The best fertility drug for most women trying to get pregnant is letrozole, an oral medication that outperforms the older standard, clomiphene citrate, in both ovulation rates and live births. But “best” depends entirely on why you’re struggling to conceive. The right medication for someone who isn’t ovulating regularly differs from what works for someone with unexplained infertility, high prolactin levels, or a male partner with low sperm counts.
Letrozole vs. Clomiphene: The Two Main Options
Letrozole and clomiphene citrate are the two oral fertility medications prescribed most often, and head-to-head research favors letrozole. In a study of 750 women with polycystic ovary syndrome (PCOS), the most common cause of ovulation problems, letrozole produced a live birth rate of 27.5% compared to 19.1% for clomiphene. The ovulation rate was also higher: 61.7% versus 48.3%.
Both drugs work by tricking your body into producing more of the hormones that trigger egg development, but they do it differently. Clomiphene blocks estrogen receptors in the brain, which makes your body think estrogen is low and respond by ramping up the hormones that stimulate your ovaries. Letrozole temporarily reduces your actual estrogen production, creating the same hormonal signal but through a cleaner pathway. This difference matters because clomiphene’s estrogen-blocking effect can thin the uterine lining and thicken cervical mucus, both of which can work against implantation. Letrozole doesn’t have those drawbacks.
For women with PCOS specifically, letrozole is now the preferred first-line treatment. For unexplained infertility (when all the basic tests come back normal), the American Society for Reproductive Medicine recommends starting with three or four cycles of oral medication paired with intrauterine insemination before considering more intensive options. Both letrozole and clomiphene are used in this setting, though letrozole’s advantages in ovulation quality give it an edge for many doctors.
When Injectable Hormones Are the Next Step
If oral medications don’t work after several cycles, the next tier is injectable gonadotropins. These are lab-made versions of the same hormones your brain naturally sends to your ovaries: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Instead of nudging your body to produce more of these hormones on its own (which is what letrozole and clomiphene do), injectables deliver them directly.
Injectables are more powerful, which is both their advantage and their risk. They stimulate the ovaries more aggressively, so you’ll need regular ultrasounds and blood work to monitor how many follicles are developing. The multiple pregnancy rate with injectables is around 30%, or roughly 1 in 3 pregnancies. Compare that to about 8% (1 in 12) with clomiphene. That’s not just twins. Triplets and higher-order multiples carry serious risks for both the mother and the babies, including preterm birth and low birth weight.
Injectables are also the medications used during IVF cycles, where the goal is to develop many eggs at once for retrieval. In that context, the risk of carrying multiples is controlled by how many embryos are transferred back. A single embryo transfer drops the multiple pregnancy rate to around 3%.
Ovarian Hyperstimulation: The Risk to Watch For
Any medication that stimulates the ovaries can potentially cause ovarian hyperstimulation syndrome (OHSS), though it’s far more common with injectables than with oral drugs. Moderate to severe OHSS occurs in roughly 1% to 5% of IVF cycles.
Mild OHSS feels like bloating, mild nausea, and some abdominal discomfort. It’s unpleasant but resolves on its own. Moderate cases involve fluid buildup in the abdomen visible on ultrasound. Severe OHSS is a medical emergency with symptoms that include rapid weight gain (more than two pounds in 24 hours), difficulty breathing, very low urine output, and intense abdominal pain. Your fertility clinic will monitor you closely during any stimulated cycle to catch warning signs early. Women with PCOS are at higher risk because their ovaries tend to over-respond to stimulation.
Medications for High Prolactin Levels
If blood work reveals elevated prolactin, a hormone that suppresses ovulation, the treatment path is different. High prolactin is often caused by a small benign growth on the pituitary gland. The primary treatment is a class of drugs called dopamine agonists, with cabergoline being the most commonly prescribed.
Cabergoline normalizes prolactin levels and restores normal ovulation in about 80% of women within 6 to 12 months. It’s typically taken just once or twice a week as a pill, making it one of the simpler fertility treatments to manage. If ovulation still doesn’t return after prolactin levels normalize, clomiphene or other fertility treatments can be layered on top.
Fertility Medications for Men
Fertility drugs aren’t just for women. When male factor infertility is part of the picture, especially in men with low testosterone or hormonal imbalances, medications can significantly improve sperm production.
Clomiphene citrate works in men the same way it works in women: by boosting the brain’s signal to produce more reproductive hormones. For men, this translates to higher testosterone levels inside the testicles, which is where sperm are made. It’s often prescribed as a daily or every-other-day pill. Human chorionic gonadotropin (hCG), given as an injection, directly stimulates the testicles to produce testosterone and support sperm development.
These treatments are especially important for men who have been using testosterone replacement therapy, which can shut down sperm production almost entirely. Research shows that intratesticular testosterone levels drop by 94% in men on testosterone replacement alone. Switching to hCG can restore those levels and restart sperm production, with many men reaching a sperm concentration of around 22 million per milliliter within about four months. If sperm counts don’t recover with hCG alone after a few months, injectable FSH can be added to the regimen.
How to Think About Your Options
The “best” fertility drug is the one matched to your specific diagnosis. Here’s a practical framework:
- Not ovulating regularly (especially PCOS): Letrozole is the strongest starting option, with better live birth rates than clomiphene and fewer side effects on uterine lining.
- Unexplained infertility: Oral medication (letrozole or clomiphene) combined with intrauterine insemination for three to four cycles before escalating to injectables or IVF.
- High prolactin: Cabergoline to normalize hormone levels first, with fertility drugs added later if needed.
- Male factor (hormonal): Clomiphene and/or hCG injections to boost sperm production, with FSH added if initial treatment isn’t enough.
- No response to oral medications: Injectable gonadotropins, with close monitoring to manage the higher risk of multiples and ovarian hyperstimulation.
Most fertility specialists follow a “step-up” approach, starting with the simplest, lowest-risk treatment and escalating only when needed. For women under 38 with unexplained infertility, current guidelines don’t support jumping straight to IVF over a few cycles of oral medication with insemination. That less intensive approach works for a meaningful percentage of couples and costs a fraction of what IVF does. Age matters in this calculus, though. If you’re 38 or older, the timeline for stepping up treatment is often compressed because egg quality declines more steeply with each passing year.