One of the questions I most often receive when deciding on contraception is "Isn't there a method I don't have to keep up with every day?" In the clinic, there are many who often forget oral pills or who want stable contraception for several years after childbirth. The option that comes up at such times is Implanon, a subdermal implant contraceptive device in which a thin rod is placed on the inner arm. Today, I will calmly organize how this device works, how long the effect lasts, and what to attend to before and after insertion, based on professional society recommendations.
What kind of device is Implanon?
Implanon is a thin rod-shaped contraceptive device containing a hormone, used by placing it just under the skin of the inner arm. Its length is slightly shorter than a matchstick and its thickness is about 2 mm, so after insertion, feeling the arm reveals a firm rod shape.
The rod contains 68 mg of etonogestrel. Etonogestrel is a synthetic luteinizing hormone of the progestin class, a component that acts similarly to the progesterone secreted in our body. Along with this are an EVA component that maintains the rod's shape and barium sulfate that helps confirm its position by X-ray.
Hormone is released a little at a time, steadily, from the inserted rod, spreading into the tissue and acting throughout the body along the bloodstream. Its characteristic of being a "progestin-only preparation" without estrogen is why it is also considered for those for whom estrogen use is a burden. The UK's Faculty of Sexual and Reproductive Healthcare (FSRH) classifies Implanon, together with the intrauterine device, as long-acting reversible contraception (LARC).
By what principle does it prevent pregnancy?
Implanon's contraceptive principle is not one thing but is achieved by several actions overlapping. The core is ovulation suppression.
When etonogestrel acts steadily, the ovulation signal sent from the brain to the ovaries is suppressed, so the egg is not released. The FSRH (2021, revised 2023) and the American College of Obstetricians and Gynecologists (ACOG, 2017) explain Implanon's main action as ovulation suppression, to which two supplementary actions are added.
- It thickens the cervical mucus, making it hard for sperm to enter the uterus.
- It keeps the endometrium thin, creating an environment unfavorable for implantation.
Because it blocks at several stages this way, the societies classify Implanon and the intrauterine device as "the most effective among reversible contraceptive methods." Unlike a pill that must be taken daily, there is little for the user to attend to, so a low possibility of failure arising from human forgetfulness is reported as a major advantage.
In the clinic, I often receive the question, "Once it's in, can I feel safe right from that day?" The answer is, "It depends on the timing of insertion." If inserted within 5 days of the start of menstruation, no additional contraception is needed, but if inserted outside that period, it is recommended to also use additional contraception such as condoms for the first few days to be safe.
If you want to broadly compare various contraceptive options, reading guidance summarizing what types of contraception there are together will help.
How long does the effect last?
Implanon is a long-acting method in which a single insertion provides contraception for several years.
It is known that the blood hormone concentration reaches a level sufficient to suppress ovulation from a relatively early point after insertion. Thereafter, while the hormone from the rod gradually decreases, it maintains the concentration needed for contraception for a certain period. The approved duration of use differs by country and time, having long been used as 3 years, and recently changes that further extend the duration of use based on clinical data are also being reported. Since the exact replacement timing differs depending on the product in use and your own condition, it is good to confirm it through a medical visit.
| Category | Implanon (subdermal implant) | Oral pill | Intrauterine device |
|---|---|---|---|
| Method of use | One insertion in the arm | Daily intake | Inserted in the uterus |
| Duration | Several years | Must be kept up daily | Several years |
| User burden | Low | Must attend to daily | Low |
| Estrogen | None | Included depending on product | Differs by product |
If you are curious about the intrauterine device, a similar long-term contraceptive, you can check the differences in an article on Mirena's principles and side effects. If it is hard to decide which method suits you, I recommend getting a consultation suited to your condition at the pregnancy and contraception clinic.
Advantages and disadvantages of Implanon
Implanon's greatest advantages are the convenience of not having to keep up with it daily and its high contraceptive effect.
The advantages can be summarized as follows.
- Once inserted, it is maintained for several years, so there is little worry about forgetting daily intake.
- It contains no estrogen, so it can be considered even in situations where estrogen use is difficult.
- When removed, the hormonal effect disappears relatively quickly, so fertility is reported to return at a relatively early time when planning pregnancy.
That said, the limits are also clear. The most common disadvantage is a change in menstrual pattern. According to ACOG (2017), irregular bleeding, spotting, or amenorrhea can appear in Implanon users, and this is explained as related to the endometrium thinning while estrogen concentration is kept low. Besides this, headache, breast pain, and mood changes are also reported, and there may be individual variation in these reactions. Also, Implanon does not protect against sexually transmitted infections, so in situations where infection prevention is needed, it is good to use condoms together.
If you wonder to what extent bleeding change is normal, an article on how to view bleeding after insertion is also helpful. If you are worried about your own bleeding pattern, please feel free to ask through a consultation on bleeding changes.
Insertion and removal, and precautions to attend to
For Implanon, accurately knowing the timing of insertion and the management after removal is the key to safe use.
Insertion is done by placing the rod under the skin of the inner arm after local anesthesia. As explained earlier, if placed within 5 days of the start of menstruation, no additional contraception is needed, but if outside that period, it is recommended to use additional contraception such as condoms together for the first few days.
There is one important point at removal too. When the rod is removed, the blood hormone concentration drops quickly, and in clinical experience, a contraceptive effect is hard to expect right from immediately after removal. Therefore, if you do not want to become pregnant, you must start another contraceptive method such as condoms right from the very day of removal. Since there is individual variation in the response to hormones, if the insertion position is hard to feel or there are symptoms different from usual, it is safe to confirm through a medical visit.
Implanon is not the most suitable method for everyone. The more suitable contraceptive method may differ depending on medications you are taking or existing conditions, so when you are unsure about choosing a contraceptive method, rather than deciding alone, I recommend finding the method that suits you through a consultation.
Organizing the frequently asked questions
Let me organize a few questions repeatedly heard in the clinic regarding Implanon.
First is the question "Does inserting it hurt a lot?" Since it is done after local anesthesia, pain during the procedure is reported to be not severe, but there is individual variation in how it is felt. Second is the worry "What if contraception fails?" Implanon is classified as a highly effective method, but no contraceptive method guarantees perfection, so knowing in advance the timing for taking emergency contraception, which is to respond without delay, will help. Third, to the question "How does it differ from other methods?" I also recommend guidance broadly covering contraception as a whole.
For contraception, whether it suits your lifestyle and health condition matters as much as its effectiveness. Rather than vaguely choosing one method, I hope you decide after examining your own situation together.
If you want to know whether Implanon is the right method for you, please feel free to ask by clicking a contraception method consultation.
Today I organized the principle, duration, advantages and disadvantages of Implanon, the subdermal implant long-term contraceptive device inserted on the inner arm, and the points to attend to during insertion and removal. Whatever the contraceptive method, it must suit your body condition and lifestyle to be used with peace of mind for a long time. If you have questions, we will look into them together through a medical visit.
Written by Lee Dong-hee, Director · OB-GYN specialist · See physician profile
First published December 4, 2023 · Last reviewed May 30, 2026
References: FSRH Guideline Progestogen-only Implants (2021, revised 2023), ACOG Practice Bulletin No. 186 Long-Acting Reversible Contraception (2017)
This article is intended to provide general health information and does not replace individual diagnosis or treatment. If you have symptoms, please consult through a medical visit.