HRT side effects: what is common, what is serious

Most side effects of hormone therapy are a nuisance rather than a danger: breast tenderness, spotting or irregular bleeding, bloating, nausea and headaches, which often ease within the first months or with a change of dose. The serious risks, blood clots, stroke, gallbladder disease and, with combined therapy, breast cancer, are real but uncommon in women who start in their 50s. This guide separates the two and gives the trial numbers for each.

Common side effects at a glance

The Menopause Society’s 2022 position statement lists the more common adverse effects as nausea, bloating, weight gain, fluid retention, mood swings (progestogen-related), breakthrough bleeding, headaches and breast tenderness. FDA labels show how often they occur compared with placebo:

Side effect	Estradiol gel 1.0 g a day, 12 weeks	Estradiol 1 mg with progesterone 100 mg, 1 year	Conjugated estrogen with cyclic progesterone 200 mg, 3 years
Breast tenderness	8.8% vs 1.6% placebo	10.4% vs 0.7%	27% vs 6%
Irregular bleeding	9.6% vs 1.6%	3.4% vs 0%	Not listed
Headache	Not listed	3.4% vs 0.7%	31% vs 27%
Nausea	Not listed	2.2% vs 0.7%	8% vs 7% (with vomiting)
Bloating	Not listed	Not listed	12% vs 5%
Depression	Not listed	Not listed	19% vs 12%
Dizziness	Not listed	Not listed	15% vs 9%

“Not listed” means the label did not report that effect at its threshold. The trials differ in length and in how they counted reports, so compare each row with its own placebo rather than across columns. Note also what these numbers do not show: in the 3-year trial, hot flashes were reported by 11 percent on treatment and 35 percent on placebo.

Bleeding and spotting

What to expect depends on the regimen. ACOG explains that cyclic therapy, with a progestogen added for 10 to 14 days a month, produces a planned monthly bleed. Continuous-combined therapy, with both hormones daily, aims for no bleeding but often causes irregular spotting at first. In the one-year trial of the estradiol and progesterone capsule, 56.1 percent of women on the higher dose and 67.6 percent on the lower dose reported no bleeding at all, versus 78.9 percent on placebo.

ACOG says spotting usually stops within 6 months. The Menopause Society advises investigating unscheduled bleeding that begins more than 6 months after starting combined therapy, and any bleeding after menopause needs evaluation. Women who take estrogen without a needed progestogen face a real risk: the estrogen-alone gel label keeps a boxed warning for endometrial cancer in women with a uterus.

Breast tenderness

This is the most consistent side effect and it tracks dose. On the estradiol gel it was reported by 2.5, 5.7 and 8.8 percent of women at the three doses studied, and on the combined capsule by 4.0 percent at the lower dose and 10.4 percent at the higher. The Menopause Society recommends the most appropriate, often lowest, effective dose, so a dose reduction is the usual first step.

Bloating, mood and drowsiness

Some effects are attributed mainly to the progestogen. The Menopause Society flags mood swings as progestogen-related, and in the 3-year trial of cyclic progesterone, depression, bloating and dizziness were all reported more often than on placebo. Micronized progesterone can also cause drowsiness, which is why its label directs a bedtime dose; see our guide to micronized progesterone. If progestogen effects are the problem, options include a different dose, schedule or progestogen, compared in progesterone vs progestin.

Weight

Weight gain is one of the most common worries and one of the least supported. The Menopause Society concludes that estrogen-progestogen therapy either has no effect on weight or is associated with less weight gain than in women not using it. In the WHI, women on hormones had a smaller increase in waist circumference over the first 3 years than women on placebo.

Skin and route-specific effects

Gels and patches can irritate the skin; in the estradiol gel trial, application site reactions occurred in fewer than 1 percent of women. Patch adhesion and skin reactions are covered in our guide to the estrogen patch.

The serious risks, in absolute numbers

The Menopause Society calls the serious risks of hormone therapy rare for women under 60. The revised 2026 labels give the WHI results for women aged 50 to 59, per 10,000 women per year:

Outcome	Estrogen plus progestin vs placebo	Estrogen alone vs placebo
Deep vein clot	15 vs 5	13 vs 8
Lung clot	11 vs 5	10 vs 6
Stroke	15 vs 10	16 vs 17
Coronary heart disease event	23 vs 17	17 vs 28
Invasive breast cancer	33 vs 27	24 vs 29
Death from any cause	21 vs 31	29 vs 40

In this age group, only the increase in deep vein clots with estrogen plus progestin was statistically significant; the other differences could be due to chance. The WHI tested one oral regimen, and risks rise with age and years since menopause. Our guides to whether hormone therapy is safe and breast cancer risk cover route, duration and older ages.

Gallbladder disease is more common than the other serious risks. Estrogen labels report a 2- to 4-fold increase in gallbladder disease requiring surgery, and The Menopause Society notes 47 extra self-reported cases per 10,000 women per year with estrogen plus progestin and 58 with estrogen alone in the WHI. Observational studies suggest less risk with transdermal estrogen.

Urinary leakage. The Menopause Society notes systemic hormone therapy may increase stress urinary incontinence; low-dose vaginal estrogen has been linked to less incontinence, not more.

Warning signs

The patient labeling for a revised estradiol and progesterone product asks women to call their healthcare provider right away for new breast lumps, unusual vaginal bleeding, changes in vision or speech, sudden new severe headaches, or severe pain in the chest or legs with or without shortness of breath. Labels also advise stopping estrogen if a clot, stroke or heart attack occurs or is suspected.

Managing side effects

ACOG advises talking with your ob-gyn if side effects trouble you or last longer than expected, because the dose can be adjusted. Useful questions:

• Could a lower dose control my symptoms with fewer side effects?
• Would a different route, such as a patch instead of a pill, suit me better?
• Is my bleeding pattern expected for my regimen, and when should it settle?
• Would a different progestogen or schedule help?

To find a clinician experienced with these adjustments, search our OB-GYN directory.