Hot Flashes During Cancer Treatment
Hot flashes are one of the most common side effects of hormone therapy for breast and prostate cancer, and of treatments that bring on early menopause. They are not dangerous, but they can disrupt sleep, work and mood, and they are a leading reason people stop taking hormone therapy that lowers the chance of cancer returning. The good news: several non-hormonal treatments work, and you do not have to just put up with them.
Key Points
- Hot flashes affect most women on tamoxifen or aromatase inhibitors at some point, and most men on androgen deprivation therapy for prostate cancer.
- Hormone replacement therapy (estrogen) is usually not used after hormone receptor-positive breast cancer.
- Effective non-hormonal options include venlafaxine and similar antidepressants, gabapentin, oxybutynin, cognitive behavioral therapy and clinical hypnosis.
- If you take tamoxifen, avoid paroxetine and fluoxetine for hot flashes.
- A hot flash with fever, chills or feeling unwell may be an infection, not a hot flash. Check your temperature.
Understanding Hot Flashes
A hot flash is a sudden feeling of heat, usually in the face, neck and chest, that spreads through the body. It often comes with flushing (red skin), sweating, a fast heartbeat, and sometimes anxiety. It may be followed by chills as sweat cools. Hot flashes at night are called night sweats and can soak clothes and bedding.
Each hot flash usually lasts from 30 seconds to a few minutes. Some people have one or two a week; others have many each hour.
Why they happen
The brain's temperature control center, in an area called the hypothalamus, keeps body temperature within a narrow "comfort zone." Estrogen and testosterone help keep that zone steady. When these hormone levels drop suddenly, or their effects are blocked, the zone narrows. A tiny rise in core temperature then triggers the body's cooling response: blood vessels in the skin widen and sweating starts.
Research has found that certain brain cells (called KNDy neurons) become overactive when estrogen falls, using a signal called neurokinin B. This discovery led to newer non-hormonal medicines that block this signal.
Why they can be worse with cancer treatment
- Treatment-induced menopause is often sudden, while natural menopause happens over years.
- Hormone therapy for cancer is designed to lower or block hormones as completely as possible.
- The usual menopause treatment, estrogen, is generally not an option after hormone-sensitive cancer.
Which Cancer Treatments Cause Them
| Treatment | Used for | How often hot flashes occur |
|---|---|---|
| Tamoxifen | Breast cancer, risk reduction | Very common; reported by most women in prevention trials |
| Aromatase inhibitors: letrozole, anastrozole, exemestane | Breast cancer after menopause | Common; about 1 in 3 in major trials |
| Ovarian suppression (goserelin, leuprolide) or removal of ovaries | Breast cancer before menopause, ovarian cancer risk reduction, gynecologic cancers | Very common, often intense |
| Chemotherapy that stops periods | Many cancers in premenopausal women | Common; may be temporary |
| Androgen deprivation therapy (ADT): leuprolide, degarelix, relugolix, orchiectomy | Prostate cancer | Up to about 80% of men |
| Antiandrogens (bicalutamide, enzalutamide, apalutamide, darolutamide) and abiraterone | Prostate cancer | Common, especially with ADT |
| Fulvestrant | Advanced breast cancer | Common |
| Opioids, some antidepressants, steroids | Supportive care | Sweating or flushing in some people |
Some cancers can also cause sweating and flushing directly, for example lymphoma (drenching night sweats) and neuroendocrine tumors (flushing). New night sweats without an obvious treatment cause should always be mentioned to your doctor. Learn more about hormone therapy and its side effects.
How Severe Are They?
Cancer teams often grade side effects using the National Cancer Institute's Common Terminology Criteria for Adverse Events (CTCAE):
| Grade | Description | Typical approach |
|---|---|---|
| Grade 1 (mild) | Noticeable but not interfering with daily life | Lifestyle steps, cooling strategies |
| Grade 2 (moderate) | Interfere with everyday tasks such as work, shopping or housework | Add non-drug therapy (CBT, hypnosis) and/or medicine |
| Grade 3 (severe) | Interfere with basic self-care such as bathing, dressing or sleeping | Medicine plus non-drug therapy; review cancer treatment plan |
Research studies also use a hot flash score: the number of hot flashes per day multiplied by their average severity (1 = mild, 2 = moderate, 3 = severe, 4 = very severe). Keeping a simple diary (see Tracking) lets you and your doctor see whether a treatment is working.
