Menstrual cup dangers: This period product may affect your kidneys

Menstrual cups, a reusable alternative to period products like tampons and sanitary pads, have become quite popular over the past years. You just have to insert the small, flexible, bell-shaped cup into your vagina and it collects all the period blood. These cups which are usually made of medical-grade silicone or rubber can hold the fluid until they are emptied. You just have to follow simple steps to use this period product the right way. However, you may experience menstrual cup dangers if you don’t insert it properly. One of the problems is that it may block your urine flow and have a negative impact on your kidneys, medically known as ureterohydronephrosis.

Menstrual cup dangers: Know how it is linked to kidney problems

If you use a menstrual cup, make sure to insert it properly. When not done in the correct manner, it can lead to swollen kidneys and ureter, which is the tube that carries your pee away from the kidneys. “The swelling of the kidney and ureter is known as ureterohydronephrosis. It happens due to urine buildup, which is often caused by an obstruction. Chronic obstruction may damage your kidneys,” says gynaecologist Dr Ritambhara Bhalla.

In rare cases, improper use of a menstrual cup can contribute to this condition, which makes it difficult to urinate. A new study published in BMJ Case Reports in February 2025, showed that a woman in her 30s had intermittent pain in the side of her lower back, and occasional blood in urine. It was a rare case of ureterohydronephrosis connected to the period product. A scan of the urinary system showed that a menstrual cup was not properly placed in her vagina. After removal of the period product, researchers found that there was a complete regression of the symptoms.

Another study, published in Urology Case Reports in 2020, showed that a young woman experienced pain in the side of her lower back. It was found that she was using a menstrual cup. When it was removed, the pain vanished in one day. This was another rare case of ureterohydronephrosis due to an improperly positioned menstrual cup.

Here’s how using this period product can have a negative impact on your kidneys:

1. Compression of the urethra and bladder

A firm or large cup can press against your bladder and urethra. “If the cup sits too high or is inserted at an incorrect angle, it may apply pressure on the lower urinary tract, affecting urine flow,” shares Dr Bhalla. The obstruction can slow down or block urine flow, causing urine to back up into the ureters and kidneys. Over time, this pressure leads to swollen kidneys.

2. Increased suction and vaginal wall tension

The period product creates a vacuum seal to stay in place. Strong suction can pull on the vaginal walls, indirectly affecting nearby structures like the bladder and ureters. “This tension can restrict urine flow, leading to urinary retention and backflow into the ureters,” says the expert.

Other menstrual cup dangers

When used correctly, menstrual cup is safe, and effective. However, there are menstrual cup dangers when used improperly.

1. Suction-related injuries

Pulling the cup without breaking the seal can cause vaginal soreness, one of the menstrual cup side effects. It can cause pain, cramping, or difficulty inserting the cup later. “Always pinch the base or insert a finger to break the seal before removing the cup,” says Dr Bhalla.

2. Bacterial vaginosis

It is an infection that happens when the levels of bacteria in your vagina are out of balance. It leads to vaginal discharge with a fishy smell, and causes discomfort down there. “It is one of the menstrual cup dangers, especially if you wear it for more than 12 hours,” says the expert.

3. Toxic Shock Syndrome

One of the menstrual cup dangers is toxic shock syndrome. It is a life-threatening condition caused by bacteria Staphylococcus aureus and Streptococcus pyogenes. In rare cases, menstrual cups can also lead to toxic shock syndrome, according to research published in IDCases in 2021. “You may experience fever, rash, nausea, vomiting, and flu-like symptoms if you have Toxic Shock Syndrome due to using a menstrual cup for long,” says Dr Bhalla.

4. Vaginal or cervical irritation

A large or improperly positioned cup can cause pain, cramping, or discomfort down there. If it is inserted too high, it may press against your cervix, and cause spotting or irritation,” says the expert. Choose the right size based on your cervix height and flow to avoid menstrual cup dangers.

Menstrual cup dangers: How to use it correctly?

You can avoid menstrual cup dangers by using it correctly.

1. Choose the right cup

• Small cups are for teenagers, first-time users, or women with light flow.
• Large cups are for women who have given birth or have a heavy flow.
• Soft cups are perfect for you if you have bladder sensitivity or discomfort with firmer cups.
• Firm cups tend to stay in place better and may be easier to insert.
• If you have a low cervix, a shorter cup is better.

2. Inserting the cup correctly

• Wash your hands properly then rinse the cup with warm water.
• Sterilise it by boiling it for five minutes before first use and after each menstrual cycle.
• Sit on the toilet, squat, or place one leg on an elevated surface.
• Relax your pelvic muscles to make insertion easier, and avoid menstrual cup dangers.
• Fold the period product in half to create a “C” shape.
• Push one side of the rim into the cup for a smaller tip.
• Fold one side down diagonally into a “7” shape.
• Hold the folded cup and gently insert it into your vagina at a slight 45-degree angle towards your tailbone.
• Let it pop open inside and create a seal against your vaginal walls.
• Run a finger around the rim to ensure it is fully open.
• Gently rotate or wiggle the base to improve the seal.
• If inserted correctly, you should not feel the product.

3. Removing the cup

• Again, wash your hands before removing this period product.
• Pinch the base or insert a finger alongside the cup to release the seal.
• Do not pull it out by the stem alone to avoid discomfort or suction damage.
• Empty, rinse, and reinsert if you wish to use it again.

Menstrual cup dangers may be because you are not using it the right way or wearing it for long hours. “It can be worn for 6 to 12 hours, but you need to empty every 4 to 8 hours if you have a heavy period flow,” says the expert.

Ill-fitting menstrual cups can lead to ureterohydronephrosis by blocking your pee flow. There are more menstrual cup dangers, including Toxic Shock Syndrome. So, choose the right size, firmness, and shape while buying these cups, and position them correctly to prevent health problems.