Hormonal IUD (Mirena/Kyleena) Missed-Dose Protocol: What to Do and When to Worry

Why "Missed Dose" Means Something Different With a Hormonal IUD

There are no tablets to forget. Mirena and Kyleena deliver levonorgestrel (LNG) continuously from a T-shaped polypropylene frame directly into your uterine cavity. The contraceptive effect is almost entirely local: the hormone thickens cervical mucus within hours of insertion, suppresses endometrial receptivity, and partially suppresses ovulation in some cycles, without requiring any action from you.

Levonorgestrel IUDs work through local, not systemic, mechanisms, which is why they carry a fraction of the hormonal exposure of a daily pill. Mirena releases approximately 20 mcg/day at insertion, falling to roughly 10 mcg/day by 5 years, and averaging about 6 mcg/day over its FDA-approved 8-year lifespan. Kyleena releases approximately 17.5 mcg/day initially, declining to 7.4 mcg/day by 5 years over its FDA-approved 5-year lifespan.

So what actually counts as a "missed dose" with an IUD? Three scenarios:

1. Device expiration (using the IUD beyond its approved duration)
2. Partial expulsion (device partially displaced from the uterine cavity)
3. Complete expulsion (device fully expelled, offering zero protection)

Each requires a different clinical response. The table below maps the scenario to the urgency.

| Scenario | Contraceptive Coverage | Action Required | Urgency | |---|---|---|---| | Approaching approved expiry | Still effective until expiry date | Schedule replacement | Routine | | Past approved expiry | Unknown, likely declining | Replace immediately | High | | Partial expulsion detected | Reduced or none | Remove and replace | Same-day call | | Complete expulsion | None | Emergency contraception if indicated + new device | Urgent | | Placement check overdue (no string check in 1+ year) | Likely intact but unconfirmed | Ultrasound confirmation | Non-urgent |

How to Know If Your Device Is Still in Place

The String Check

You should feel for your IUD strings once a month, ideally just after your period ends when the cervix is easiest to reach. Insert one or two clean fingers into the vagina until you touch the cervix. The strings should feel like thin fishing line protruding a centimeter or two from the cervical os. If you feel the hard plastic frame of the device itself, the IUD has shifted. If you feel nothing, you may have simply lost track of strings that curled up, or the device may have been expelled.

What Warrants a Same-Day Call

Call your clinician the same day if you:

• Feel the plastic frame with your fingers at the cervix
• Feel severe cramping or pelvic pain that appeared suddenly
• Cannot find strings that were consistently palpable before
• Suspect you passed the device during a heavy period (some women report seeing it in the toilet or on a pad)

Confirming Position With Ultrasound

Transvaginal ultrasound is the gold standard for confirming IUD location when strings are missing or ambiguous. ACOG Practice Bulletin guidance on IUDs supports ultrasound when clinical string assessment is inconclusive. The device appears as two bright echogenic lines on sagittal view when correctly positioned in the uterine fundus.

Scenario 1: Your Device Is Approaching or Past Its Expiration Date

Mirena (52 mg) Timing

The FDA extended Mirena's approved duration from 5 years to 7 years in 2022 and then to 8 years in 2023, based on data showing sustained LNG levels and contraceptive efficacy through year 8. If you had Mirena placed before 2022 and were told "5 years," your device may still be within its approved window. Confirm the original insertion date with your provider.

If you are past 8 years from insertion date, your device is expired. You are not covered.

Kyleena (19.5 mg) Timing

Kyleena is approved for 5 years only. There is no extended-duration approval. Replace at or before month 60 from insertion.

What Happens If You Wait Too Long

No randomized trial has measured pregnancy rates in women continuing LNG-IUDs beyond approved durations, so any estimate of "how much does efficacy drop after year 8" is extrapolated from pharmacokinetic modeling rather than direct outcome data. This is an honest evidence gap. Levonorgestrel tissue levels in the device at 8 years are measurable but low, and local cervical mucus thickening may persist to some degree past expiry. Still, no regulatory body endorses extended use beyond labeled duration for contraception, and relying on a device past its approval date means accepting an unquantified pregnancy risk.

Replacement Timing: Back-to-Back Insertion

A new IUD can be inserted at the same visit the old one is removed. ACOG and the CDC Medical Eligibility Criteria for Contraceptive Use both support same-day replacement, with no backup contraception required if the new device is placed immediately. If you defer replacement to a later date, you need a backup method (condoms, or consider emergency contraception if you had unprotected sex in the 5 days before the expired device was removed).

Scenario 2: Partial or Complete Expulsion

How Common Is Expulsion?

Expulsion occurs in approximately 3-10% of LNG-IUD users in the first year after insertion, with higher rates in nulliparous women, women with a history of dysmenorrhea, and immediately postpartum insertions. After the first year, expulsion becomes much less common.

