The most effective options for triggering ovulation depend on why you’re not ovulating in the first place. Prescription medications like letrozole and clomiphene citrate are the strongest tools, with letrozole producing ovulation in about 62% of treatment cycles in women with polycystic ovary syndrome (PCOS). Supplements like inositol can also help restore ovulation for some women, particularly when insulin resistance is part of the picture. Here’s what works, how each option functions, and who benefits most.
Letrozole: The Current First-Line Prescription
Letrozole is now the preferred first-choice medication for ovulation induction in women with PCOS. It works by temporarily blocking the enzyme that converts androgens into estrogen. When estrogen drops, your brain responds by ramping up production of follicle-stimulating hormone (FSH), which is the signal that tells your ovaries to develop and release an egg.
A landmark trial published in the New England Journal of Medicine compared letrozole to clomiphene in 750 women with PCOS. Women taking letrozole had a cumulative live birth rate of 27.5%, compared to 19.1% for clomiphene. The ovulation rate per cycle was also higher at 61.7%. Letrozole is typically taken for five days early in your menstrual cycle, and your doctor will monitor follicle growth with ultrasound to confirm it’s working.
Clomiphene Citrate: The Long-Standing Option
Clomiphene (often called Clomid) has been used for decades and remains widely prescribed. It tricks your brain into thinking estrogen levels are low by blocking estrogen receptors, which triggers the same FSH surge that kickstarts follicle development. For many women, it works well, though letrozole has edged ahead as the preferred choice for PCOS specifically because of the higher ovulation and live birth rates seen in head-to-head comparisons.
Clomiphene is also taken for five days early in the cycle. Some women don’t respond to it, a situation called clomiphene resistance. When that happens, doctors often switch to letrozole or add other treatments.
Metformin for Insulin Resistance
If insulin resistance is contributing to your irregular cycles, metformin can help restore ovulation by improving how your body handles blood sugar. High insulin levels drive the ovaries to produce excess androgens, which disrupts the hormonal chain reaction needed for ovulation. By lowering insulin, metformin helps rebalance that chain.
The standard dosage is 500 mg three times daily, though some doctors prescribe 850 mg twice daily to make it easier to remember. Metformin is often used alongside clomiphene or letrozole rather than on its own, since the combination tends to produce better results than metformin alone. It can take several weeks to reach its full effect, so it’s typically started before you begin an ovulation medication cycle.
Injectable Gonadotropins
When oral medications don’t produce ovulation, the next step is usually injectable hormones that deliver FSH directly. These are the same hormones your body makes naturally, just given in controlled doses. The American Society for Reproductive Medicine recommends starting at a low dose of 37.5 to 75 IU per day, then increasing in small increments after seven or more days if no follicle reaches 10 mm on ultrasound.
This cautious “step-up” approach is designed to develop a single mature follicle rather than several, which reduces the risk of multiple pregnancies. Once a follicle reaches about 17 to 18 mm, a trigger shot (hCG) is given to release the egg. Follicles between 12 and 19 mm at the time of the trigger are most likely to produce a mature egg. Injectable cycles require frequent ultrasound monitoring, typically every few days.
Inositol: The Most Studied Supplement
Inositol is the supplement with the strongest evidence for improving ovulation, especially in women with PCOS. It comes in two forms that matter: myo-inositol and D-chiro-inositol. Your body uses both, but the ratio between them is important. A study comparing seven different ratios found that a 40:1 ratio of myo-inositol to D-chiro-inositol was the most effective at restoring ovulation and normalizing hormonal markers. When the ratio shifted to favor more D-chiro-inositol, results got worse.
The dosage used in clinical studies is typically 2 grams of combined inositol twice a day for at least three months. Inositol works by improving insulin signaling in the ovaries, which helps lower androgen levels and supports normal follicle development. Many fertility supplements now use the 40:1 ratio based on this research. It’s not as powerful as prescription medications, but for women with mild ovulatory dysfunction or as an add-on to other treatments, the evidence is encouraging.
Chasteberry for High Prolactin
If your irregular cycles are linked to elevated prolactin (a hormone that, when too high, suppresses ovulation), chasteberry extract may help. Compounds in chasteberry activate dopamine receptors in the pituitary gland, which puts the brakes on prolactin release. In one study, women taking chasteberry saw their shortened luteal phase normalize by about five days. Multiple studies have shown significant reductions in prolactin levels, and some case reports describe full normalization of menstrual cycles within three months.
Chasteberry is not a solution for all causes of anovulation. Its benefit is specific to women whose ovulation problems stem from mildly elevated prolactin. Women with very high prolactin levels or prolactin-secreting tumors need prescription dopamine agonists, which are far more potent.
CoQ10 and Egg Quality
Coenzyme Q10 (CoQ10) doesn’t directly trigger ovulation, but it supports the energy production eggs need to mature properly. A meta-analysis found that women with diminished ovarian reserve, particularly those under 35, benefited from CoQ10 supplementation with improved pregnancy rates. The optimal regimen identified was 30 mg per day started three months before a stimulated cycle. CoQ10 is often taken alongside ovulation-inducing medications rather than as a standalone approach.
NAC: Mixed Results as an Add-On
N-acetyl cysteine (NAC) is an antioxidant that has been studied as a partner to clomiphene for women who don’t respond to clomiphene alone. Early results looked promising: one trial found that adding 1.2 grams of NAC per day to clomiphene boosted ovulation from 1.3% to 49.3% in obese women with clomiphene-resistant PCOS. But later studies painted a less optimistic picture. When NAC was compared head-to-head with metformin as an add-on to clomiphene, metformin performed significantly better, producing ovulation rates of 69.1% versus 20% for the NAC combination.
NAC may offer some benefit for specific patients, but it’s not reliable enough to be a go-to option. If you’re considering it, it makes more sense as one piece of a broader plan rather than a primary strategy.
Choosing the Right Approach
What you should take depends heavily on the reason you’re not ovulating. PCOS is the most common cause of anovulation, and for that, letrozole with or without metformin is the strongest starting point. If your cycles are irregular because of high prolactin, chasteberry or prescription dopamine agonists are more targeted. For unexplained infertility, professional guidelines recommend starting with oral ovulation medications paired with intrauterine insemination for three to four cycles before moving to IVF.
Supplements like inositol and CoQ10 are reasonable additions, especially while waiting for a fertility workup or alongside prescribed treatments. But they’re unlikely to replace prescription medications for women with a clear ovulatory disorder. The first step is always identifying why ovulation isn’t happening, because that answer shapes everything that comes next.