A complete guide to IUDs, the extremely effective birth control method that lasts for years

• An IUD lasts for years and is more than 99% effective at preventing pregnancy.
• IUDs come in two main forms: hormonal and non-hormonal, with drawbacks and advantages to both.

An IUD, or intrauterine device, is a type of long-acting reversible contraception (LARC), and one of the most effective birth control options available.

In addition to having a failure rate of less than 1%, one of the biggest appeals of an IUD is that you can "set it and forget it," says Dr. Sophia Yen, CEO and co-founder of Pandia Health, a birth control delivery service.

Therefore, an IUD is a great option for those who don't want to deal with the hassle of other options like the pill, where you need to remember to take it around the same time every day for max protection.

Once inserted, an IUD can last anywhere from 3 to 10 years, depending on the type of IUD you get. And while these advantages sound great, the IUD has its fair share of downsides and side effects, just like any other birth control type.

Here's a look at the different types, how they work, and what to expect if you are considering this form of contraception.

How does an IUD work?

IUDs are small, T-shaped devices that a medical professional places in the uterus.

The device prevents pregnancy by making it harder for sperm to fertilize an egg, though the mechanism for how this happens depends on the IUD type — whether it's hormonal or non-hormonal.

Hormonal IUDs

Hormonal IUDs contain a synthetic form of the hormone progesterone called levonorgestrel, Yen says. Levonorgestrel works to prevent pregnancy by:

• Thickening cervical mucus, which makes it harder for sperm to enter the uterus.
• Preventing ovulation, or the release of an egg.
• Thinning the lining of the uterus to prevent implantation.

There are four types of hormonal IUDs that last between three and seven years. These include:

• Mirena, which contains 52 mg of levonorgestrel and lasts for seven years.
• Liletta, which also contains 52 mg of levonorgestrel and lasts for six years.
• Kyleena, which contains 19.5 mg of levonorgestrel and lasts for five years.
• Skyla, which contains 13.5 mg of levonorgestrel and lasts for three years.

While higher levonorgestrel doses last longer, the hormone does cause some side effects like headaches and dizziness. Therefore, people who are more sensitive to levonorgestrel may want to opt for an IUD with a lower hormonal dose.

Non-hormonal IUDs

Non-hormonal IUDs are made of copper and do not contain hormones. They can prevent pregnancy for up to 10 years after insertion.

The presence of copper works to prevent pregnancy by interfering with sperm movement, decreasing the chances of fertilization and implantation. That's because copper ions are toxic to sperm, Yen says

Paragard is the only non-hormonal IUD option in the US.

Note: Copper IUDs can function as emergency contraception. They can prevent a pregnancy when inserted within five days of unprotected sex.

IUD pros and cons

While everyone's reaction and preferences are different, these are a few common benefits and drawbacks that people may experience when they get an IUD.

How much does an IUD cost?

As part of the Affordable Care Act (ACA), IUDs should be available for free without a copay or deductible if you have health insurance, Yen says.

If you do not have insurance, the cost of an IUD is roughly $500 to $1,300, though this can vary depending on your provider, Yen says.

Most states also offer IUDs and other forms of contraception on a "sliding scale" under the Title X Family Planning program, which means you can get an IUD at a lower cost if you qualify based on your income, Yen says.

Can you get pregnant with an IUD?

Both hormonal and non-hormonal IUDs are more than 99% effective at preventing pregnancy. That means, fewer than 1 out of 100 people who get an IUD will get pregnant each year.

Moreover, "one of the greatest things about IUDs is that they remain highly effective over [the] whole time," they're inserted White says.

That said, it's still possible to get pregnant with an IUD, says Dr. Katie White, associate professor of OB-GYN at Boston University School of Medicine.

In some cases, if you become pregnant with an IUD it can result in life-threatening complications, like an ectopic pregnancy, which occurs when a fertilized egg implants itself outside the uterus, most commonly in one of the fallopian tubes. This can cause the fallopian tube to rupture, resulting in major internal bleeding.

Symptoms of an ectopic pregnancy typically include pelvic pain, vaginal bleeding, lightheadedness, fainting, and shock. Seek immediate medical attention if you think you're experiencing an ectopic pregnancy.

Note: The risk of an ectopic pregnancy is actually less with an IUD because the chance of pregnancy is so low. In other words, it's very unlikely that an IUD will cause an ectopic pregnancy.

How is an IUD inserted and does it hurt?

An IUD can be inserted by a doctor, nurse practitioner, or physician assistant, Yen says. The process only takes a few minutes.

Some providers will first numb the cervix and then apply some antiseptic, like iodine, to disinfect the area. Next, the provider will measure the length of your uterus and then insert the IUD.

You may feel some pain and discomfort during insertion and for a day or two afterward, Yen says. To manage this, Yen recommends these tips:

• Try to have the IUD inserted on the last few days of your period because your cervix is already open.
• Take 600 mg of ibuprofen (about three 200 mg tablets) with food half an hour before your appointment.
• Continue to take over-the-counter pain medication, per dosage guidelines on the package, if you experience cramps after insertion.
• Place a heating pad over your uterus to relieve pain from cramps.

Once your IUD is placed, there is a small risk of expulsion, or your IUD falling out. This occurs in about 2% to 10% of IUD users and is more likely when an IUD is placed immediately after having a baby.

Some doctors recommend avoiding penetrative sex within 48 hours after an IUD is inserted to keep it from coming out of place.

Signs your IUD might be out of place include:

• Not being able to feel your string
• Feeling the IUD
• New pain
• Abnormal bleeding

Quick tip: You can check to make sure your IUD is still in place by inserting a finger into the vagina toward the cervix. You should feel the IUD strings coming through the cervix.

IUD side effects

There are many IUD side effects and health complications to consider, depending on which IUD type you get.

Side effects of hormonal IUDs include:

• Acne
• Mood changes
• Changes in weight
• Irregular bleeding
• Nausea
• Shorter, lighter, or nonexistent periods. (For about 1 in 5 people using Mirena or Liletta IUDs, periods stop altogether after a year.)

Side effects of the non-hormonal copper IUD include:

• Spotting between periods or irregular periods
• Cramps or aches for a few days after insertion
• A heavier or longer period
• A more painful period

Insider's takeaway

An IUD is a small device placed in the uterus to prevent pregnancy that is more than 99% effective and can last between 3 to 10 years.

If you are considering an IUD, talk with your doctor about how long you would like your birth control to last, your health history, and which type of IUD is best for you.