Letrozole for Fertility: Why It Is Used, How It Works & Success Factors

Letrozole and Fertility: What to Expect Before You Begin

Difficulty with ovulation is one of the most common reasons for delayed conception, and letrozole is often prescribed when the ovaries need a reliable trigger to release an egg. Letrozole was originally developed to treat certain types of breast cancer. It was later discovered that it can also help the body to ovulate.

Letrozole offers a less invasive way to help the body release an egg, and for many, it is the first step before considering more advanced fertility treatments. In this guide, you will learn how letrozole works inside the body, why it is recommended by doctors, and who may benefit the most from the treatment. You will also learn what side effects to expect and how to prepare for each cycle.

What Is Letrozole and How Does It Work?

Letrozole is an aromatase inhibitor that helps stimulate ovulation in women who are not releasing an egg regularly. It is administered orally and frequently given to those with irregular cycles or conditions such as polycystic ovary syndrome (PCOS).

It works by temporarily decreasing oestrogen production. This change signals the brain to release more follicle-stimulating hormone (FSH) and luteinising hormone (LH), both of which are essential for egg development and ovulation.

Who Is Letrozole Suitable For?

Letrozole is often recommended for women who struggle to ovulate naturally. A fertility specialist may consider it if you:

• Have PCOS or irregular cycles where the ovaries are not releasing an egg regularly.
• Have unexplained infertility, when standard tests are normal, but pregnancy is still not occurring.
• Want an oral treatment instead of daily hormone injections.
• Prefer a lower chance of multiple pregnancies, since letrozole usually produces a single mature egg.

However, it isn’t the right option for everyone. Your doctor may avoid it if you have certain medical conditions, are already ovulating regularly or need a stronger treatment approach.

How Is Letrozole Taken During Fertility Treatment?

Letrozole is typically taken as a five-day course at the beginning of the cycle. Generally, the plan looks like this:

• Start the medicine between Day 2 and Day 5 of your period.
• Take one tablet each day for the following five days.
• Mid-cycle scan or home ovulation tests to check follicle growth.
• Timed intercourse or IUI, depending on the treatment plan.
• Pregnancy test about two weeks later.

Cycle monitoring may include:

• Ultrasound follicle tracking
• LH (luteinising hormone) surge detection
• Endometrial lining measurement
• Checking if ovulation occurred

Possible Side Effects of Letrozole

Letrozole can cause side effects, and some of them may feel similar to menopause because the medicine lowers oestrogen levels in the body. Speak to your doctor if any of the following symptoms are severe or do not settle:

• Hot flashes and night sweats
• Nausea, vomiting and loss of appetite
• Constipation, diarrhoea, heartburn or stomach pain
• Changes in weight
• Muscle, joint or bone pain
• Excessive tiredness, dizziness or general weakness
• Difficulty falling asleep or staying asleep
• Headache
• Breast pain
• Swelling of the hands, feet, ankles or lower legs
• Vaginal bleeding or irritation
• Hair loss
• Blurry vision

Some side effects can be serious. Seek urgent medical care if you develop:

• Chest pain
• Rash, hives or itching
• Difficulty breathing
• Unusual bleeding or bruising
• Pain in the upper right abdomen
• Flu-like symptoms
• Yellowing of the skin or eyes
• Pain, warmth or heaviness in the back of the lower leg
• A severe headache
• Sudden speech difficulty
• Sudden weakness or numbness in an arm or leg

What Are the Success Rates of Letrozole for Fertility?

Letrozole’s success rate varies, but many people see real improvements simply because their cycles become predictable again. Research has shown that around 27.5% of women taking letrozole achieve a live birth.

Among women with PCOS, up to 93% are able to ovulate on letrozole, which is one of the main reasons specialists often use it as a first-line treatment for ovulation induction.

Letrozole success highlights:

• Helps induce ovulation in a high percentage of cycles
• Often more effective than clomiphene for PCOS
• Works especially well when paired with timed intercourse or IUI (Intrauterine Insemination)
• Allows the body to ovulate more naturally than stronger medicines

Some conceive in the first cycle. Others need patience and a few rounds before seeing results. Both experiences are normal in fertility treatment.

Factors That Influence the Success Rate of Letrozole

A number of factors can influence how successfully letrozole supports ovulation. Some you can control; others depend on biology.

Key influencing factors include:

1. Age

With time, the ovaries don’t respond the way they used to. It’s a gradual change, but it does affect how well stimulation works.

2. Hormone Levels (AMH, FSH, LH)

These values help your doctor understand ovarian function. They help predict whether a healthy follicle is likely to grow.

3. Insulin Resistance

Higher insulin levels, especially common in women with PCOS, can interfere with normal ovulation. When insulin is better controlled, cycles often become more regular.

4. Body Weight and Metabolic Health

Even small improvements in metabolic health can help hormones settle into a more stable rhythm. The focus is on balance rather than achieving a particular number.

5. Stress Levels and Sleep Quality

Stress or disrupted sleep can interrupt the signals between the brain and the ovaries, making ovulation less predictable.

6. Follicle Response to the Chosen Dose

Some individuals respond well to the first prescribed dose of letrozole, while others may need an adjustment before ovulation becomes consistent.

Is Letrozole Safer or Better than Clomiphene?

Letrozole may be better for many people, but not for everyone. Reasons letrozole is often preferred are as follows:

• Less impact on the uterine lining.
• Less impact on cervical mucus.
• Lower chance of multiple pregnancies.
• More predictable response in PCOS.
• Fewer mood- or hot-flash-related side effects.

Why Clomiphene may still be used

• Works well for those who don’t respond to letrozole.
• Useful in certain fertility protocols.
• Familiar and widely available.

The “better” choice depends on individual response, medical history and the specific goal of the treatment.

When to Consult a Fertility Specialist?

It’s a good idea to speak with a specialist if you have been trying to conceive for a year (or six months if you are over 35). Anyone with very irregular periods, PCOS, thyroid concerns or known hormonal issues should get checked earlier.

Even if you’re simply curious about whether letrozole is right for you, a consultation can offer clarity. A doctor can look at your medical history, hormone levels and cycle patterns to guide you with confidence rather than guesswork.