Compare

Copper IUD vs Diaphragm

A side-by-side comparison of two birth control methods — efficacy, cost, how they work, and who shouldn't use them.

Last verified October 11, 2026Updated October 11, 2026

Side-by-side comparison

Copper IUD A small copper device placed in the uterus that works for up to 10 years and is over 99% effective.
Diaphragm A reusable silicone dome that covers the cervix to block sperm, used with spermicide each time you have sex.

Method	Copper IUD A small copper device placed in the uterus that works for up to 10 years and is over 99% effective.	Diaphragm A reusable silicone dome that covers the cervix to block sperm, used with spermicide each time you have sex.
Efficacy	Copper IUD 99.2% typical use Most effective: over 99 out of 100 people successfully prevent pregnancy per year.	Diaphragm 83% typical use Least effective: under 90 out of 100 people successfully prevent pregnancy per year.
Cost	Copper IUD $0–$1,167 Insurance: Usually	Diaphragm $0–$250 Insurance: Usually
Duration	Copper IUD Up to 10 years	Diaphragm Reusable for up to 2 years (replace sooner if damaged)
Reversibility	Copper IUD Reversible	Diaphragm Reversible
STI protection	Copper IUD No	Diaphragm No
How it works	Copper IUD Releases copper into the uterus, which interferes with sperm movement and fertilization and may prevent implantation.	Diaphragm A reusable silicone dome covers the cervix to block sperm from reaching an egg. Used with spermicide for added effectiveness.
Prescription	Copper IUD Required In-Person Procedure	Diaphragm Required Hybrid (Fitting or Ship)
Side effects	Copper IUD Heavier or longer periods (especially first few months) Increased cramping Spotting between periods Small risk of uterine perforation at insertion	Diaphragm Increased risk of urinary tract infection Vaginal irritation from spermicide Toxic shock syndrome risk (rare)
Who shouldn't use this	Copper IUD Active pelvic infection or PID (FDA label) Uterine abnormality that distorts the uterine cavity (FDA label) Wilson's disease (copper metabolism disorder) (FDA label) Known copper allergy (FDA label) Current pregnancy (FDA label)	Diaphragm Uterine or cervical anomaly preventing fit Sensitivity to silicone or spermicide Inability to insert or remove reliably History of toxic shock syndrome High risk of HIV exposure (because of the spermicide)

Key differences

With typical use, 0.8 in 100 people using Copper IUD get pregnant in a year, vs 17 in 100 with Diaphragm (most effective vs least effective). How long it lasts: Copper IUD, up to 10 years; Diaphragm, reusable for up to 2 years (replace sooner if damaged). Copper IUD: costs $0–$1,167. Diaphragm: costs $0–$250.