What matters most is how much they bother you. Two hot flashes a night that wake you up can be more disabling than ten mild ones during the day.
Prevention and Everyday Steps
Hot flashes from hormone therapy usually cannot be fully prevented, but these steps can make them less frequent or easier to cope with. Evidence for most of them is limited, but they are low-risk.
Stay cool
- Dress in layers you can remove quickly; choose breathable cotton or moisture-wicking fabrics.
- Keep the bedroom cool; use a fan, light bedding, and a cooling pillow or mattress pad.
- Keep cold water nearby; sip it at the start of a hot flash.
- Carry a small hand fan or cooling spray.
Know your triggers
Common triggers include alcohol, caffeine, spicy food, hot drinks, hot rooms, smoking and stress. Triggers vary from person to person, so a diary can help you find yours.
Healthy habits
- Weight: In people with overweight, losing weight has been linked to fewer hot flashes.
- Stop smoking: Smoking is linked to more hot flashes and many other health problems.
- Physical activity: Exercise may not reduce hot flashes much, but it improves sleep, mood, fatigue, bone health and joint pain from aromatase inhibitors.
Timing your medicine
There is no good evidence that the time of day you take tamoxifen or an aromatase inhibitor changes hot flashes. Some people prefer a time that fits their routine and sleep; ask your pharmacist.
Medications That Help
If hot flashes bother you, there are non-hormonal medicines with good evidence. Most reduce hot flashes by roughly 50% to 65%, compared with about 20% to 30% from placebo. Your doctor will choose based on your other health conditions, other medicines, and whether you take tamoxifen.
| Medicine | Usual approach | Notes |
|---|---|---|
| Venlafaxine (Effexor XR) | Low dose, often 37.5 mg, may increase to 75 mg daily | Works within 1 to 2 weeks. Side effects can include nausea, dry mouth, constipation. Taper slowly when stopping. Safe with tamoxifen. |
| Desvenlafaxine (Pristiq) | Daily | Similar to venlafaxine |
| Citalopram, escitalopram | Low dose daily | Generally considered acceptable with tamoxifen |
| Paroxetine (low-dose Brisdelle is FDA-approved for menopausal hot flashes) | Daily | Avoid with tamoxifen; fine with aromatase inhibitors if appropriate |
| Gabapentin | Often started at bedtime and increased, up to about 900 mg/day in studies | Good for night sweats and sleep. Can cause dizziness and drowsiness; dose adjusted for kidney function. |
| Pregabalin | Daily | Similar to gabapentin |
| Oxybutynin | Low dose (2.5 to 5 mg) once or twice daily | Effective in trials including women with breast cancer. Dry mouth, constipation; long-term use may affect memory in older adults. |
| Clonidine | Pill or patch | Modest benefit. Can cause low blood pressure, dry mouth, drowsiness; must be stopped gradually. |
| Fezolinetant (Veozah) | 45 mg daily | Blocks the neurokinin-3 signal. FDA-approved for menopausal hot flashes. Has a boxed warning for liver injury; liver blood tests are needed before and during the first months. Limited data in people on cancer hormone therapy. |
| Elinzanetant (Lynkuet) | Daily at bedtime | Blocks neurokinin-1 and -3 signals. FDA-approved for menopausal hot flashes. Studied in women taking hormone therapy for breast cancer (OASIS-4). Ask your oncologist whether it suits you. |
Hormonal options and cancer
- Estrogen (hormone replacement therapy): Generally not recommended after hormone receptor-positive breast cancer, because it may increase the risk of recurrence. It may be an option after some other cancers; ask your oncologist.
- Progestins (megestrol acetate, medroxyprogesterone): Effective for hot flashes and used in men with prostate cancer. Usually avoided in women with breast cancer.
- Vaginal estrogen is used for vaginal dryness, not hot flashes. Its use with breast cancer hormone therapy should be discussed with your oncologist.
Tips for starting a medicine
- Give it a fair trial: most work within 2 to 4 weeks.
- If one medicine does not help or causes side effects, another may work.
- Do not stop venlafaxine, other antidepressants, gabapentin or clonidine suddenly; ask how to taper.
- Ask your pharmacist to check interactions with all your medicines.
