The side effects most often reported with HRT are breast tenderness, bloating, headaches, mood changes, nausea and irregular bleeding. Each hormone has its own pattern, and the rarer serious effects, such as blood clots and stroke, need prompt medical attention no matter which hormone you take.
This guide puts the side effect lists side by side, explains the breast cancer and heart questions behind recent headlines, and gives you questions to bring to your clinician before you decide.
Estrogen HRT side effects
Menopause Specialists, a clinic that prescribes HRT, lists these estrogen-related effects: breast tenderness or enlargement, irregular bleeding or spotting, nausea, headaches and mood swings. The clinic says irregular bleeding typically resolves after a few cycles.
MedlinePlus’s estrogen and progestin patch page lists redness or irritation where the patch sits, headache, breast pain, nausea, back pain, and swelling of the hands, legs and feet. WebMD’s hormone therapy guide lists bloating, breast swelling or tenderness, headaches, mood changes, nausea and vaginal bleeding as reasons to call your doctor.
If you still have your uterus, estrogen alone carries a specific concern. A review hosted on PubMed Central notes that estrogen-only HRT in women with a uterus has been shown to increase the risk of overgrowth of the uterine lining. This is why people with a uterus are usually advised to add a progestogen.
Progesterone side effects and why clinicians weigh the type
Menopause Specialists lists progesterone-related effects as bloating, breast tenderness, and mood changes including anxiety, low mood and irritability. The clinic says progestogen type matters for clot risk. It says the potential elevated risk depends on the progestogen used and is generally not associated with body-identical micronised progesterone.
The PubMed Central review lists progestogen side effects as swelling and breast pain (more common with medroxyprogesterone acetate, or MPA), acne and hirsutism (more common with norethindrone), dizziness or fatigue, and adverse mood effects.
When progesterone is combined with estrogen, its main job is protecting the uterus. WebMD says taking progesterone with estrogen lowers your risk of endometrial cancer compared with taking estrogen alone. WebMD also says many experts now treat most menopausal patients with natural progesterone rather than synthetic progestins, and that research suggests natural progesterone may not have a negative effect on lipids.
These type-specific differences are what clinicians weigh when they choose a progestogen. Ask yours which type they chose and why.
| Effect | Estrogen | Progesterone or progestogen |
|---|---|---|
| Breast | Breast tenderness or enlargement (Menopause Specialists); breast swelling or tenderness (WebMD) | Breast tenderness (Menopause Specialists); swelling and breast pain, more common with MPA (PubMed Central review) |
| Mood | Mood swings (Menopause Specialists); mood changes (WebMD) | Anxiety, low mood, irritability (Menopause Specialists); adverse mood effects (PubMed Central review) |
| Bleeding | Irregular bleeding or spotting, typically resolving after a few cycles (Menopause Specialists); vaginal bleeding (WebMD) | Uterine bleeding with progestogen withdrawal in up to 80% of women on regimens that dose progestogens monthly (PubMed Central review) |
| Bloating, nausea, headache | Nausea and headaches (Menopause Specialists); bloating, nausea and headaches (WebMD) | Bloating (Menopause Specialists); dizziness or fatigue (PubMed Central review) |
| Skin and hair | The Menopause Specialists estrogen list does not include skin or hair effects | Acne and hirsutism, more common with norethindrone (PubMed Central review) |
| Clots | Transdermal estrogen does not appear to increase VTE risk the way oral estrogen does, though the only randomized trial comparing routes was too small to conclude (PubMed Central review) | Potential elevated risk depending on progestogen type; generally not associated with body-identical micronised progesterone (Menopause Specialists) |
Testosterone HRT side effects
Menopause Specialists describes testosterone as a component of HRT for women with low levels, used to address diminished libido. Its list of possible effects is below. The clinic says the British Menopause Society recommends testosterone blood tests before starting and again after 6 to 12 weeks.
| Possible effect | What the clinic says |
|---|---|
| Hair growth | May appear at the application site; the clinic suggests alternating the site daily |
| Acne and oily skin | Some women may notice more of both |
| Hair loss | Rarely, scalp hair loss (androgenic alopecia) |
| Clitoral enlargement | Generally reversible after stopping therapy |
| Libido changes | Shifts in sexual desire in some women |
| Mood changes | Irritability, mood swings or heightened aggression in some women |
| Cholesterol | May raise LDL and lower HDL; the clinic recommends monitoring liver and cholesterol function |
| Menstrual changes | Occasionally irregular or absent periods |
Clot risk is also discussed for testosterone. BodyLogicMD’s 2019 blog cites a study of men taking testosterone, which found venous thromboembolism risk 63% higher in the first six months of treatment, after which the risk declined. That is a finding in men. It does not describe women on low-dose testosterone. The blog says the increase corresponds to about 10 extra cases per 10,000 patients each year, and that the evidence is not conclusive.
