Short answer: In the label's two controlled studies, the most common side effects with Estring were headache (13% vs 16% on conjugated estrogens vaginal cream), leukorrhea or vaginal discharge (7% vs 3%), back pain (6% vs 8%) and genital yeast infection (6% vs 7%). Ring-related reports include toxic shock syndrome, the ring sticking to the vaginal wall, vaginal erosion or ulcers, and bowel obstruction. This label version has no boxed warning.
What Estring is approved for: Estring is a soft vaginal ring holding 2 mg of estradiol that releases about 7.5 mcg per day over 90 days. It is approved to treat moderate to severe symptoms of vulvar and vaginal atrophy (dryness, irritation and thinning of vaginal tissue) due to menopause (Indications and Usage, Description).
Source
ESTRING (estradiol vaginal system) prescribing information (Physician's Leaflet) and Patient Information. Pfizer. DailyMed, version published April 27, 2026. DailyMed setid 110b9865-5a07-4d45-b560-e89947f12600
No. The current Estring label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Estring.
| Adverse event | Estring (n=257) % | Conjugated estrogens vaginal cream (n=129) % |
|---|---|---|
| Back pain | 6 | 8 |
| Arthritis | 4 | 2 |
| Arthralgia | 3 | 5 |
| Skeletal pain | 2 | 4 |
| Headache | 13 | 16 |
| Insomnia | 4 | 0 |
| Abdominal pain | 4 | 2 |
| Nausea | 3 | 2 |
| Upper respiratory tract infection | 5 | 6 |
| Sinusitis | 4 | 3 |
| Pharyngitis | 1 | 3 |
| Urinary tract infection | 2 | 7 |
| Leukorrhea | 7 | 3 |
| Vaginitis | 5 | 2 |
| Vaginal discomfort/pain | 5 | 5 |
| Vaginal hemorrhage | 4 | 5 |
| Asymptomatic genital bacterial growth | 4 | 6 |
| Breast pain | 1 | 7 |
| Genital moniliasis | 6 | 7 |
| Flu-like symptoms | 3 | 2 |
| Hot flushes | 2 | 3 |
| Allergy | 1 | 4 |
| Family stress | 2 | 3 |
The comparison is with conjugated estrogens vaginal cream, not placebo. Values are percent of patients.
Treatment was stopped because of an adverse event by 5.4 percent of patients on Estring and 3.9 percent on conjugated estrogens vaginal cream. The most common reasons on Estring were vaginal discomfort and gastrointestinal symptoms.
Endometrial overstimulation in the U.S. study was found in 0 of 58 patients (0 percent) on Estring and 4 of 35 (11 percent) on conjugated estrogens vaginal cream.
In the U.S. study, the physician's and patient's global assessments improved in 83 percent on Estring and 82 percent on cream after 12 weeks. Dysuria improved in 74 percent and urinary urgency in 65 percent of Estring patients.
For systemic estrogen-alone use, a meta-analysis of 24 studies reported a breast cancer relative risk of 1.33 with 5 to 14 years of current use, and a meta-analysis of 17 studies reported an ovarian cancer relative risk of 1.37. The label says the relevance of systemic estrogen risks to Estring is not known.
Reported after approval: toxic shock syndrome, ring adherence to the vaginal wall (some needing surgical removal), vaginal erosion and ulceration, bowel obstruction and hypersensitivity.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. Women with abnormal genital bleeding of unknown cause, known or suspected estrogen-dependent cancer, current or past DVT, pulmonary embolism, stroke or heart attack, a known anaphylactic reaction, angioedema or allergy to Estring, liver impairment or disease, or protein C, protein S or antithrombin deficiency or other clotting disorders.
Endometrial cancer. Systemic estrogen alone raises endometrial cancer risk in women with a uterus, about 2 to 12 times that of non-users, and 15- to 24-fold with 5 to 10 years or more of use. Persistent or recurring abnormal bleeding on Estring is checked, including endometrial sampling when indicated.
Systemic estrogen risks. Some estradiol from Estring is absorbed into the body, though less than from estrogens used for hot flashes, so how much the systemic risks apply is not known. The WHI estrogen-alone trial found more pulmonary embolism, DVT and stroke; other reported risks include gallbladder disease, high blood pressure reactions and pancreatitis with high triglycerides.
Ring-related problems. Toxic shock syndrome has been reported with vaginal rings. The ring has stuck to the vaginal wall, sometimes needing surgery to remove, and vaginal erosion or ulcers have occurred; the ring may be left out until healing is complete. Bowel obstruction has also been reported.
Ring moving or falling out. Some women have had the ring move within the vagina, or come out with bowel movements, straining or constipation. If this happens, the ring can be rinsed in lukewarm water and reinserted.
Irritation and infection. Estring may not suit women with a narrow, short or stenosed vagina; narrowing, prolapse and infections make irritation or ulcers more likely. Vaginal infections are treated before starting, and if one develops, the ring is removed until it has been treated.
Older women. In WHI studies of oral estrogen alone, women over 65 had a higher relative risk of stroke, and women 65 to 79 had a higher risk of probable dementia. It is unknown whether this applies to younger women.
From the Patient Information that comes with Estring:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.