Understanding Letrozole: A Guide to Its Use, Side Effects, and Diet

Many people hear the name letrozole for the first time at a stressful moment—often when discussing hormone-sensitive breast cancer treatment options. Understanding what the medication does, what changes you might feel, and how to support your body through treatment can make day-to-day decisions feel more manageable and informed.

How does letrozole work for breast cancer?

Letrozole belongs to a group of medications called aromatase inhibitors. Aromatase is an enzyme that helps the body make estrogen. By inhibiting aromatase, letrozole lowers estrogen levels in the bloodstream. This matters because many breast cancers are hormone receptor-positive, meaning estrogen can help cancer cells grow.

In the United States, letrozole is commonly used for postmenopausal women with hormone receptor-positive breast cancer, including after surgery (adjuvant therapy) and, in some situations, for more advanced disease. In premenopausal women, the ovaries can still produce significant estrogen; in those cases, an aromatase inhibitor may be used only with medical strategies that suppress ovarian function, if appropriate.

Letrozole is typically taken as an oral tablet once daily, often for multiple years depending on the treatment plan. Because the goal is sustained estrogen suppression, consistent daily dosing and regular follow-up appointments are central to how it is used in practice.

What are the side effects of letrozole?

Side effects vary widely: some people notice only mild changes, while others experience symptoms that affect sleep, mobility, or mood. One reason side effects occur is that estrogen plays roles throughout the body—not just in breast tissue—so lowering estrogen can influence temperature regulation, joints, bones, the vagina and urinary tract, and lipid levels.

Commonly reported side effects include hot flashes, night sweats, fatigue, joint or muscle aches, headache, and mild nausea. Some people notice vaginal dryness or discomfort, changes in libido, or mood changes. These effects can overlap with normal menopausal symptoms, which can make it harder to tell what is medication-related.

More clinically important concerns include bone density loss over time (osteopenia or osteoporosis) and fracture risk, because estrogen helps protect bone. Your clinician may recommend a baseline bone density scan (DEXA) and periodic monitoring, along with weight-bearing exercise and targeted supplementation if needed. Some patients also require prescription bone-protective medications based on individual risk.

You should contact a clinician promptly for symptoms that feel severe or unusual (for example, chest pain, shortness of breath, sudden swelling in a leg, fainting, or signs of an allergic reaction). While these are not typical day-to-day effects, urgent symptoms should be assessed rather than “waited out.”

What to avoid while taking letrozole?

One of the most important “avoid” categories is exposure to estrogen that could counteract treatment goals. This includes systemic estrogen therapies unless specifically directed by your oncology team. If vaginal symptoms are significant, discuss them—management options exist, and the safest approach depends on your cancer history and risk profile.

Medication interactions should be reviewed with a pharmacist or prescribing clinician, including over-the-counter products and supplements. For example, tamoxifen is generally not taken at the same time as letrozole because it can reduce the effect of aromatase inhibition. Also bring up any supplements marketed for “hormone balance,” menopausal support, bodybuilding, or fertility, as they may contain hormone-like ingredients.

From a diet perspective, there is no universal “letrozole diet,” but a few practical cautions are common. Avoid excessive alcohol intake because it can worsen hot flashes and sleep and may affect overall cancer risk management goals. If you use herbal products (such as concentrated botanical extracts), treat them like medications: some have estrogenic activity or can alter how the liver processes drugs. Because evidence and product quality vary, it’s safest to review any supplement with your care team.

Diet and lifestyle choices are often most helpful when they target known treatment issues: bone health, heart health, and inflammation-like symptoms such as joint stiffness. A balanced pattern that includes adequate protein, fiber-rich carbohydrates, and healthy fats can support energy and weight stability. Calcium and vitamin D needs vary; rather than self-prescribing high doses, ask for guidance based on your diet, labs (if checked), and bone density results.

If joint aches are a major issue, people sometimes find benefit from low-impact movement (walking, swimming, cycling), gentle strength training, and physical therapy strategies focused on mobility and stability. These approaches are not a substitute for medical evaluation, but they can be useful complements when symptoms affect function.

This article is for informational purposes only and should not be considered medical advice. Please consult a qualified healthcare professional for personalized guidance and treatment.

In many cases, the safest path is to treat letrozole as one part of a broader plan: regular follow-ups, lab and bone monitoring when recommended, symptom tracking, and open conversations about side effects and quality-of-life changes. With individualized care, many patients are able to stay on therapy while addressing side effects in a structured, evidence-based way.