On stroke, BodyLogicMD’s 2019 blog says the FDA requires a stroke-risk warning on prescription testosterone products; check the current label. The same blog says some data suggest men using injectable testosterone have a higher rate of stroke than men using patches or gels, and that there is currently no consensus on testosterone therapy and stroke risk in men.
Gender-affirming hormone therapy side effects
Your gender-care clinician can go through how side effects apply to your regimen. The only related items here are two points from Breastcancer.org about breast cancer risk and screening:
- Breastcancer.org says transgender men and non-binary people assigned female at birth who take testosterone have a lower breast cancer risk than cisgender women, but a higher risk than cisgender men.
- Breastcancer.org says trans women and AMAB non-binary people aged 40 and up, after five years on hormone therapy, should receive annual mammograms if they are otherwise at average risk.
Which HRT side effects are serious?
The MedlinePlus patch page quotes its boxed warning: combination hormone replacement therapy “may increase the risk of heart attack, stroke, blood clots in the lungs and legs, and breast cancer.”
Call your doctor immediately or get emergency care for any of these, according to the MedlinePlus page:
- Sudden, severe headache, or sudden, severe vomiting
- Changes in vision
- Hives, rash, itching, or difficulty breathing or swallowing
- Swelling of the face, throat, tongue, lips or eyes
- Severe pain in the upper abdomen that may spread to the back or chest
BodyLogicMD lists sudden and severe headache, slurred speech, blurry or dim vision, and dizziness, shortness of breath or fainting as symptoms to report to your doctor right away. It calls these rare, and says slurred speech needs immediate attention.
To report a serious side effect, you or your doctor can file with the FDA’s MedWatch reporting program.
Is HRT linked to breast cancer?
Breastcancer.org, updated January 8, 2026, reports that the FDA removed the “black box” warning from many HRT products in November 2025. The MedlinePlus patch page still shows a boxed warning. Check the warning on your own product label or ask your pharmacist which version applies.
Breastcancer.org’s main points:
- In women with no breast cancer history, systemic estrogen-only HRT is not linked to a higher risk of breast cancer, according to the Women’s Health Initiative studies and other research. In some groups, it appears to lower the risk.
- For combination HRT, the risk is higher if you begin more than 10 years after the onset of menopause or when you are older than 60.
- In women with a breast cancer history, a 2021 analysis of four studies found that women with hormone receptor-positive breast cancer who took systemic HRT had an 80% higher risk of recurrence than those who did not.
- A panel of experts published in the journal Menopause in September 2025 recommended that some women with a breast cancer history could choose systemic HRT after discussing risks and benefits with their doctor.
Can HRT affect heart and stroke risk?
In the Women’s Health Initiative trial, women aged 50 to 79, with a mean age of 63, taking oral conjugated estrogens with medroxyprogesterone acetate showed elevated cardiovascular event rates. The coronary heart disease hazard ratio was 1.29 (95% CI 1.02 to 1.63) and the stroke hazard ratio was 1.41, as reported in the PubMed Central review.
The same review summarizes that HRT has favorable or neutral effects on coronary heart disease risk when started in women younger than 60 or within 10 years of menopause, absent contraindications. It also notes that the type, formulation and route of HRT carry different side effects and risks.
Can HRT affect high blood pressure?
High blood pressure is on the list of conditions the MedlinePlus patch page asks you to tell your doctor about before you start. Tell your clinician if you have high blood pressure, and ask how it will be monitored.
BodyLogicMD’s 2019 blog says estrogen-only and combined HRT are both associated with an increased risk of ischemic stroke and hemorrhagic stroke. It notes hemorrhagic stroke is typically caused by high blood pressure. It also says that in a number of studies, transdermal and vaginal HRT were not associated with a higher risk of stroke.
Will progesterone make me gain or lose weight?
WebMD’s HRT guide covers hormone therapy as a whole, not progesterone alone. It says HRT doesn’t cause weight loss, at least not directly, but it might help with some weight issues indirectly. Better sleep and fewer hot flashes may make healthy habits easier to keep up.
On weight gain, WebMD says HRT could cause some bloating, but it is not known to cause weight gain. Some studies suggest HRT might redistribute abdominal visceral fat, but WebMD says this has not been proven for sure.
The WebMD guide does not compare the weight effects of progesterone and estrogen, and it does not say what progesterone alone does to weight. Ask your clinician about your weight goals.
No hormone is presented in these sources as a weight-loss treatment. Bring weight goals to your clinician.
Why do I feel so good on progesterone?
WebMD lists possible HRT benefits as relief from hot flashes and night sweats, better sleep, and less vaginal dryness. The sources do not explain why some people feel good on progesterone; ask your clinician. Mood changes are also a listed side effect, so keep a note of how you feel from week to week and share it at your appointments.
How long do HRT side effects last?
