Will it make me infertile?

It stops sperm production in most men while taken. That is often reversible after stopping, and less reliably so the longer it has been going on. hCG alongside it substantially reduces the problem. If children are a possibility, bank sperm before starting. It is straightforward beforehand and not an option once suppression is established.

Can I stop once I start?

You can, and your own production will be suppressed when you do. Recovery typically takes months and is not guaranteed after years of use. This is why the diagnosis matters so much more than it seems at the point of starting.

Is it bad for the heart?

The TRAVERSE trial found testosterone non-inferior to placebo for major adverse cardiac events in men with hypogonadism and cardiovascular risk, which was reassuring. The same trial found higher rates of atrial fibrillation, pulmonary embolism and acute kidney injury. Anyone citing only one of those results is selling something.

Why is a steroid on a peptide site?

Because people track it alongside peptides, and because leaving it out would mean the fertility consequence goes unstated in the one place someone might read it before starting.

Muscle & performance

Testosterone (TRT)

TRT · Testosterone replacement therapy · Testosterone cypionate · Testosterone enanthate

ApprovedProhibited in sportReviewed 18 Aug 2026

Testosterone is a steroid hormone, not a peptide. It is on this site because people track it alongside everything else here, and because the most important fact about it, that it suppresses your own production and your fertility, is the one most likely to be discovered too late.

As replacement therapy for diagnosed hypogonadism it is well-evidenced approved medicine, and for men who genuinely have low testosterone confirmed on repeat morning bloodwork, it works: energy, mood, libido, bone density, body composition. That is a real treatment for a real diagnosis.

The gap between that and how it is actually obtained is wide. Online clinics prescribe from a single blood draw and a symptom questionnaire, when diagnosis requires at least two morning measurements plus an assessment of why levels are low. Symptoms of low testosterone are also the symptoms of poor sleep, obesity, depression and thyroid disease, and some of those are reversible in a way that starting lifelong therapy is not.

Two things are worth knowing before starting. It suppresses your own production, and after prolonged use recovery is uncertain and can take a year or more. And it stops sperm production in most men, which is reversible for many and not for all. Neither is a side effect at the margin; both are what the drug does.

How it works

Testosterone binds the androgen receptor, driving protein synthesis, red blood cell production, bone density and the range of effects associated with male physiology.

Some converts to oestradiol via aromatase, and that matters. Oestradiol in men is necessary for bone and libido, and both too little and too much cause problems. This is why aromatase inhibitors are commonly over-used alongside it.

Some converts to dihydrotestosterone via 5-alpha reductase, which drives prostate and scalp effects.

Exogenous testosterone suppresses GnRH, LH and FSH through negative feedback. Without LH the testes stop producing their own; without FSH sperm production stops. This is the mechanism behind both testicular atrophy and infertility, and it is not avoidable by dosing carefully.

Quick reference

Commonly described dose: 50 mg–100 mg
How often: Weekly, or split twice weekly
Route: Intramuscular or Subcutaneous or Topical
Where: Thigh, Gluteal, Abdomen
Timing: Weekly or twice weekly for injectables; daily for gels. Bloodwork is drawn at trough, immediately before the next dose.
Storage once mixed: Refrigerated, 90 days

These describe what sources report, not what you should do. Full detail and provenance in the dosing section below.

Price index

Per-milligram pricing across vendors arrives with the directory. We are recording prices now so the history exists when the page ships.

Vocabulary on this page

Adherence: Whether doses were actually taken as planned. The gap between a schedule and a record.
Intramuscular: Into muscle rather than the fat beneath the skin. A faster and better-perfused route, needing a longer needle.
Reconstitution: Adding liquid to a freeze-dried peptide powder to turn it into a solution that can be drawn into a syringe.
Vial: The small sealed glass container a peptide is sold in, holding a stated mass of freeze-dried powder under a rubber stopper.
Evidence level: The category of human evidence behind a compound, from preclinical through to approved. Stated on every profile here as a category, not an adjective.
Peptide: A short chain of amino acids: the same building blocks as a protein, in a chain short enough to behave differently.

The whole glossary →

Regulatory status — United States

Approved by the FDA and EMA for diagnosed male hypogonadism, and a Schedule III controlled substance in the United States. Labelling was updated in 2025 following the TRAVERSE trial. Not approved for age-related decline in testosterone without a confirmed diagnosis.

Last reviewed 18 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.

Diagnosed male hypogonadism

Published review

The approved indication.

EvidenceExtensive trial evidence for improvements in sexual function, mood, bone density and body composition in men with confirmed low testosterone.

