Skyla and Mirena are hormonal intrauterine devices (IUDs) that contain progestin levonorgestrel. The main difference between Skyla and Mirena is their implant duration. Mirena can also help treat heavy menstrual bleeding.

People with a Skyla IUD keep the device in place for up to 3 years, whereas those with a Mirena IUD keep it for 5–6 years.

In this article, we look at how they work and compare their effectiveness and potential side effects. We also discuss the insertion and removal processes.

An image depicting an IUD for an article comparing Skyla and Mirena.Share on Pinterest
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The following table summarizes the main differences between Skyla and Mirena:

PurposeHormoneDosageDuration of useSuccess rate
Treatment for heavy menstrual bleeding.
Progestin levonorgestrel20 mcg daily5–6 years99.3%
SkylaContraception.Progestin levonorgestrel14 mcg daily3 years99.1%

Skyla and Mirena are forms of hormonal IUDs that can help prevent pregnancy.


According to the National Library of Medicine (NLM), Skyla is an IUD that contains 13.5 milligrams (mg) of levonorgestrel.

People with this device receive 14 micrograms (mcg) per day of levonorgestrel after 24 days.

After 3 years, the dosage reduces to approximately 4 mcg per day. At this time, people should remove or replace the Skyla device.

The Food and Drug Administration (FDA) approve Skyla to prevent pregnancy for up to 3 years.


Similarly to Skyla, Mirena is an IUD that contains levonorgestrel. However, the NLM state that it has 52 mg of levonorgestrel.

Each day, the IUD releases 20 mcg.

After 5 years, the rate lowers to around 10 mcg daily, and after 6 years, it releases 9 mcg per day.

A person can also use Mirena to help treat heavy menstrual bleeding.

Both Skyla and Mirena release levonorgestrel into the uterus.

To prevent pregnancy, levonorgestrel-releasing IUDs:

  • thicken the mucus in the cervix, which prevents the passage of sperm into the uterus
  • cause the lining of the womb to become thinner

In some people, it also prevents ovulation.

Planned Parenthood state that IUDs are more than 99% effective.


The NLM say that the pregnancy rate in the 3 years of use was 0.9%, meaning Skyla has a 99.1% success rate.


The NLM state that two studies looking at 45,000 females in total found that pregnancy rates after 12 months’ use were less than or equal to 0.2%. Over 5 years, the pregnancy rate was roughly 0.7%. This means that Mirena has a success rate of 99.3%.

Since both IUDs release different amounts of the same hormone, the side effects are similar.

Common side effects include:

  • pain, bleeding, and dizziness during and after the insertion procedure
  • expulsion
  • missed menstrual periods
  • changes in bleeding patterns
  • ovarian cysts

Other potential side effects may include:

More serious side effects are rare, but may include:

According to a 2016 article, a major difference in side effects between Skyla and Mirena is the bleeding pattern.

Both IUDs may trigger unscheduled spotting and bleeding in the first 3–4 months. Loss of period or amenorrhea rates were much lower in people using Skyla compared with Mirena.

When to see a doctor

After insertion of either Mirena or Skyla, people should contact a healthcare provider if they:

  • think they are pregnant
  • have pelvic pain or pain during sex
  • have unusual vaginal discharge or genital sores
  • have unexplained fever, flu-like symptoms, or chills
  • might have a sexually transmitted infection
  • cannot feel the threads from the IUD
  • develop severe or migraine headaches
  • have yellowing of the skin or eyes
  • experience a stroke or heart attack
  • have a partner who tests positive for HIV
  • experience persistent and severe vaginal bleeding

The NLM state that, for both Skyla and Mirena, no drug interaction studies are available.

However, some drugs and herbal products may decrease the concentration of the progestin levonorgestrel hormone. These may include:

  • barbiturates
  • bosentan
  • efavirenz
  • carbamazepine
  • griseofulvin
  • felbamate
  • nevirapine
  • phenytoin
  • oxcarbazepine
  • rifampin
  • rifabutin
  • topiramate
  • St. John’s wort

Any drug or food product that inhibits or induces the metabolism of levonorgestrel may affect the amount of hormone in the blood.

A person can get an IUD from their local Planned Parenthood health center, or they can talk to a nurse or doctor.

Doctors or other healthcare professionals with specialized training may be able to perform insertion procedures for IUDs.

The insertion processes for Skyla and Mirena are similar.

What to expect

To start, the healthcare professional must confirm that the person is not pregnant and has no medical conditions that mean an IUD is unsuitable for them.

Before insertion

The person must position themselves in the lithotomy position, which means sitting with their legs flexed at 90 degrees at the hips. Stirrups help maintain this position.

Next, the medical professional will gently insert the speculum to see and cleanse the cervix.

They will then grasp the upper or lower lip of the cervix with forceps and apply traction to stabilize and align the cervical canal with the uterine cavity.

Before the insertion procedure, the medical professional will:

  • check the cervix
  • measure the depth of the uterine cavity
  • confirm the cavity direction
  • detect any uterine abnormalities

For Mirena IUD insertion, the uterus should measure 6–10 centimeters (cm). Inserting the Mirena into a uterus that measures less than 6 cm may increase the chance of:

  • expulsion
  • bleeding
  • pain
  • perforation
  • pregnancy

During the insertion

Once the doctor completes these first steps, a person is ready for the insertion process.

A doctor will ensure the device is sterile, before loading it into the insertion tube. They will use an inserter to implant and release the device into the correct area of the uterus.

The doctor will then cut the threads that are attached to the IUD to a certain length. Medical professionals will use these threads whenever they remove the device.

Doctors recommend removing and replacing Skyla after 3 years and Mirena after 6 years if people use them to prevent pregnancies. A person who uses Mirena to control menstrual bleeding should remove the IUD after 5 years.

The removal procedure is similar for both Mirena and Skyla.

Using forceps, a trained medical professional will gently pull on the IUD threads. If the medical professional cannot find them, the person may require an ultrasound to scan the pelvis.

How long until a person can become pregnant after removal?

A person can get the Skyla or Mirena removed at any time.

Skyla: A person can become pregnant as soon as a healthcare professional removes Skyla. Approximately 3 in 4 females will become pregnant within the first year of removal.

Mirena: A person can become pregnant as soon as a doctor removes the device. Approximately 8 in 10 females become pregnant within the first year of removal.

According to Planned Parenthood, an IUD can cost a person anywhere between $0–1,300.

However, many health insurance plans, some government programs, and Medicaid may cover the cost, or a portion.

Most Planned Parenthood centers will accept Medicaid and health insurance. Many centers will also charge less depending on a person’s income.

People might use Skyla or Mirena during breastfeeding if they gave birth more than 6 weeks ago.

According to the NLM, there may be small amounts of progestin in the breastmilk. However, there appear to be no reports of adverse effects in breastfed infants.

Researchers also demonstrate that starting an IUD immediately after giving birth is safe and effective, even while nursing.

Skyla and Mirena are IUDs that release levonorgestrel. The main difference between them is how much of the hormone they deliver.

Skyla releases 14 mcg every day while Mirena releases 20 mcg daily.

Each IUD has a different duration of action. People using Skyla should plan to remove and replace the IUD after 3 years if they wish to continue treatment.

People using Mirena should plan to remove and replace the device after 5 or 6 years, depending on its purpose.