Raloxifene is a prescription medication used primarily for two purposes: protecting bone density in postmenopausal women and reducing the risk of invasive breast cancer. It belongs to a class of drugs called selective estrogen receptor modulators, or SERMs, which mimic estrogen’s effects in some tissues while blocking them in others. The standard dose is 60 mg once daily, taken as a tablet with or without food.
How Raloxifene Works in the Body
After menopause, declining estrogen levels leave bones vulnerable to thinning and raise the cumulative risk of breast cancer. Raloxifene addresses both problems by acting like a key that fits into estrogen receptors differently depending on the tissue. In bone, it behaves like estrogen, stimulating the processes that maintain bone density. In breast tissue, it does the opposite, blocking estrogen from connecting with breast cells and keeping them from multiplying. This dual action is what makes SERMs useful for more than one condition at the same time.
Unlike hormone replacement therapy, raloxifene does not stimulate the uterine lining. That distinction matters because it means raloxifene doesn’t increase the risk of endometrial cancer, a concern with some other estrogen-related treatments.
Osteoporosis Prevention and Treatment
Raloxifene’s longest-standing use is for osteoporosis in postmenopausal women, both to prevent bone loss before it becomes severe and to treat it once diagnosed. The drug slows the breakdown of bone tissue, helping maintain the structural integrity that prevents fractures.
The clearest benefit shows up in the spine. In a four-year clinical trial, women taking the standard 60 mg daily dose had a 36% lower risk of new vertebral fractures compared to those on placebo. By the fourth year alone, that risk reduction reached 39%. These are meaningful numbers for women whose spinal fractures can lead to chronic pain, loss of height, and reduced mobility. The U.S. Preventive Services Task Force notes that raloxifene specifically reduces vertebral fractures, though the evidence for hip and other non-spinal fractures is less robust.
Breast Cancer Risk Reduction
In 2007, the FDA approved raloxifene for a second purpose: lowering the risk of invasive breast cancer in two groups of postmenopausal women. Those with osteoporosis (who may already be taking the drug) and those identified as high risk for breast cancer, typically meaning their risk is equivalent to or greater than that of an average woman between ages 60 and 64. Women previously diagnosed with lobular carcinoma in situ, a condition that signals elevated breast cancer risk, also qualify.
The landmark STAR trial compared raloxifene head-to-head with tamoxifen, the older standard for breast cancer prevention. After nearly seven years of follow-up, raloxifene reduced invasive breast cancer risk by about 38%, while tamoxifen reduced it by about 50%. That makes raloxifene roughly 76% as effective as tamoxifen for this purpose. A separate analysis conducted for the USPSTF found that raloxifene prevented about 9 cases of invasive breast cancer per 1,000 women treated over five years compared to placebo.
There are clear limits to this use. Raloxifene is not approved to treat existing breast cancer, reduce the chance of breast cancer coming back after treatment, or lower the risk of non-invasive forms like ductal carcinoma in situ (DCIS). It is a prevention tool, not a treatment.
The USPSTF currently gives a grade B recommendation for offering risk-reducing medications like raloxifene to postmenopausal women at increased breast cancer risk who are at low risk for side effects. For women not at increased breast cancer risk, these medications are not recommended.
Common Side Effects
The most frequently reported side effects are hot flashes, leg cramps, swelling of the feet and ankles, joint pain, flu-like symptoms, and sweating. Hot flashes tend to be most noticeable during the first six months of treatment and often ease after that. For women already dealing with menopausal hot flashes, this can be a frustrating overlap, but it typically improves with time.
Leg cramps and joint pain are generally mild but worth tracking. Swelling in the lower legs can sometimes be confused with more serious circulatory problems, so any sudden or severe swelling deserves a call to your doctor.
Serious Risks to Know About
Raloxifene carries an FDA black box warning, the most serious type, for two risks: blood clots and stroke-related death.
The blood clot risk includes deep vein thrombosis (clots in the legs) and pulmonary embolism (clots that travel to the lungs). Compared to placebo, raloxifene is associated with about 7 additional cases of venous blood clots per 1,000 women over five years. This is why the drug is contraindicated in anyone with a current or past history of blood clots, including clots in the retinal veins of the eye.
The stroke warning comes from a trial in postmenopausal women who already had coronary heart disease or were at high risk for major heart events. In that population, raloxifene was linked to a higher risk of fatal stroke. Notably, raloxifene has not been shown to increase rates of stroke overall, heart disease events, or endometrial cancer in the general postmenopausal population. The concern is specific to women with existing cardiovascular risk factors, and doctors weigh this carefully when prescribing.
Who Should Not Take Raloxifene
Raloxifene is approved only for postmenopausal women. Premenopausal women should not take it for any reason. It is classified as Pregnancy Category X, meaning it can cause harm to a developing fetus, and it should not be used while breastfeeding.
Beyond pregnancy and nursing, the main contraindication is a history of blood clots. If you have ever had deep vein thrombosis, a pulmonary embolism, or a retinal vein clot, raloxifene is not an option. Women who are about to have surgery or expect prolonged immobility (long flights, bed rest after a procedure) should also discuss timing with their doctor, since immobility itself raises clot risk.