Diaphragm or contraceptive cap

What is a diaphragm or cap?

It’s a small dome made of thin, flexible silicon that can be used as a barrier method of contraception by inserting it into your vagina. You use it with something called spermicide, a gel that kills sperm.

Cap or diaphragm effectiveness

Diaphragms and contraceptive caps are 92%-96% effective when used correctly 1 and every time you have sex. This means between 6 and 8 women in every 100 who are using it perfectly would get pregnant every year.

When they’re used typically, diaphragms and contraceptive caps are 71-88% effective. This means that around 12-29 users will get pregnant in one year 2. There are a few things that can make it less effective:

  • If it’s damaged.
  • If it doesn’t fit properly.
  • If you don’t use it with spermicide.
  • You have sex more than 3 hours after you put it in and didn’t use extra spermicide.
  • You take it out sooner than 6 hours after you had sex
  • You’ve been using bath oils, oil-based lubricants or vaginal medicines that can damage the silicon 3.

How do you insert a diaphragm or cap?

You’ll be fitted for your diaphragm or cap by a nurse or doctor. They will show you how to insert it.


When you come to put the diaphragm in yourself you can put it in up to 3 hours before you have sex. You can put it in earlier than that, but you’ll need to apply extra spermicide after 3 hours.

Wash your hands first and then rub a little spermicide gel on the upper side of the diaphragm.

Put your index finger (the finger next to your thumb) on top of the diaphragm. Hold the diaphragm between your thumb and other fingers.

Insert the diaphragm into your vagina upwards and backwards until it covers the cervix. Check your cervix is covered by feeling inside, it’s a small lump at the top. If you find your cervix isn’t covered, remove the diaphragm by hooking your finger under the rim or loop and pulling down. You can then try again.


Like the diaphragm, you can put the cap in up to 3 hours before you have sex. You can put it in earlier than that but you’ll need to apply extra spermicide after 3 hours.

Wash your hands and fill one third of the cap with spermicide. It’s important not to get any on the rim as this will prevent it staying in place.

Squeeze the sides of the cap together and hold it between your thumb and first two fingers. Slide the cap upwards into your vagina. It must fit over your cervix. The cap stays in place by suction.

Check that your cervix is covered every time you use it. If it isn’t, pull it back out by hooking your finger under the rim and pulling down and try again.

Depending on the type of cap, you may need to add extra spermicide after it has been put in.

Removing a cap or diaphragm

You must then leave the diaphragm or cap in until at least 6 hours after you’ve had sex. You can leave it in longer but it’s advisable to take it out within 30 hours. Hook your finger under the rim, loop or strap and pull it downwards.

When you’ve removed your diaphragm or cap, give it a wash with warm water and unperfumed soap and store it in a cool, dry place.

Advantages and disadvantages of this method

  • You can fit it before you have sex so don’t need to think about it in the moment. Equally, fitting it can interrupt the moment if you haven’t fitted it beforehand.
  • It only needs to be used when you have sex.
  • It’s non-hormonal so doesn’t affect your period.
  • Used correctly, there are no serious health risks associated with the cap or diaphragm as birth control.
  • Cystitis (bladder infections) can be a problem among some people using a diaphragm or cap.
  • Spermicide can be messy.

Things to consider before using a diaphragm or cap

  • A diaphragm doesn’t offer any protection against STIs, so you and your partner should get tested if you plan to use this alone. If you or your partner have other sexual partners, you may want to use condoms too.
  • If your weight changes by 7lbs or more, or you have a baby or miscarriage or abortion you might need to be fitted for a new cap. Talk to your doctor if this affects you.
  • You’ll need to apply extra spermicide if you have sex more than once.
  • They’re not suitable for use during your period as it can cause an increased risk of getting toxic shock syndrome.
  • It won’t be suitable for you if you or your partner are allergic to spermicide.
  • If you’re not comfortable touching your vagina, a diaphragm might not be suitable for you

Where can I get it for free?

You can get a free diaphragm from NHS sexual health clinics, contraception clinics, some young people’s services and most GP surgeries.

Other contraceptive options

You might prefer to use a contraceptive that doesn’t require as much planning as a diaphragm or cap. Long-acting reversible contraceptives include the intrauterine device, the intrauterine system, the contraceptive implant and the contraceptive injection. These require an appointment to fit or administer.

If taking or using something regularly is more suitable for you, and you want the ability to manage your periods, there are other options like the combined contraceptive pill, the progestogen-only pill (POP), the contraceptive patch and the contraceptive ring.

Reviewed by our clinical team: December 2020 (next review date: April 2022)

1. Source: Sexwise Diaphragms and caps - Contraception - Sexwise
2. Source: Sexwise Diaphragms and caps - Contraception - Sexwise
3. Source: NHS Contraceptive diaphragm or cap - NHS (www.nhs.uk)