Menopause Specialists says most side effects are temporary and tend to fade as the body adjusts. For most women, effects are mild and fleeting and seldom last beyond a few weeks. The clinic says to contact it if side effects are hard to manage or last beyond three months from starting HRT or from any change in dose or type.
Irregular bleeding typically resolves after a few cycles, according to the clinic. Consult your clinician if it lasts beyond three months.
Our separate article on surprising side effects of apple cider vinegar is about apple cider vinegar, not HRT.
Who should not take HRT?
WebMD lists these as reasons to avoid HRT: a history of blood clots; cancer such as breast, uterine or ovarian; heart, liver or gallbladder disease; a heart attack; known or suspected pregnancy; and unexplained vaginal bleeding. It notes that a doctor may encourage you to stop smoking before prescribing HRT.
What are the long-term side effects of letrozole?
Ask the prescriber who started it, and read the prescribing information your pharmacy gives you.
HRT and the other options compared
Cleveland Clinic’s perimenopause guide says your provider may recommend antidepressants, birth control pills, HRT or hormone therapy, and that your provider will discuss the risks and benefits and recommend the best option based on your needs. The table below compares the options named in these sources.
| Option | What the sources say | Limits and notes |
|---|---|---|
| Systemic HRT (estrogen, or estrogen with progestogen) | Breastcancer.org calls it an effective treatment for menopausal symptoms, including hot flashes, night sweats, mood swings and vaginal symptoms | Combination HRT is usually taken by people who still have a uterus; the risks above apply |
| Vaginal estrogen | Low-dose creams, tablets or rings that mostly stay in vaginal tissue, improving dryness and discomfort during sex | Treats vaginal symptoms, not all menopausal symptoms (breastcancer.org) |
| Fezolinetant (Veozah) | WebMD says the FDA approved it in 2023 for moderate-to-severe hot flashes; it is not a hormonal medication | Ask your clinician whether it suits your history |
| Elinzanetant (Lynkuet) | WebMD describes it as a non-hormonal medicine for moderate-to-severe hot flashes that blocks NK1 and NK3 proteins | Ask your clinician about its side effects |
| Paroxetine (Brisdelle) | WebMD says it has been FDA approved for hot flashes | Antidepressant class |
| Other antidepressants (venlafaxine, desvenlafaxine) | WebMD says they may help hot flashes; Cleveland Clinic lists antidepressants as helping hot flashes, mood swings, anxiety or depression | Used under a clinician’s direction |
| Gabapentin and oxybutynin | Cleveland Clinic says each can relieve hot flashes; WebMD says gabapentin is usually prescribed for seizures and oxybutynin for urinary incontinence | Prescribed for other conditions first |
| Cognitive behavioral therapy and mindfulness | WebMD says CBT helps you adapt to hot flashes, and mindfulness may help you manage them | WebMD notes neither lowers how often hot flashes happen |
| Hypnosis and acupuncture | WebMD says the National Menopause Society recommends hypnosis to reduce how often and how severe hot flashes are; acupuncture may help, but WebMD says the research does not yet prove it | Evidence is still developing |
| Plant estrogens, black cohosh, vitamin E | WebMD says phytoestrogens from soy, chickpeas and lentils, and black cohosh and vitamin E, might help hot flashes | Ask your clinician before combining with other medicines |
| Bioidentical HRT | WebMD says some bioidentical hormones are made by drug companies and FDA approved, while others are compounded by a pharmacist after a prescription. BodyLogicMD says it is often considered less likely to be associated with adverse effects; Menopause Specialists makes a similar claim | WebMD cautions that not everything natural is necessarily safe, and that once a plant is processed, the product is no longer in its natural form |
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What is still not known?
- Menopause Specialists says predicting side effects can be challenging, because they depend on when you start, your hormone sensitivity, and the hormone type, dose and route.
- For testosterone and clots, BodyLogicMD says the evidence is not conclusive, and previous research with different methods found no relationship.
- Whether HRT changes visceral fat is not proven, according to WebMD.
- There is no consensus on testosterone therapy and stroke risk in men, according to BodyLogicMD.
Before you talk to your clinician
- Which hormone and which type or route do you recommend for me, and why?
- Does my blood pressure, clotting history, or cancer history change the choice?
- Which blood tests do you want, and when?
- What should I do if side effects last beyond three months?
- Which of my current medicines and supplements could interact with this treatment?
Cleveland Clinic suggests keeping a journal of your cycles, including when they start and stop and how much bleeding there is. Bring that journal, along with the dates of any side effects, to your appointment.
Our separate guide to vapofil side effects and medication interactions covers an herbal capsule supplement sold as a men’s health formula, not HRT.
By MeridianMedicalCentre.com Health Research Team
This article is for general information purposes only and does not constitute medical advice. Consult your doctor or qualified healthcare provider before making changes to your health routine.