How Does an IUD Work? Understanding the Mechanism

Amoha Jha
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how does an iud work

In recent years, Intrauterine Devices (IUDs) have become increasingly popular as a reliable and long-term contraceptive option for many women. 

But have you ever wondered how does an IUD work?

How do these tiny devices, once inserted into the uterus, effectively prevent pregnancy? 

If you don’t have an answer now, don’t worry, as we will delve into the intricacies of how an IUD works in this article.

We will also discuss other aspects of IUD working for more efficient usage and benefits.

How does an IUD work as a contraceptive

IUDs come in two main types: hormonal and non-hormonal (copper). 

While both serve the ultimate purpose of preventing pregnancy, they achieve this goal through distinct mechanisms.

Hormonal IUDs

Strings too shortSource: SOMNATH_MAHATA_from_GettyImages
Copper IUD

Hormonal IUDs are equipped with a small reservoir of synthetic Progestin hormone, typically Levonorgestrel. 

This hormone is slowly released into the uterus over time, providing a localized effect. 

The key mechanisms through which hormonal IUDs work as contraceptives include:

Thickening of cervical mucus

Progestin thickens the cervical mucus, creating a formidable barrier that stops the progress of sperm. 

This makes it more difficult for sperm to travel from the vagina into the uterus and fallopian tubes.

Inhibition of ovulation

In some cases, hormonal IUDs may suppress ovulation, preventing the egg from leaving the ovaries. 

Without an egg, fertilization cannot occur.

Alteration of the endometrial lining

The hormonal influence may result in changes to the endometrial lining of the uterus. 

This alteration may make it less receptive to a fertilized egg, reducing the likelihood of successful implantation.

However, more research is needed to determine the same.

Also Read: To learn more about different types of IUDs, read our article “A Comprehensive Guide to IUD Types: Finding Your Ideal Contraceptive”.

Non-hormonal IUDs (copper IUDs)

Unlike their hormonal counterparts, non-hormonal IUDs use copper as their active ingredient. 

Copper IUDs work as contraceptives through various mechanisms:

Toxicity to sperm

Copper has a toxic effect on sperm, impairing their motility and ability to reach the egg. 

This reduces the likelihood of successful fertilization.

Preventing fertilization

Copper changes the lining of the uterus and cervical mucus.

This interferes with the process of fertilization, further ensuring contraceptive efficacy.

Do you know?
Copper IUDs, in addition to serving as a highly effective long-term contraceptive method, also possess the capacity to function as a reliable form of emergency contraception when inserted promptly after unprotected intercourse.

How long can an IUD work

MirenaSource: luigi_giordano_from_Getty_Images
Doctor holding Mirena

The duration of effectiveness for both hormonal and non-hormonal IUDs is as follows:

Hormonal IUDs

Hormonal IUDs, such as Mirena, Skyla, Kyleena, and Liletta, slowly release Progestin into the uterus over time. 

The duration of effectiveness for hormonal IUDs varies depending on the brand:

  • Mirena: Up to Eight years
  • Kyleena: Up to five years
  • Skyla: Up to three years
  • Liletta: Up to six years

Non-hormonal IUDs

Non-hormonal IUDs, such as ParaGard, are wrapped in copper wire. 

The duration of effectiveness for copper IUDs is typically longer compared to hormonal IUDs.

ParaGard is effective for up to 10 years. 

It does not contain hormones and relies solely on the contraceptive effects of copper.

How to make IUDs work more efficiently

Intrauterine Devices are hailed as one of the most effective forms of contraception available today, offering women long-term protection against pregnancy with minimal effort. 

However, there are ways to optimize their efficiency further and ensure maximum effectiveness. 

Whether you’ve opted for a hormonal or non-hormonal IUD, here are some strategies to help you make the most of this highly reliable birth control method.

Ensure proper insertion

The first step to ensuring the efficiency of your IUD is to ensure it’s properly inserted by a trained healthcare provider. 

A correctly placed IUD will sit securely in the uterus, with its arms expanded and strings positioned appropriately. 

This minimizes the risk of IUD expulsion (unintended falling out of IUD) and ensures that the device can effectively deliver its contraceptive effects.

Self-insertion of IUDs poses risks, such as infection, perforation, improper placement, etc., compromising contraceptive effectiveness and personal safety. Thus, IUD insertion must be performed exclusively by a qualified healthcare provider. 

Regularly check the strings

After your IUD is inserted, it’s essential to periodically check the strings to ensure that the device remains in place. 

You can do this by inserting a clean finger into your vagina and feeling for the strings protruding from your cervix.

If you’re unable to feel the strings or if they seem shorter or longer than usual, contact your healthcare provider, as this could indicate a problem with the placement of the IUD.

Also Read: If you want to learn more about the displacement of an IUD, read our article “Displaced IUD: Signs, Symptoms, Causes and Solutions”.

Consider regular check-ups

Woman taking consultation from a doctorSource: Getty_images
Woman taking consultation from a doctor

Even though IUDs are long-lasting contraceptive options, it’s still a good idea to schedule regular check-ups with your healthcare provider. 

During these appointments, your provider can assess the placement of your IUD, address any concerns or side effects you may be experiencing, and discuss your overall reproductive health. 

Regular check-ups can help ensure that your IUD continues to work efficiently and effectively for the duration of its lifespan.

Recommended Article
IUDs have always been hailed for their effectiveness, but can you still get pregnant? 
Find the answer in our informative article “Getting Pregnant with IUD: Symptoms, Risks, and Guidance”.

How soon will my IUD start working

Paragard, Mirena, and Liletta IUDs initiate contraception immediately upon insertion. 

For Kyleena and Skyla, immediate protection occurs if inserted within the initial 7 days of menstruation. 

If inserted at other times, protection starts after 7 days, necessitating alternative contraception during the interim to prevent pregnancy.


Understanding how an IUD works is crucial for women seeking reliable contraception. 

Hormonal IUDs function by thickening cervical mucus, inhibiting ovulation, and altering the endometrial lining. 

On the other hand, non-hormonal copper IUDs, such as ParaGard, utilize copper’s toxicity to sperm and interference with fertilization. 

Both types offer long-term protection, with hormonal IUDs lasting up to eight years and copper IUDs for up to ten years. 

To optimize efficiency, ensuring proper insertion, checking strings regularly, and attending scheduled check-ups are essential. 

With these strategies, women can confidently rely on IUDs for effective birth control and reproductive health management.

Frequently Asked Questions

What does an IUD do?

An IUD, or Intrauterine Device, is a contraceptive method that prevents pregnancy by either releasing hormones or by using copper. It offers long-term, highly effective birth control when properly inserted.

How does an IUD work as a contraceptive?

An IUD works as a contraceptive through hormonal or non-hormonal mechanisms. Hormonal IUDs release synthetic Progestin, thickening cervical mucus, inhibiting ovulation, and altering the endometrial lining. Non-hormonal copper IUDs impair sperm motility and interfere with fertilization. 

How does an IUD work to stop sperm?

An IUD works to stop sperm by thickening cervical mucus and creating a barrier. Additionally, in the case of copper IUDs, copper ions released by the device are toxic to sperm, impairing their motility and ability to reach and fertilize an egg.

When will an IUD start working?

An IUD starts working immediately upon insertion for ParaGard, Mirena, and Liletta. For Kyleena and Skyla, immediate protection occurs if inserted within 7 days of menstruation; otherwise, protection begins after 7 days, requiring alternative contraception during the interim to prevent pregnancy.

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