Non-Drug Approaches
Approaches with good evidence
- Cognitive behavioral therapy (CBT): A short, structured talking therapy that changes how you respond to hot flashes. In trials including breast cancer survivors, CBT reduced how much hot flashes bothered people and improved sleep. It can be done in groups, one-on-one, or with guided self-help books and apps.
- Clinical hypnosis: Guided relaxation with suggestions of coolness, practiced with a therapist and at home. Trials in breast cancer survivors and postmenopausal women showed large reductions in hot flashes.
Approaches with mixed or limited evidence
- Acupuncture: Some trials in breast cancer survivors found benefit, others did not clearly beat sham acupuncture. It is low-risk with a licensed practitioner and some people find it helpful.
- Stellate ganglion block: An injection near nerves in the neck that has reduced moderate to severe hot flashes in some studies. It is a specialist procedure and not widely available.
- Yoga, mindfulness and paced breathing: May improve overall well-being and sleep even if they do not reduce the number of hot flashes.
Supplements
Most herbal and dietary supplements, including black cohosh, evening primrose oil, dong quai and vitamin E, have not consistently worked better than placebo in good trials. Some have plant estrogens or can interact with cancer drugs, and black cohosh has been linked to rare liver injury. Check with your oncologist or pharmacist before trying any supplement.
What to Avoid or Ask About First
- Paroxetine, fluoxetine and bupropion if you take tamoxifen (they may weaken it).
- Estrogen or hormone replacement therapy after hormone-sensitive breast cancer, unless your oncologist specifically recommends it.
- Concentrated soy isoflavone or red clover supplements. Normal amounts of soy foods (tofu, soy milk, edamame) are considered safe for breast cancer survivors.
- "Bioidentical" or compounded hormones sold for menopause: these are still hormones.
- Stopping your cancer hormone therapy on your own because of hot flashes. Talk to your team first; there are often solutions.
Hot Flashes in Men
Men treated with androgen deprivation therapy (ADT) for prostate cancer often have hot flashes, and many find them surprising. They can continue for as long as testosterone stays low and often ease after ADT stops, though in some men they last longer.
- Options with evidence in men: medroxyprogesterone acetate, megestrol acetate, venlafaxine, and gabapentin. Cyproterone acetate is used in some countries.
- Intermittent ADT: For some men with certain types of prostate cancer, ADT may be given in cycles with breaks. Ask whether this is appropriate for you.
- Lifestyle steps above apply equally to men.
- Men with breast cancer on tamoxifen also commonly have hot flashes.
Men on ADT should also ask about bone health, heart health, fatigue and mood. See hormone therapy for cancer.
Tracking Your Hot Flashes
A one- or two-week diary before and after any change helps you and your team decide what is working. Track:
- Date and time of each hot flash or night sweat
- Severity: mild, moderate, severe, or very severe
- Possible triggers (food, drink, stress, heat)
- Whether it woke you up
- Medicines and doses you took that day
- How much it bothered you overall (0 to 10)
Patient tips
- Keep a change of sleepwear and a towel next to the bed.
- Use layered bedding so you can push one layer off quickly.
- At work, a desk fan and a seat near a window or vent can help.
- Bring your diary to appointments; it makes the conversation quicker and more useful.
- If night sweats are ruining your sleep, also see our insomnia guide.
When to Seek Help
Check your temperature
A hot flash is not a fever. If you feel hot and have chills, shaking, a temperature of 100.4°F (38°C) or higher, or feel unwell, especially during chemotherapy, call your care team immediately or go to the emergency room. This may be an infection. See our fever guide.
Call 911 for chest pain or pressure, fainting, severe shortness of breath, or signs of stroke. These are not caused by hot flashes.
Contact your care team soon if:
- Hot flashes are disrupting your sleep, work or mood
- You are thinking about stopping your hormone therapy because of them
- You have drenching night sweats with weight loss or swollen glands
- You have a racing or irregular heartbeat outside of hot flashes
- You develop yellow skin or eyes, dark urine or belly pain while taking a new hot flash medicine (possible liver problem)
- You feel low, hopeless or anxious most days
More guidance: when to call your doctor during cancer treatment.
Frequently Asked Questions
Will my hot flashes go away?
For many people, hot flashes become less intense after the first few months of hormone therapy. They usually improve after treatment ends, though this can take months. If they stay bothersome, treatment can help at any point; you do not have to wait for them to fade.
