Clomiphene citrate is a mixed-isomer SERM consisting of two stereoisomers: enclomiphene (trans-isomer, anti-estrogenic) and zuclomiphene (cis-isomer, weakly estrogenic). It has been the most widely used PCT compound alongside Nolvadex for decades. Clomid stimulates the HPTA by blocking estrogen negative feedback at the hypothalamus, driving increased GnRH, LH, and FSH secretion. It is particularly effective at raising FSH, which supports spermatogenesis — making it the preferred SERM when fertility preservation is a priority.
Notes
Clomiphene has been used off-label for male hypogonadism since the 1960s. The two-isomer composition is its biggest drawback — zuclomiphene's 30-day half-life causes progressive accumulation and worsening side effects. This is why enclomiphene (the isolated trans-isomer) has gained popularity as a superior alternative. However, Clomid remains widely available and affordable, making it the most accessible PCT SERM worldwide. At 25-50mg dosing, most users tolerate it reasonably well.
Clomiphene binds to estrogen receptors in the hypothalamus, displacing estradiol and blocking negative feedback. The hypothalamus responds by increasing GnRH pulse frequency and amplitude. This stimulates the anterior pituitary to release more LH and FSH. LH drives testicular testosterone production via Leydig cells, while FSH stimulates Sertoli cells to support spermatogenesis. The enclomiphene isomer is responsible for the desired anti-estrogenic SERM effects. The zuclomiphene isomer is weakly estrogenic and accumulates due to its extremely long half-life (~30 days), which is responsible for many of Clomid's mood-related side effects.
Rapidly absorbed orally with good bioavailability. Peak plasma levels in 3-6 hours. The two isomers have dramatically different pharmacokinetics: enclomiphene has a half-life of approximately 10 hours, while zuclomiphene persists for approximately 30 days. This means zuclomiphene accumulates significantly during a 4-week PCT, which explains why side effects often worsen in later weeks. Metabolized hepatically. Excreted primarily in feces.
Typical Dose
PCT: 50mg/day weeks 1-2, then 25mg/day weeks 3-4 (standard). Aggressive PCT: 100/50/50/25 or 50/50/25/25/25 over 5 weeks. Fertility protocol: 25-50mg/day or every other day long-term. On-cycle estrogen management: Not recommended (use an AI instead).
Frequency
Once daily. The long half-life of zuclomiphene means splitting doses is unnecessary.
Administration
Oral tablet, taken with or without food. Available in 25mg and 50mg tablets.
Half-Life
Enclomiphene: ~10 hours. Zuclomiphene: ~30 days (accumulates with repeated dosing)
Contraindications
Standard PCT: Start 2 weeks after last long-ester injection or 3 days after short-ester. Run 50/50/25/25 over 4 weeks. After 19-nors: Wait 3-4 weeks post-Deca or 2 weeks post-NPP. Use HCG bridge (1000-1500 IU EOD for 2 weeks) before starting Clomid. After heavy cycles: HCG bridge 2-3 weeks, then Clomid 50/50/50/25/25 over 5 weeks. Fertility-focused PCT: Clomid 25-50mg/day for 3-6 months with semen analysis monitoring every 3 months. Confirm recovery with bloodwork 4-6 weeks after cessation.