Clomid (clomiphene citrate) stimulates ovulation by tricking your brain into producing more FSH. Per-cycle success rate: 8–12% for unexplained infertility, higher for anovulatory women. Typical protocol: 50–150 mg on cycle days 3–7 for up to 6 cycles. Common side effects: hot flashes, mood swings, headaches. Twin rate: about 8%. It's being increasingly replaced by Letrozole as first-line, especially for PCOS.
How Clomid Works
Clomid is a selective estrogen receptor modulator (SERM). It blocks estrogen receptors in the hypothalamus, tricking the brain into thinking estrogen is low. The brain responds by increasing GnRH, which stimulates more FSH release from the pituitary, which stimulates more follicle growth in the ovaries.
The result: instead of developing one follicle per cycle, you may develop two or three, increasing the target for sperm and improving per-cycle odds.
The Typical Clomid Protocol
| Step | Timing | What Happens |
|---|---|---|
| Start Clomid | Cycle days 3–7 (or 5–9) | Take 50 mg daily for 5 days. Dose may increase to 100–150 mg in subsequent cycles if needed. |
| Monitoring (optional) | Cycle days 10–14 | Ultrasound to count developing follicles and measure their size. Not all doctors monitor Clomid cycles. |
| Ovulation | Typically 5–10 days after the last pill | OPK testing recommended to confirm the surge; some doctors use a trigger shot (hCG injection). |
| Timed intercourse or IUI | Day of positive OPK + following 2 days | Standard fertile window timing applies. |
| Pregnancy test | 14 DPO | Standard timing. |
Success Rates
| Population | Per-Cycle Rate | Cumulative Over 6 Cycles |
|---|---|---|
| Anovulatory women (PCOS, etc.) | Ovulation achieved in 80%; pregnancy in 10–15% per cycle | 40–60% over 6 cycles |
| Unexplained infertility | 8–12% per cycle | 25–40% over 6 cycles |
| With IUI added | 12–15% per cycle | 35–50% over 6 cycles |
Side Effects
- Hot flashes (10–20% of women)
- Mood swings, irritability
- Headaches
- Visual disturbances (rare but report immediately — this is a reason to stop)
- Thinning of endometrial lining (anti-estrogenic effect on the uterus)
- Cervical mucus drying (reduced quality)
- Multiple pregnancy risk: ~8% twins, <1% triplets or higher
Clomid vs Letrozole
A landmark 2014 trial (NEJM) showed that Letrozole produces higher live birth rates than Clomid for PCOS patients (27.5% vs 19.1%). Letrozole also has fewer side effects on the endometrium and cervical mucus. Many REs now use Letrozole as first-line, with Clomid as backup. If your doctor starts with Clomid, ask whether Letrozole might be more appropriate for your situation.
Compare All Treatment Options
Our IUI vs IVF guide helps you understand the full treatment ladder.
Read the Decision Guide