If your testosterone is low, you have options. The two most common medical treatments are testosterone replacement therapy (TRT) and enclomiphene. They both raise testosterone, but they do it in fundamentally different ways, and those differences have major implications for fertility, side effects, and long-term management.
Here's what you need to know to make an informed decision with your provider.
How TRT works
Testosterone replacement therapy is exactly what it sounds like, you inject exogenous testosterone (typically testosterone cypionate) to directly replace what your body isn't producing enough of. It's the most straightforward approach: you put testosterone in, your levels go up.
TRT is typically administered as a weekly or biweekly intramuscular or subcutaneous injection. Dosing is individualized based on your lab results and response, usually starting around 100-200 mg per week and adjusted from there.
The results are predictable and often dramatic. Most men on TRT report improvements in energy, mood, libido, body composition, and cognitive function within 3-6 weeks. Testosterone levels can be precisely controlled through dosing adjustments.
The trade-off
When you introduce exogenous testosterone, your brain detects the elevated levels and shuts down your body's own production. The hypothalamus stops signaling the pituitary, LH and FSH drop, and your testes stop producing testosterone, and sperm. This is why TRT causes testicular atrophy and can cause infertility. For many men, this is reversible after stopping TRT, but not always, and recovery can take months.
How enclomiphene works
Enclomiphene takes the opposite approach. Instead of replacing testosterone from the outside, it stimulates your body to make more of its own.
Enclomiphene is a selective estrogen receptor modulator (SERM). It works by blocking estrogen receptors in the hypothalamus and pituitary gland. Normally, estrogen provides negative feedback that tells your brain to slow down testosterone production. By blocking that signal, enclomiphene tricks the brain into thinking estrogen is low, so it ramps up production of LH (luteinizing hormone) and FSH (follicle-stimulating hormone). LH tells the testes to produce more testosterone. FSH maintains sperm production.
The result: testosterone goes up, and fertility is preserved, or even improved.
Enclomiphene is taken as a daily oral pill, typically 12.5-25 mg. It's the trans-isomer of clomiphene (Clomid), isolated to reduce the side effects associated with the cis-isomer (zuclomiphene).
Head-to-head comparison
| Factor | TRT | Enclomiphene |
|---|---|---|
| Mechanism | Exogenous testosterone | Stimulates endogenous production via SERM |
| Administration | Weekly injection | Daily oral pill |
| T levels achieved | High, precisely controllable (600-1,000+ ng/dL) | Moderate increase (typically 200-400 ng/dL above baseline) |
| Fertility impact | Suppresses sperm production | Preserves or improves sperm production |
| Testicular size | Atrophy common | Maintained |
| LH / FSH | Suppressed to near zero | Elevated |
| Time to effect | 3-6 weeks | 4-8 weeks |
| Side effects | Polycythemia, acne, testicular atrophy, mood swings at peak/trough | Headaches (mild), visual disturbances (rare), mood changes |
| Lab monitoring | Total T, free T, hematocrit, PSA, estradiol every 3-6 months | Total T, LH, FSH, estradiol every 3-6 months |
| Stopping | Natural production may take months to recover (PCT often needed) | Natural production resumes quickly |
| Best for | Men needing maximum optimization, not concerned about fertility | Younger men, men planning children, those wanting natural production |
Efficacy: how much does each raise testosterone?
TRT wins on raw numbers. Because you're directly administering testosterone, levels can be dialed to virtually any target. Most men on TRT achieve levels of 600-1,000 ng/dL, and the dose-response relationship is predictable.
Enclomiphene typically raises total testosterone by 200-400 ng/dL above baseline. A man starting at 280 ng/dL might reach 500-650 ng/dL. That's clinically meaningful, often enough to resolve symptoms, but it has a ceiling. Enclomiphene can only get your body to produce as much testosterone as your testes are capable of making.
If your testes are functionally healthy but just understimulated (secondary hypogonadism), enclomiphene can work extremely well. If the testes themselves are the problem (primary hypogonadism), TRT is likely necessary.
The fertility question
This is the single biggest differentiator. TRT suppresses sperm production, often to zero. It has been studied as a male contraceptive. While fertility usually returns after stopping TRT, recovery can take 6-12 months, and in some cases it doesn't fully recover.
Enclomiphene preserves fertility because it maintains (and often increases) LH and FSH output. FSH is the hormone that drives spermatogenesis. Some fertility specialists actually prescribe enclomiphene to improve sperm counts in men trying to conceive.
If you're under 40 and think you might want children in the next 5-10 years, this is a critical consideration.
Side effects compared
TRT side effects
- Polycythemia, increased red blood cell production. Hematocrit must be monitored; if it gets too high (above 54%), blood donation or dose adjustment is needed.
- Testicular atrophy, testes shrink because they're no longer producing testosterone or sperm.
- Estrogen elevation, testosterone aromatizes to estradiol. Some men need an aromatase inhibitor.
- Acne and oily skin, especially at higher doses.
- Mood fluctuations, peak/trough cycling with injections can cause irritability.
Enclomiphene side effects
- Headaches, the most common side effect, usually mild and transient.
- Visual disturbances, rare, more associated with the older compound clomiphene (Clomid) than the isolated enclomiphene isomer.
- Mood changes, some men report feeling more emotional or irritable, though less common than with TRT.
- Elevated estradiol, because testosterone is going up, some of it aromatizes. Monitoring is important.
Can they be combined?
In some cases, yes. Some protocols use low-dose TRT with enclomiphene (or hCG) to maintain fertility and prevent testicular atrophy while still achieving higher testosterone levels. This is an advanced protocol that should only be managed by an experienced provider, but it's an option for men who want the best of both worlds.
Who should choose TRT?
- Men over 40 who are done having children
- Men with primary hypogonadism (testicular failure)
- Men who need maximum testosterone optimization for severe symptoms
- Men who have tried enclomiphene and didn't achieve adequate levels
- Men who prefer a weekly injection over a daily pill
Who should choose enclomiphene?
- Men under 40, especially those planning to have children
- Men with secondary hypogonadism (pituitary/hypothalamic cause)
- Men who want to maintain natural testosterone production
- Men who want to avoid injections
- Men with mild-to-moderate symptoms who may not need maximum-dose TRT
The bottom line
There is no universally "better" option. TRT delivers higher, more controllable testosterone levels but shuts down natural production and fertility. Enclomiphene preserves your body's own machinery and is gentler, but has a lower ceiling.
The right choice depends on your labs, your symptoms, your age, your fertility goals, and your personal preferences. A good provider will walk you through the trade-offs and help you make the call, and adjust the protocol based on how you respond.