New Side or Back Pain While Wearing a Menstrual Cup

New pain while wearing a menstrual cup belongs in the conversation with your healthcare provider. FDA advice is to stop using the cup and contact your provider if it causes pain, swelling or discomfort. A learning period for insertion does not make persistent pain something you have to tolerate.¹

What happened in a reported case

A 2025 report describes a 45-year-old woman with sudden, severe right-sided flank pain and nausea. Flank means the side of the body, around the back below the ribs. She did not report fever, painful urination or visible blood in her urine.²

A CT scan showed no kidney or ureteral stones. It did show swelling of the right kidney from obstructed drainage, called hydronephrosis. The authors described a malpositioned cup drawing adjacent tissues, including the ureter, toward it. The ureter is the tube carrying urine from a kidney to the bladder.²

Pain treatment and intravenous fluids had provided little relief. After clinicians reviewed the scan and asked her to remove the cup, her symptoms resolved immediately. She remained symptom-free when reassessed two hours later. Her creatinine, a blood measure used in assessing kidney function, had not been elevated.²

This is one patient’s course. It cannot establish that removing a cup will resolve another person’s pain, or that normal blood results exclude a drainage problem.²

How much does that tell us about risk?

A 2019 systematic review included 43 eligible studies involving 3,319 participants, alongside examination of adverse-event reports. It identified nine urinary-tract complaints, three involving hydronephrosis. Only three of the 22 studies included in its qualitative or quantitative syntheses were rated moderate-to-high quality.³

Those adverse-event counts are not a rate calculated from a population followed consistently for complications. Dividing three by 3,319 would give a misleading risk estimate. The review supported cups as a menstrual-management option while calling for better-quality research.³

Neither that review nor the single case identifies a brand, firmness or size that eliminates urinary obstruction.

Which symptoms should prompt care?

Hydronephrosis means a kidney is swollen by a buildup of urine. The NHS⁴ lists side, back or abdominal pain, difficulty peeing, blood in the urine and fever or shivering among possible symptoms, and advises urgent assessment. In the UK, its route is an urgent GP appointment or NHS 111. Elsewhere, use your local urgent-care service.⁴

If you cannot urinate or have severe abdominal pain, seek medical care right away. NIDDK gives that advice for possible acute urinary retention.⁵

Kidney stones and infections are among the other causes of blocked drainage. Wearing a cup does not exclude them. Do not delay assessment to keep experimenting with placement.⁴

Give the clinician a timeline

Alongside where the pain is and how severe it feels, mention:

• The cup’s brand and size, and when you inserted it.
• Whether this pain is new or different from your usual cramps.
• Any difficulty urinating, fever, nausea or visible blood.
• Whether the cup is still in place and any change after removal.

Follow the product’s removal instructions. If removal is difficult or painful, tell the healthcare team rather than repeatedly pulling at it. The FDA emphasizes following the manufacturer’s instructions and contacting a provider for pain or discomfort.¹

Period, Handled uses a Period Scorecard with entries for cup size and fill, timing and pain’s effect on daily life. Add the insertion and symptom times to those notes for the appointment. Recording details should not postpone urgent care. See the book.