Contraceptive Injection: Understand How the Method Works and Ask Questions

Contraceptive injection consists of injectable hormones, which are applied monthly or every three months in the gluteal region, for those who want to avoid pregnancy.

This method is ideal for those who forget to take the pill daily or cannot use oral contraceptives on medical advice. Also, it has a lower cost.

But not all are advantages. Contraceptive injection may cause some adverse reactions and may make pregnancy more difficult even after stopping use.


Obstetrician and gynecologist Rodrigo da Rosa Filho, a specialist in human reproduction, better explains the positives and negatives, the right way to use injectable contraception and clarifies other doubts about this method.

How does it work and who is it for?

Contraceptive injection should be taken only if professionally advised. This indication takes into account various factors such as health issues, intolerance to certain types of hormones, habits and even lifestyle. Between the monthly injection, the oral pill or birth control patch, the basic difference is more in the form of application. And practicality changes, as forgetting is a very common problem. But is the effectiveness the same ?, says the doctor.

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Application should always be done at the pharmacy as it is an intramuscular application. According to the doctor, it is little painful. "It only hurts if it's misapplied," he says.

Monthly x quarterly injectable contraceptive

The gynecologist also clarifies that there are two types of injectable methods. One is applied monthly with synthetic combined hormones (estradiol and progesterone derivatives) that have the same characteristics as the pill and the contraceptive patch.

It is widely used by teenagers who often forget the pill, also has fewer side effects, especially gastrointestinal, such as nausea. • This injection is given every 30 days, always on the same day of the month. The first should be applied on the first day of menstruation. And the cycle is normal, without any change ?, he says.


The other has quarterly application. Its composition is based on progestogen only (similar to natural progesterone), without estrogen. “It has the advantage of having no contraindications. It is even widely used in the postpartum period, because it does not interfere with breastfeeding. But has the disadvantage of increasing fluid retention over time ?, explains Rodrigo.

Another different feature of quarterly injection is that women do not menstruate. "It is very indicated in cases that we do not want the patient to menstruate, such as endometriosis," he says.

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Possible side effects

The monthly injection, because of the combined hormones, has the same risks as the birth control pill or patch, such as thrombosis, heart attack, stroke, liver problems. This does not change regardless of the route of administration, ie whether it is oral or injectable.

Therefore, it is a contraindicated method for those who are predisposed to any of these problems and also for smokers. Women who are breastfeeding cannot use the method either, as there is interference.

The quarterly injection does not have any of these contraindications, since it has no estrogen in its composition.

More questions answered

Before opting for an injectable contraceptive method, it is important to know more details about it, its advantages, disadvantages and risks. Obstetrician and gynecologist Rodrigo da Rosa Filho answers some common questions.

Injectable birth control fattening?

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Yes. Injectables have a higher amount of hormone, which increases fluid retention. That's why any woman who starts injections is likely to gain more weight, but it also varies greatly from organism to organism.

Will my menstrual cycle change with the injection?

It depends. In the monthly injection the person continues to menstruate monthly. In the quarterly there is no menstruation.

Injection dispenses with the use of condoms?

To avoid sexually transmitted diseases, no. The condom is still needed.But for contraception the injection is very effective.

Read also: Know the hormones used in birth control pills

I started taking the injection this month, am I already protected?

Yes. Efficacy is from the first time you take the injection.

When can I get pregnant after stopping injections?

The monthly does not interfere with fertility. If you stop taking it, you will be back to the normal cycle the following month and have chances of pregnancy in the next cycle. In the quarterly, after discontinuation of use, it may take six months to a year for the woman to ovulate and menstruate again. Therefore it is only indicated in very specific cases.

I forgot to take it on the right day, is there a problem taking late?

If you forget, you have up to three days to take again without risk. In the quarterly is even quieter, with a more flexible term.

If I want to stop menstruation, is there any way?

In the case of injection, there is no way to stop menstruation, because it is not indicated to apply more than one per month. If you do not want to menstruate, this is not a good method.

How long can I use the injectable contraceptive?

There is no deadline for monthly injection use. If you are feeling well without contraindications, you can always use. It can start in adolescence and go to the premenopausal phase. But the quarterly can be applied for a maximum of three years, because it can induce osteoporosis.

How much does each injection cost?

The monthly costs around 30 reais, a much lower value compared to other methods. According to the doctor, many women opt for injection because of the cost. The quarterly comes for about 40 reais, is even cheaper.

It is important to note that only a doctor can evaluate each case and prescribe the best contraceptive method to avoid health damage.

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