Restore Your Testosterone. Energy. Strength. Vitality.
Doctor-prescribed testosterone support delivered discreetly to your door.
Physicians
Private
Delivery
Sermorelin Acetate
Peptide therapy to support natural hormone production.
- Supports Natural HGH
- Boosts Energy & Recovery
- Physician-Prescribed
Enclomiphene Flex-Dose
Raises natural testosterone without shutting down production.
- Boosts Natural Testosterone
- Preserves Fertility
- Flexible Daily Dosing
DHEA Testosterone Support
Foundational hormone support for energy and drive.
- Supports Healthy Hormones
- Improves Energy & Mood
- Once-Daily Capsule
Testosterone injections are one of the most common ways men in the US treat clinically low testosterone, and for most patients they work reliably and predictably. But "works well" doesn’t mean "side-effect free." Even when your levels are dialed in to a textbook range, your body is reacting to a hormone shift that touches blood, mood, skin, fertility, and prostate tissue.
If your prescriber just handed you a script for testosterone cypionate or enanthate, you’re probably wondering what’s normal, what’s worth a phone call, and what means stop and get bloodwork now.
That’s the honest map below. Seven side effects worth tracking, why they happen, and what the FDA labeling for testosterone products actually warns about.
Why Testosterone Injections Cause Side Effects in the First Place
Injected testosterone doesn’t just refill a low tank. It produces peaks and troughs that the body never sees from natural production, and some of that extra hormone gets converted into estradiol and dihydrotestosterone (DHT). Most side effects trace back to one of those three things: the testosterone itself, the estrogen rise, or the DHT rise.
What I tell patients is this: bloodwork at 6 weeks, 6 months, and yearly isn’t optional. It’s the only way to catch the issues below before they become real problems. The Endocrine Society’s clinical guideline on testosterone therapy is pretty clear on that monitoring schedule.
1. Elevated Red Blood Cell Count (Erythrocytosis)
This is the side effect that surprises people most. Testosterone injections stimulate the bone marrow to produce more red blood cells, and in a meaningful subset of men, the hematocrit climbs above 54%, which is the cutoff most clinicians use to pause therapy.
Why it matters: thicker blood raises stroke and clot risk. It’s also more common with injections than with gels, because of those peak-and-trough swings.
What to watch for:
- Headaches that feel different than your usual
- Flushed, ruddy face
- Dizziness or vision changes
- Tingling in hands or feet
The fix is usually a dose reduction, a switch to weekly or twice-weekly dosing instead of every-two-weeks, or therapeutic phlebotomy (donating blood).
2. Acne and Oily Skin
DHT ramps up sebum production. For men who breezed through their teens with clear skin, suddenly breaking out on the back and shoulders in their 40s is jarring. It’s not dangerous, but it’s the most common cosmetic complaint with testosterone injections.
Mild cases respond to a benzoyl peroxide wash. More stubborn cases sometimes need a prescription retinoid, and our breakdown of tretinoin vs adapalene for acne covers which one usually fits which skin type.
3. Mood Swings and Irritability
The peak-trough cycle of testosterone injections can drag mood along with it. Patients often describe the first 2 to 4 days post-injection as feeling sharp and motivated, and the last few days before the next shot as flat, irritable, or anxious.
More frequent, smaller doses (twice weekly, for example) tend to smooth this out. If mood swings are severe or include depression, that’s a same-week call to your prescriber, not a "wait for the next appointment" issue.
4. Testicular Shrinkage and Reduced Fertility
When you inject exogenous testosterone, your brain gets the signal that levels are high and shuts down your own production. Luteinizing hormone drops, the testes stop making testosterone, and sperm production drops with it. Most men on testosterone injections become functionally infertile within months.
For men who want to preserve fertility, this is the single biggest reason to consider an alternative. Our comparison of clomiphene vs testosterone for low T walks through why clomiphene is often a better fit for younger men still planning families.
Testicular volume usually shrinks noticeably within 3 to 6 months. It typically recovers after stopping therapy, though not always fully.
5. Gynecomastia (Breast Tissue Growth)
Some of the testosterone you inject aromatizes into estradiol. When estradiol climbs disproportionately, breast tissue can grow, and it’s often tender before it’s visible. This isn’t water weight or fat. It’s actual glandular tissue, and once it’s established, it usually requires surgery to remove.
Catch it early. If your nipples feel sore or you notice a firm disc of tissue under the areola, get an estradiol level checked. Dose adjustment or, in some cases, an aromatase inhibitor can stop progression.
6. Prostate Changes and Urinary Symptoms
Testosterone doesn’t cause prostate cancer, despite decades of confusion on that point. But it can accelerate growth of existing prostate tissue, which means men with benign prostatic hyperplasia (BPH) may notice worsening urinary symptoms, weaker stream, more nighttime trips to the bathroom, harder to start.
The NIH overview of testosterone therapy risks lays out the current evidence here. Baseline PSA before starting, repeat at 6 months, then annually. If you’re already managing BPH, our piece on tamsulosin vs alfuzosin for BPH is worth a read before you start testosterone injections, because your prescriber may want both treatments coordinated.
7. Injection Site Reactions
The forgotten side effect. Intramuscular testosterone is suspended in oil (cottonseed or sesame, depending on the formulation), and that oil can cause local pain, redness, swelling, or a sterile abscess at the injection site. Some men also have allergic reactions to the carrier oil itself.
Rotating injection sites, using the right needle length, and warming the vial in your hand before drawing up usually handles the routine soreness. Persistent redness, fever, or a hard lump that doesn’t go away in a week needs medical attention.
For cost comparison and pharmacy options, you can check pricing on testosterone cypionate at edrugstore.com before your next refill.
When to Call Your Prescriber Right Away
Some side effects of testosterone injections can wait for your next visit. These can’t:
- Chest pain, shortness of breath, or leg swelling (possible clot)
- Sudden severe headache or vision changes
- Persistent erections lasting more than 4 hours
- New breast lumps or tenderness
- Significant mood changes, especially depression or suicidal thoughts
The Bottom Line
Testosterone injections are an effective treatment for clinically diagnosed low T, but they’re not a casual prescription. The seven side effects above show up often enough that every man on therapy should know them by name, and bloodwork twice in the first year is the single best safety net you have. If anything on this list is happening to you, bring it up before your next injection rather than after. Talk to your prescriber or pharmacist about whether your current dose and schedule for testosterone injections still fit where your levels and symptoms actually are today.
This article is for informational purposes only and is not medical advice. Always consult a licensed pharmacist or physician before starting, stopping, or changing any medication.
References
- FDA: Testosterone Products Safety Communication, FDA labeling and cardiovascular risk warnings for testosterone therapy.
- Endocrine Society Clinical Practice Guideline on Testosterone Therapy, monitoring schedule and treatment recommendations.
- NIH/NCBI: Testosterone Replacement Therapy Overview, evidence summary on prostate, cardiovascular, and hematologic risks.
Dr Steven Schlosser
Dr. Schlosser graduated from Lafayette College Phi Beta Kappa and attended Georgetown Medical School. He had 4 years of medical residency training at Tufts University in Boston in both Gynecology and Internal Medicine. He has had a spotless medical career for the past 40+ years and is Board Certified. Learn More