Cardiovascular safety

Clinical trial

A long-standing question, now largely answered.

EvidenceThe TRAVERSE trial, in men with hypogonadism and cardiovascular risk, found testosterone therapy non-inferior to placebo for major adverse cardiac events. It also found higher rates of atrial fibrillation, pulmonary embolism and acute kidney injury.

Performance and body composition in men with normal levels

Clinical trial

Not an approved use.

EvidenceSupraphysiological testosterone increases muscle mass and strength. That is not in doubt. It is also not replacement therapy, and the risk profile is different.

Identity and clearance

Molecule

Class: Steroid hormone, not a peptide
Molecular weight: 288.4 Da

Included here because it is tracked alongside peptides, not because it belongs to the same class.

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.

Dose protocols reported in sources, with the source of each.
Goal	Dose	Frequency	Route	Units	Source	Start this protocol
Replacement therapy, injectable ester	50 mg – 100 mg	Weekly, or split twice weekly	Intramuscular50 to 100 mg per week is the usual replacement range for cypionate or enanthate, titrated against trough total testosterone, haematocrit and oestradiol. Splitting the dose gives steadier levels. The figures here are in micrograms for consistency with the rest of the site; every clinical source uses milligrams.	—	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.

Safety

Reported effects

Suppression of your own productionPublished review
Universal
Not a side effect so much as the mechanism. Recovery after prolonged use is uncertain and can take a year or longer.
InfertilityPublished review
Most men, while taking it
FSH suppression stops sperm production. Often reversible, not always, and less so the longer it has been going on. If you may want children, discuss this before starting rather than after.
Raised haematocritPublished review
Common
Thickened blood raises clot risk. This is the single most important thing routine bloodwork is looking for, and it is manageable when someone is checking.
Testicular atrophyPublished review
Common
Acne and oily skinPublished review
Common
GynaecomastiaPublished review
Common
From aromatisation to oestradiol. Managed by dose adjustment, and over-suppressing oestradiol with an aromatase inhibitor causes its own problems: joint pain, low libido, bone loss.
Atrial fibrillation, pulmonary embolism and acute kidney injuryClinical trial
Higher than placebo in TRAVERSE
The same trial that established cardiovascular non-inferiority found these raised. Both findings belong together.
Worsening sleep apnoeaPublished review
Reported
Mood changes and irritabilityPublished review
Reported

When to stop

Chest pain, breathlessness, or leg pain and swelling. Clot symptoms. Seek emergency care.
Haematocrit above the range your clinician set. This needs a dose change or a blood donation, not waiting.
Breast tenderness or enlargement.
Severe mood changes, aggression or worsening depression.
Worsening snoring or daytime sleepiness. Sleep apnoea.
Reduced urine flow or difficulty passing urine.

Interactions and situations that need care

Prostate or breast cancerAvoid
Testosterone drives growth in hormone-sensitive tissue. An absolute contraindication in the prescribing information.
Wanting to conceive, now or laterAvoid
It stops sperm production in most men. Recovery is common but not guaranteed, and becomes less likely with longer use. Sperm banking before starting is the standard advice and is easy to arrange beforehand and impossible afterwards.
Untreated severe sleep apnoeaAvoid
Testosterone can worsen it, and severe untreated apnoea carries its own cardiovascular risk.
Raised haematocrit or polycythaemiaAvoid
It raises red cell mass further. This is the most common reason therapy is paused, and it needs monitoring rather than judgement.
Women, and anyone who is pregnantAvoid
Causes virilisation, and is harmful to a developing fetus. Note that gels transfer by skin contact, which has caused virilisation in partners and children.
Starting without repeat morning bloodwork and a diagnosisAvoid
Diagnosis needs at least two morning measurements and an assessment of why levels are low, because the symptoms overlap almost entirely with poor sleep, obesity, depression and thyroid disease. Some of those are reversible. Starting testosterone is close to permanent. It suppresses what it replaces, so stopping means recovering over many months, or not fully recovering. A clinic that prescribes from one draw and a questionnaire has skipped the part that decides whether this is the right treatment.
Competing in a tested sportAvoid
WADA class S1, prohibited at all times, and testing for it is routine and long established.

SportProhibited by the World Anti-Doping Agency under S1: Anabolic Agents, at all times, in and out of competition. Testing for exogenous testosterone is long established and routine, including isotope-ratio methods that distinguish it from what the body makes.