Can I take hormone replacement therapy after breast cancer?
For hormone receptor-positive breast cancer, systemic estrogen is generally not recommended because it may increase the chance of the cancer returning. There are effective non-hormonal options. If your cancer was a different type, ask your oncologist whether hormone therapy is safe for you.
What is the best medicine for hot flashes on tamoxifen?
Venlafaxine is often a first choice because it works well and does not interfere with tamoxifen. Gabapentin, oxybutynin and citalopram or escitalopram are other options. Avoid paroxetine, fluoxetine and bupropion, which can lower the active form of tamoxifen.
Do aromatase inhibitors cause fewer hot flashes than tamoxifen?
In trials such as ATAC, hot flashes were somewhat less common with anastrozole than with tamoxifen, but they still affected about one in three women. Individual experience varies, and switching between drugs is not usually done for hot flashes alone.
Are Veozah (fezolinetant) or Lynkuet (elinzanetant) safe with breast cancer?
These newer non-hormonal medicines block brain signals that trigger hot flashes and are FDA-approved for menopausal hot flashes. Elinzanetant has been studied in women on hormone therapy for breast cancer. Fezolinetant requires liver blood tests because of a risk of liver injury. Ask your oncologist whether either is appropriate for you.
Do men get hot flashes from prostate cancer treatment?
Yes. Up to about 80% of men on androgen deprivation therapy get hot flashes. Options include medroxyprogesterone or megestrol, venlafaxine and gabapentin, along with the same cooling and lifestyle strategies women use.
Is it a hot flash or a fever?
A hot flash comes and goes within minutes and does not raise your measured temperature. A fever is a temperature of 100.4°F (38°C) or higher and may come with chills or feeling unwell. During chemotherapy, a fever is an emergency; call your care team right away.
Medical Disclaimer
This page is for education only and does not replace advice from your doctor, nurse or pharmacist. Do not start, stop or change any medicine without talking to your care team. In an emergency, call 911.
Sources and References
- National Cancer Institute. Hot Flashes and Night Sweats (PDQ®) – Patient and Health Professional Versions. cancer.gov. Accessed October 2026.
- National Cancer Institute. Common Terminology Criteria for Adverse Events (CTCAE), Version 5.0. 2017.
- The 2023 nonhormone therapy position statement of The North American Menopause Society. Menopause. 2023;30(6):573-590.
- National Comprehensive Cancer Network. NCCN Clinical Practice Guidelines in Oncology: Survivorship. Current version, accessed October 2026.
- Veozah (fezolinetant) [prescribing information, including boxed warning for hepatotoxicity]. U.S. Food and Drug Administration, DailyMed. Accessed October 2026.
- Lynkuet (elinzanetant) [prescribing information]. U.S. Food and Drug Administration, DailyMed. Accessed October 2026.
- Loprinzi CL, et al. Venlafaxine in management of hot flashes in survivors of breast cancer: a randomised controlled trial. Lancet. 2000;356(9247):2059-2063.
- Pandya KJ, et al. Gabapentin for hot flashes in 420 women with breast cancer: a randomised double-blind placebo-controlled trial. Lancet. 2005;366(9493):818-824.
- Leon-Ferre RA, et al. Oxybutynin vs placebo for hot flashes in women with or without breast cancer: a randomized, double-blind clinical trial (ACCRU SC-1603). J Natl Cancer Inst. 2020;112(2):375-382.
- Mann E, et al. Cognitive behavioural treatment for women who have menopausal symptoms after breast cancer treatment (MENOS 1). Lancet Oncol. 2012;13(3):309-318.
- Elkins G, et al. Randomized trial of a hypnosis intervention for treatment of hot flashes among breast cancer survivors. J Clin Oncol. 2008;26(31):5022-5026.
- Lyman GH, et al. Integrative therapies during and after breast cancer treatment: ASCO endorsement of the SIO clinical practice guideline. J Clin Oncol. 2018;36(25):2647-2655.
- Irani J, et al. Efficacy of venlafaxine, medroxyprogesterone acetate, and cyproterone acetate for the treatment of vasomotor hot flushes in men taking gonadotropin-releasing hormone analogues for prostate cancer: a double-blind, randomised trial. Lancet Oncol. 2010;11(2):147-154.