What are the differences between a hormonal IUD (intrauterine device), such as Mirena (levonorgestrel), and a copper IUD, like ParaGard, for contraception?

Hormonal IUD vs Copper IUD: Key Differences

Both the hormonal (levonorgestrel) IUD and copper IUD are highly effective contraceptives with failure rates less than 1%, but they differ fundamentally in mechanism, bleeding patterns, duration of use, and therapeutic benefits—making the levonorgestrel IUD superior for women with heavy or painful periods, while the copper IUD is ideal for those wanting hormone-free contraception or the longest duration of protection. 1, 2

Efficacy and Duration

Both IUD types provide exceptional contraceptive protection:

• Copper IUD (ParaGard): Approved for 10 years, with data supporting effectiveness up to 12 years 1
• Levonorgestrel IUD (Mirena 52mg): Approved for 5 years, but remains effective for up to 7 years 1, 2
• Levonorgestrel IUD (Liletta 52mg): Approved for 3 years 1
• Levonorgestrel IUD (Skyla 13.5mg): Approved for 3 years 1, 2
• Both achieve pregnancy rates of 0.0-0.2 per 100 woman-years, comparable to surgical sterilization 3, 4

Mechanism of Action

The devices work through different mechanisms:

• Copper IUD: Creates a toxic environment for sperm through copper ions; works immediately upon insertion 1
• Levonorgestrel IUD: Thickens cervical mucus and inhibits sperm motility; releases 20 mcg levonorgestrel per 24 hours locally in the uterine cavity 2, 5
• Both prevent fertilization before implantation occurs 2, 5

Menstrual Bleeding Patterns: The Critical Difference

This is where the two devices diverge most dramatically:

Copper IUD

• Increases menstrual bleeding and cramping, particularly in the first months after insertion 1, 5
• Women continue regular menstrual cycles 1
• Increased bleeding may persist even with long-term use 5, 6

Levonorgestrel IUD

• Dramatically reduces menstrual blood loss by 90% from baseline within the first year 3
• Many women develop oligomenorrhea or complete amenorrhea 1, 2, 7
• Irregular spotting is common during the first 2-3 months but typically resolves 3, 6
• Significantly improves dysmenorrhea (painful periods) 1, 3, 6

Therapeutic Benefits Beyond Contraception

The levonorgestrel IUD offers substantial non-contraceptive health benefits:

• First-line treatment for menorrhagia (heavy menstrual bleeding), reducing blood loss by 90% 2, 3
• Effective therapy for dysmenorrhea, endometriosis, and adenomyosis 2, 8
• Increases body iron stores by reducing menstrual blood loss 3
• Protective effect against pelvic inflammatory disease compared to copper IUD (0.5% vs 2.0% cumulative 36-month rate, p<0.013) 7, 3
• Reduces risk of ectopic pregnancy (0.02 per 100 woman-years) 3

The copper IUD provides no therapeutic benefits beyond contraception 1

Safety Profile

Both devices are safe for nulliparous adolescents and do not cause tubal infertility 1, 2

Infection Risk

• Small risk of pelvic infection exists only in the first 20-21 days after insertion for both types 1, 2
• Levonorgestrel IUD demonstrates significantly lower rates of pelvic inflammatory disease compared to copper IUD 7, 3
• Both can be inserted in asymptomatic high-risk patients with same-day STI screening 1, 2

Side Effects

Levonorgestrel IUD specific:

• Headaches, nausea, breast tenderness 5
• Hair loss, depression, decreased libido 5
• Delayed ovarian follicular atresia (functional cysts) 6
• Skin and hair conditions 6
• Amenorrhea (which many women find desirable) 1, 2

Copper IUD specific:

• Increased menstrual bleeding and cramping (primary side effect) 1, 5
• Higher rates of dysmenorrhea 6

When to Start and Backup Contraception

Copper IUD

• Can be inserted anytime in the menstrual cycle 1
• No backup contraception needed 1
• Most effective emergency contraception method (failure rate <1%) 1

Levonorgestrel IUD

• Can be inserted anytime, but if >7 days after menses started, requires 7 days of backup contraception (abstinence or barrier methods) 1
• Prescribing information advises insertion during first 7 days of menses 5

Special Populations

Adolescents and Nulliparous Women

• Both devices are appropriate and safe 1, 2
• Neither causes tubal infertility 1, 2
• Levonorgestrel IUD particularly useful for adolescents needing menstrual suppression when estrogen is contraindicated 2

Postpartum

• Both can be inserted ≥4 weeks postpartum 8
• Immediate postpartum insertion possible but has higher expulsion rates 5
• Levonorgestrel IUD prescribing information recommends waiting 6 weeks postpartum 5

Breastfeeding

• Both are acceptable for breastfeeding women 5
• Levonorgestrel IUD is progestin-only with no estrogen-related concerns 2, 8

Clinical Decision Algorithm

Choose Levonorgestrel IUD when:

• Heavy menstrual bleeding (menorrhagia) present 2, 3
• Painful periods (dysmenorrhea) present 1, 3
• Desire for lighter periods or amenorrhea 1, 2
• History of endometriosis or adenomyosis 2, 8
• Anemia or low iron stores 3
• Estrogen contraindicated but hormones acceptable 2, 8

Choose Copper IUD when:

• Desire for completely hormone-free contraception 1
• Longest duration of protection desired (10-12 years) 1
• Need for immediate contraceptive effect without backup 1
• Emergency contraception needed 1
• Unacceptable to have irregular bleeding or amenorrhea 1
• Concerns about hormonal side effects (mood, libido, headaches) 5

Common Pitfalls to Avoid

• Do not assume nulliparous women or adolescents cannot use IUDs—both devices are safe and appropriate for these populations 1, 2
• Do not remove IUD if pelvic inflammatory disease develops—treat the infection and reassess in 2-3 days 1
• Do not delay IUD insertion for STI screening results in asymptomatic high-risk patients—screen same day and treat subsequently if needed 1, 2
• Do not counsel patients that irregular bleeding with levonorgestrel IUD is permanent—it typically resolves after 2-3 months 3, 6
• Do not forget to counsel about 7-day backup contraception when inserting levonorgestrel IUD >7 days after menses 1