What to expect

For diagnosed hypogonadism this works and is well evidenced. That is not the same as it being right for low-normal levels and tiredness.
It stops sperm production in most men. Bank sperm before starting if children are a possibility.
It suppresses your own production. Coming off after years means an uncertain recovery measured in months.
TRAVERSE settled the cardiovascular question in the reassuring direction, and found raised atrial fibrillation, pulmonary embolism and kidney injury. Both halves are the result.
Haematocrit is the number that most often forces a change. Without bloodwork you will not know it has risen.
It is not a peptide. It is on this site because people track it here, and because the fertility consequence is the one most often learned too late.

Storage and handling

Freeze-dried powder: Supplied as an oil solution, not a powder. Store at room temperature, away from light.
After mixing: Nothing to reconstitute. A multi-dose vial is good until its expiry if the stopper is cleaned before each draw.
Long-term, frozen: Do not refrigerate or freeze. The oil thickens and crystals form.

Printable one-pager How to reconstitute a vial, step by step

With other peptides

HCGsynergistic
The standard pairing. hCG replaces the pituitary signal that testosterone suppresses, maintaining testicular size and sperm production. Normally prescribed together rather than added independently.
Gonadorelinsynergistic
Used for the same purpose as hCG, acting on the pituitary instead of the testes. Which one suits depends on where the suppression sits, which is a clinical question.
MK-677caution
Both cause fluid retention, and MK-677 also worsens insulin sensitivity. The combination compounds oedema and metabolic effects.

Check this against a whole stack

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.

Clear oil solution, faintly yellow
Normal. Cypionate and enanthate are dissolved in cottonseed or sesame oil.
Visible crystals
Usually from being stored cold. Warming the vial in the hand normally redissolves them.
No manufacturer packaging, lot number or expiry
Underground-lab testosterone is common and inconsistently dosed. There is no way to assess it by eye.

Questions

Will it make me infertile?: It stops sperm production in most men while taken. That is often reversible after stopping, and less reliably so the longer it has been going on. hCG alongside it substantially reduces the problem. If children are a possibility, bank sperm before starting. It is straightforward beforehand and not an option once suppression is established.
Can I stop once I start?: You can, and your own production will be suppressed when you do. Recovery typically takes months and is not guaranteed after years of use. This is why the diagnosis matters so much more than it seems at the point of starting.
Is it bad for the heart?: The TRAVERSE trial found testosterone non-inferior to placebo for major adverse cardiac events in men with hypogonadism and cardiovascular risk, which was reassuring. The same trial found higher rates of atrial fibrillation, pulmonary embolism and acute kidney injury. Anyone citing only one of those results is selling something.
Why is a steroid on a peptide site?: Because people track it alongside peptides, and because leaving it out would mean the fertility consequence goes unstated in the one place someone might read it before starting.

References

Testosterone cypionate and enanthate: FDA prescribing information
US Food and Drug Administration, 2025 · Regulatory label
Men with diagnosed hypogonadism · Titrated against trough total testosterone
Approved for diagnosed male hypogonadism. Contraindicated in prostate or breast cancer. Warnings cover polycythaemia, sleep apnoea, suppression of spermatogenesis, and secondary exposure from topical formulations. Schedule III in the United States. Labelling was revised in 2025 following the TRAVERSE results.
Cardiovascular safety of testosterone-replacement therapy (TRAVERSE)
New England Journal of Medicine, 2023 · Randomised, double-blind, placebo-controlled non-inferiority trial
5,246 men aged 45 to 80 with hypogonadism and cardiovascular disease or high risk · Transdermal testosterone gel, titrated
Testosterone was non-inferior to placebo for major adverse cardiac events. Higher incidences of atrial fibrillation, acute kidney injury and pulmonary embolism were observed in the testosterone group.
10.1056/NEJMoa2215025
Community and clinic practice, unverified
Forums, coaching protocols and wellness-clinic marketing, 2026 · Anecdote
Self-selected, unverified
Doses and schedules described outside medical supervision. No study design — no adverse event capture — and heavy selection bias.

Related compounds

HCG

An approved fertility medicine that mimics LH. Widely used to keep the testes working during testosterone therapy. Also sold, separately, for a weight-loss diet the FDA has said outright does not work.

Gonadorelin

Natural GnRH, approved as a diagnostic agent. Widely used alongside testosterone therapy on a rationale that is sound in principle and unstudied in that setting.

MK-677

An orally active ghrelin receptor agonist that raises growth hormone and IGF-1. Not a peptide, and not injected. It is a small molecule taken by mouth.

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.

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.

Suggest a correction

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 18 Aug 2026