Injection
One quick jab every three months, done at the clinic - no fuss, no daily thinking, and nothing anyone can see.
Gets an A+ in pregnancy prevention.
The cheat Sheet
Common brand names
Depo-Provera and Depo-Ralovera
Preventing pregnancy
99.8% effective with perfect use, 96% effective with typical use.
Starting on this method
You’ll need a prescription from your GP or gynaecologist to start the injection. If you get it within the first 5 days of your period, you’re protected from pregnancy straight away. If not, you might need to use backup contraception for the first 7 days, just to be safe.
Lasts for
One shot lasts 12 weeks (about 3 months) before your next injection is due.
Hormones
Yes, contains synthetic hormone - progestogen
STIs
No protection against STIs
Periods
Your period may change, some people have lighter, more regular bleeding, while others may experience spotting or heavier flow, especially at first.
Acne/skin
Can improve and/or worsen your acne/skin
Mood/emotions
May help or affect your mood, depending on how your body reacts to the hormones.
Pregnancy after removal
You can get pregnant after the injection wears off, but it might take 18 months or so for your fertility to return to normal. For some, it happens sooner.
Visibility
Completely invisible, unless you choose to share.
Financial investment
Available by prescription in Australia, and may be partly covered by Medicare.
The hormonal injection contains a progestogen-only hormone. It doesn’t contain estrogen like the combined pill, just straight-up progestogen power (specifically a hormone called depot medroxyprogesterone acetate). It’s given as a shot, usually in the arm or butt, and slowly releases the synthetic hormone into your bloodstream over 8–13 weeks, depending on the type.
Once it’s in your system, it gets to work like a long-acting undercover agent, silently but effectively guarding the gates against pregnancy.
Here’s how it works:
1. Thickens cervical mucus
Imagine the cervix is the entrance to a fancy garden party, and sperm are uninvited guests. Normally, the gate (cervical mucus) is open with a smooth path. But under the influence of progestogen, that path turns into a pit of quicksand; thick, dense, and nearly impossible to cross. Most sperm get stuck before they even make it to the gate. Poor things, the party is popping off!
2. Thins the uterine lining
The uterus usually fluffs up its lining like a cozy bed, getting ready to welcome a fertilised egg. The hormone in the injection strips the bed and take away the welcome mat, making it much harder for anything to settle in and stay. Because guess what, this hotel has no vacancies!
3. Stops ovulation
Think of your ovaries like a vending machine that releases one egg (snack) each month. The hormones in the injection switch off the machine, so no egg gets released. No egg means nothing for sperm to fertilise; therefore no pregnancy!
- Those whose bodies aren't fans of synthetic oestrogen, this one leaves it out entirely.
- Practically made for anyone who dreads their period - cramps, endless pad changing, the whole painful shebang and wishes it would just nick off.
- If you like your contraception like your underwear: doing its job, totally unseen.
- It won’t protect against STIs, so if that’s on your radar, consider adding condoms to the mix.
- You’ll need to pop by the doctor every 3 months for your top-up; it’s not a DIY gig.
- When you stop, your natural cycle might take a little nap before returning. Patience required. This isn’t a good option if you want to get pregnant soon.
The not-so-fun stuff
Common side effects
Let’s be honest. No contraceptive method is perfect. And when it comes to hormonal contraception, side effects can feel like a bit of a lucky dip. What one person barely notices, another might really struggle with. Everyone responds differently - physically, emotionally, mentally and every response is valid.
We want you to have the full picture so you can make a decision that works for your body, not just what looks good on paper.
So here it is: the good, the meh, and the stuff worth keeping an eye on.
Most people adjust after 2-3 months of using the injection, but here are some side effects that tend to show up early on:
- Changes to your period (often lighter or no periods at all, but some spotting is common)
- Headaches
- Bloating
- Weight changes or increased appetite (about 1 in 5 users will experience weight gain)
- Mood changes
- Acne and/or skin changes
- Breast tenderness
- Decreased sex drive
We love clinical stats. But we also love hearing from people who’ve actually used it. These insights are pulled from real reviews on The Lowdown:
- Emotional ups and downs or mood swings
- Weight gain
- Skin changes
- Decreased sex drive
- Stopped periods
- Vaginal dryness
- Tender breasts
- Lower back pain
- Period-like cramps
Less Common But important to know
Before you hit the “nope” button, hang tight. We're not here to freak you out, just to make sure you’ve got all the info you need to make an informed choice.
The injection lowers estrogen levels, which can gradually reduce bone strength over time. Because of this, it’s recommended to use the injection for no more than 2 years unless no other method works for you. Bone density often recovers after stopping, especially in the spine, but recovery can depend on how long you’ve used it.
There’s a small increase in breast cancer risk, especially for people under 35, but this returns to baseline after stopping. Unlike the pill, the injection doesn’t protect against cancers like ovarian or bowel cancer. There may be a small increase in cervical cancer risk with long-term use, but research is still ongoing. Overall, the risk is low, but if you have a family history of cancer, talk it through with your doctor.
Hormonal contraception is not a one-size-fits-all so when it comes to how your mood will be affected by synthetic hormones, it's a bit of a trial and error. If you’ve ever felt like your mental health is connected to your hormones, you’re not imagining it.
Some people using the implant report mood swings, low mood, or anxiety. Others feel no change at all, or even more emotionally steady than before. The research is mixed, but a growing number of studies suggest that people with a history of things like depression, anxiety, or PMDD may be more sensitive to hormonal shifts.
If you notice changes in your mood after getting the injection, whether that’s a subtle shift or something more significant, it’s worth tracking and bringing up with a healthcare provider. You are the expert on your body, and you deserve care that takes mental health seriously.
You’re not overreacting. You’re paying attention. And that matters. Go you good human!
