TRT and gym gains: separating hype from hormone science

What did @realjohnsupps actually say?

The creator claims that post-injection flu-like symptoms, sometimes called "testosterone flu," are caused primarily by the ester attached to testosterone, not the carrier oil. They ranked propionate as the worst offender, enanthate as second, and cypionate as the least likely to cause symptoms. Suspension, having no ester, was also listed as symptom-free. They also referenced "Sustanon 250" (called "Cystonon 250" in the transcript) as historically notorious for flu-like reactions, so much so that users nicknamed it "Sustanon flu."

The core argument is mechanistic: different esters release testosterone at different rates, and faster-releasing esters, like propionate, appear to trigger more pronounced immune-adjacent reactions. The creator also reassures viewers that symptoms typically resolve within a few weeks as the body adjusts, though some people continue experiencing them indefinitely with certain esters.

Does the science back this up?

Partially. The ester-rate hypothesis has biological plausibility, but the peer-reviewed evidence is thin and largely anecdotal in structure. What we do know supports some of what was said.

Testosterone esters differ in their rate of hydrolysis after injection. Propionate has a short half-life of roughly 0.8 days, enanthate around 4.5 days, and cypionate approximately 7-8 days (Behre et al., 1999, Journal of Clinical Endocrinology and Metabolism). Faster hydrolysis means a sharper initial spike in free testosterone, which could plausibly trigger a stronger systemic response. This aligns with user-reported patterns documented in forum analyses and some case series.

However, no large randomized controlled trial has directly compared flu-like symptom rates across ester types in a controlled setting. Most data comes from patient self-reports and retrospective surveys. The carrier oil, which the creator dismisses entirely, has also been implicated in post-injection reactions in case reports, particularly sesame oil sensitivity (Gittler et al., 2019, JAMA Dermatology). Dismissing the oil's role entirely is an overreach.

What did they get wrong (or right)?

They got the broad ranking directionally right, but overstated certainty and made a few specific errors worth calling out.

• Sustanon 250, not "Cystonon 250": The product they describe, notorious for multi-ester blends and flu-like reactions, is Sustanon 250. The name "Cystonon" does not correspond to any recognized pharmaceutical product. This is either a mispronunciation or a confusion, and it matters because viewers trying to research it will find nothing under that name.
• Carrier oil dismissed too quickly: The claim that flu-like symptoms have nothing to do with the carrier oil is stated as fact without evidence. Sesame oil, cottonseed oil, and grapeseed oil have different hypersensitivity profiles. Case reports document post-injection reactions tied specifically to the oil vehicle, not the hormone itself.
• The ester-rate hypothesis is reasonable: Credit where it is due. The logic that faster-releasing esters produce sharper hormonal spikes, which in turn may provoke stronger inflammatory or immune signaling, is biologically coherent. It is not proven conclusively, but it is not invented either.
• Suspension being symptom-free: This is oversimplified. Aqueous testosterone suspension carries its own injection site reaction risks and is not commonly used in TRT precisely because of tolerability issues.

What should you actually know?

Post-injection flu-like symptoms are real and documented, but their exact mechanism is still debated. If you experience them, here is what the evidence actually supports.

First, symptoms including fatigue, chills, low-grade fever, and myalgia following testosterone injection are reported by a meaningful subset of patients and are not purely psychosomatic. A 2021 survey-based study published in the Journal of Men's Health found that injection site and systemic reactions were among the most common reasons patients switched ester formulations.

Second, if symptoms are severe or persistent beyond four to six weeks, that warrants a clinical conversation, not just a switch to a different ester based on a TikTok recommendation. Persistent systemic symptoms after injection could reflect oil sensitivity, infection at the injection site, or a reaction to excipients in compounded formulations.

Third, the creator's suggestion to switch esters is not inherently bad advice, but it should happen under the supervision of a prescribing clinician, not as a self-directed experiment. Compounded formulations vary in carrier oil, concentration, and purity, and those variables matter.