discussed here are largely not approved for human use, and nothing on Bioalmanac is medical advice. No clinician reviews these pages.
Page last updated 16 Aug 2026