If the injection fails (which is unlikely) and you do become pregnant, there's a slightly higher chance that the pregnancy could be ectopic, meaning it implants outside the uterus, usually in a fallopian tube. It’s rare, but important to know the signs: severe one-sided pain, unusual bleeding, or feeling dizzy or faint. If anything feels off, check in with your doctor, just to be safe.
Your hormones explained
Localised vs non-localised hormones
Methods like hormonal IUDs and the vaginal ring
- These are designed to release hormones directly to the uterus or cervix, with the goal of staying “local.”
- Ovulation may or may not be suppressed, depending on the method and you as a human!
- They’re often described as “low impact” but there’s some grey area to that.
Methods like the combined pill, injection and implant
- Hormones are delivered into your bloodstream and circulate throughout your entire body.
- That means they can influence your brain, breasts, skin, bones, libido, mood, appetite…pretty much everything.
- Ovulation is usually fully suppressed.
- There’s a strong potential for both physical and psychological effects, because these hormones touch every system.
Even local methods like the hormonal IUD aren’t truly local. A portion of those hormones still enter your bloodstream. And once they’re in? They’re catching an Uber straight to your central nervous system, aka your brain, which is basically a hormone sponge.
Your brain has estrogen and progesterone receptors scattered throughout:
- Amygdala (emotion)
- Hippocampus (memory)
- Prefrontal cortex (decision-making, motivation)
- Hypothalamus (hormone regulation)
- Brainstem (autonomic nervous system)
That’s a lot of big words but in other words, your brain is not just along for the ride, it’s driving the car.
If you’ve ever said:
- “I don’t feel like myself on birth control.”
- “The IUD was meant to be low-impact, but I still felt off.”
- “It helped my skin but wrecked my libido.”
- “I feel calm, but numb.”
You’re not imagining it. You’re experiencing the full-body, full-mind reality of synthetic hormones - even from methods that are “local”.
No matter how the hormones are absorbed, through your uterus, your skin, your gut, or a tiny implant in your arm, synthetic hormones affect all of you. That doesn’t make them bad. It just makes them pretty powerful.
Knowing how they work gives you the info you need to figure out what’s right for you!
Troubleshooting the Injection
These things happen - we understand! It depends on how late you are.
Less than 2 weeks late - you’re probably still protected, but it's best to check with your doctor or pharmacist to be sure.
More than 2 weeks late - you may not be protected. You’ll need to use backup contraception (like condoms) for 7 days after your next shot.
Unfortunately, the injection can’t be done at home; it needs to be given by a healthcare professional. The good news is that you do have options:
- Try a local sexual health clinic or community health centre, some offer walk-in or low-cost appointments to get the injection done.
- In some remote regions, pharmacists or nurses can administer the injection.
- If access is still tricky, consider a self-managed method like the pill or patch for now and switch later when in-person care is easier to reach.
Yep, totally normal. Over half of users stop bleeding altogether after 12-24 months. It’s safe, it doesn’t mean anything’s wrong, and your uterus isn’t “backing up.” But if no periods feel weird for you, you're allowed to feel that way too.
Nope, you can just not get your next shot. The hormone will slowly leave your system over time. Just keep in mind that it might take 9-12 months (or more) for your cycle and fertility to return to your baseline.
Where this info comes from
This page was created using guidance from trusted Australian and international health organisations, clinical guidelines, and peer-reviewed research. These sources support the medical accuracy, accessibility, and lived experience approach behind this content.
- BetterHealth Channel - Contraception Injections
- Family Planning NSW - Contraceptive Injection
- Healthdirect Australia - Contraceptive injection
- Sexual Health Victoria - Depo Provera
- SHINE SA – Injectable Contraception
- MSI Australia – Contraceptive Injection
- Body Talk – Contraceptive Injection
- NPS Medicine Wise - Depo-Provera
- Alvergne, A., & Lummaa, V. (2010). Does the contraceptive pill alter mate choice in humans? Trends in Ecology & Evolution, 25(3), 171–179. DOI: 10.1016/j.tree.2009.08.003.
- Brønnick, M. K., Ottowitz, W. E., Pfeifer, G., & Pletzer, B. (2020). Systematic review of neuroimaging studies on hormonal contraceptives. Frontiers in Psychology, 11, 1560. DOI: 10.3389/fpsyg.2020.556577
- Lauring, J. R., Lehman, E. B., Deimling, T. A., Legro, R. S., & Chuang, C. H. (2016). Combined hormonal contraception use in reproductive-age women with contraindications to estrogen use. American Journal of Obstetrics and Gynecology, 215(3), 330.e1–330.e7. https://doi.org/10.1016/j.ajog.2016.03.047
- Pletzer, B., & Kerschbaum, H. H. (2014). 50 years of hormonal contraception—Time to find out what it does to our brain. Frontiers in Neuroscience, 8, 256. DOI: 10.3389/fnins.2014.00256
- Skovlund, C. W., Morch, L. S., Skovlund, C. W., et al. (2016). Association of hormonal contraception with depression. JAMA Psychiatry, 73(11), 1154–1162. https://jamanetwork.com/journals/jamapsychiatry/fullarticle/2552796
- World Health Organization, International Agency for Research on Cancer. (2007). Combined estrogen–progestogen contraceptives and combined estrogen–progestogen menopausal therapy (IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Vol. 91). https://publications.iarc.fr/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Combined-Estrogen--Progestogen-Contraceptives-And-Combined-Estrogen-Progestogen-Menopausal-Therapy-2007
- Otten, C. (2021). The sex ed you never had. Allen & Unwin.
- Hill, S. E. (2019). This is your brain on birth control: The surprising science of women, hormones, and the law of unintended consequences. Avery.
