What most people are told:
When emergency contraception comes up, the conversation usually focuses on pills like Levonorgestrel (Plan B) or Ulipristal acetate.
These can be helpful tools.
But they are not the most effective option available.
The option that rarely gets discussed: the IUD
A copper IUD as well as the Mirena IUD (Hormonal) can be used as emergency contraception when inserted within 5 days after unprotected sex.
It is:
The most effective form of emergency contraception available
Effective regardless of body weight
Not dependent on timing relative to ovulation in the same way pills are
How it works (and why it’s so effective):
Unlike pills that aim to delay ovulation, an IUD works locally inside the uterus:
Copper creates a spermicidal environment
Mirena reduces the endometrial lining
Prevents sperm from reaching and fertilizing an egg
May also prevent implantation
This means it works even if ovulation has already occurred, which is a key limitation of oral options.
Effectiveness comparison:
Method | Timing window | Effectiveness |
IUD | Up to 5–7 days | >99% |
Ulipristal acetate | Up to 5 days | ~85–95% |
Levonorgestrel | Best within 72 hours | ~75–89% |
The difference is clinically meaningful.
An added benefit: long-term contraception
One of the most important distinctions:
Emergency contraception pills → one-time use
IUD → ongoing contraception for 5–10 years
So in a single visit, you’re addressing:
Immediate pregnancy risk
Future contraception needs
Who this is a strong option for:
An IUD for emergency contraception can be particularly useful if someone:
Wants the most effective option available
Is unsure where they are in their cycle
Has had multiple episodes of unprotected sex in the same cycle
Prefers a non-hormonal method (copper)
Wants to leave with reliable long-term contraception already in place
When it may not be the best fit:
This option requires a clinical procedure, so it may not be ideal if:
There is active pelvic infection
There are certain uterine abnormalities
The person prefers to avoid an in-office procedure
It’s also important to note:
Periods may become heavier and more crampy, especially in the first few months
Practical considerations:
Needs to be inserted by a trained clinician
Timing matters: sooner is better, but there is a wider window than pills
Same-day access depends on clinic availability
If you are within a week of unprotected sex and want the most reliable form of emergency contraception, a copper or hormonal IUD is worth discussing.
It is not just an alternative. It is the most effective option we have.