Partial Expulsion

If ultrasound shows the device has descended into the cervical canal or lower uterine segment rather than sitting at the fundus, it offers substantially reduced or no contraceptive protection. The device must be removed. At that point, your clinician can discuss same-day replacement or an alternative method.

Complete Expulsion

If the device has been fully expelled and you have had unprotected penis-in-vagina sex within the past 5 days, levonorgestrel 1.5 mg emergency contraception (Plan B or generic) is appropriate, or a copper IUD (Paragard) inserted within 5 days provides both emergency contraception and ongoing coverage. After managing the immediate situation, schedule a new hormonal IUD insertion.

Expulsion Risk by Life Stage

The WomanRx expulsion-risk framework by life stage:

| Life Stage | Expulsion Risk | Notes | |---|---|---| | Reproductive years, parous | Lowest (3-5%) | Optimal uterine cavity dimensions | | Reproductive years, nulliparous | Moderate (5-10%) | Smaller cavity; cramping common post-insertion | | Immediately postpartum (<48 hours) | Higher (up to 24%) | ACOG supports immediate postpartum insertion despite higher expulsion; highly effective if device stays | | Interval postpartum (4-6 weeks) | Similar to reproductive baseline | Standard timing | | Perimenopausal | Lower; irregular bleeding may mask expulsion symptoms | Annual string check recommended |

Scenario 3: You Missed Your Annual String Check

Skipping your self-check or an office string verification for a year or more does not mean the device has moved. Most IUDs that are going to be expelled are expelled in the first 3 months. But if you have never been shown how to check your strings or you have irregular cycles that make monthly tracking difficult, a clinician-performed string check or a point-of-care ultrasound gives you confirmed peace of mind.

The clinical standard is an annual well-woman visit that includes string verification. You don't need an ultrasound every year if the strings are easily palpable.

Sex-Specific Physiology: How the Menstrual Cycle and Hormonal Status Affect the LNG-IUD

During Reproductive Years

Levonorgestrel from the IUD does reach systemic circulation, but at doses far lower than oral progestins. Serum LNG with Mirena averages 150-200 pg/mL, compared to roughly 2,000-6,000 pg/mL with a low-dose oral progestin-only pill. This low systemic level means most women continue to ovulate (especially Kyleena users) and retain roughly normal estradiol cycling, so bone density, libido, and cardiovascular markers are largely unaffected compared to systemic progestin-based methods.

Bleeding changes are the most common hormonal effect you will notice. In the NEJM 2013 trial comparing LNG-IUS to usual care for heavy menstrual bleeding (HMB), women randomized to the LNG-IUD had significantly greater reduction in menstrual blood loss and quality-of-life scores than women receiving standard medical therapy (tranexamic acid or norethisterone). Sixty-four percent of women in the LNG-IUD group reported satisfaction at 2 years, versus 38% in the usual-care group. That trial enrolled 571 women across multiple UK centers and remains the strongest RCT evidence for this indication.

During Perimenopause

This is where the LNG-IUD plays a role well beyond simple contraception. In perimenopausal women, Mirena is commonly prescribed alongside systemic estrogen therapy (ET) to provide endometrial protection, replacing oral or vaginal progestins. The Menopause Society position statement on menopausal hormone therapy acknowledges LNG-IUS as an option for the progestogen component of combined hormone therapy, though it notes this is an off-label use in the United States.

For perimenopausal women who also want contraception, Mirena covers both needs simultaneously. Irregular bleeding in perimenopause can obscure expulsion symptoms, so annual clinical string verification is more important in this group than in younger women.

After Menopause

Once menstrual periods have ceased for 12 consecutive months, contraception is no longer needed. Women using Mirena for endometrial protection within an HRT regimen may continue until the device expires, then reassess whether ongoing ET justifies replacement. There is no clinical need to replace a Mirena purely for endometrial protection in a postmenopausal woman who has stopped estrogen therapy.

Conditions the LNG-IUD Treats or Affects

The LNG-IUD is not only a contraceptive. Understanding its therapeutic overlap helps you evaluate whether expiration or expulsion matters beyond pregnancy prevention.

Heavy menstrual bleeding (HMB): Mirena is FDA-approved for HMB in women who want intrauterine contraception. If your device expires and HMB returns before you can replace it, contact your clinician promptly.

Endometriosis: While not FDA-approved for this indication, evidence supports LNG-IUS for reduction of endometriosis-associated pain, particularly rectovaginal disease. Expulsion or expiration may cause pain recurrence.

PCOS: Women with PCOS may use the LNG-IUD for endometrial protection from unopposed estrogen. An expired device leaves the endometrium unprotected if anovulatory cycles persist.

Fibroids and adenomyosis: LNG-IUS reduces fibroid-related bleeding and is commonly used in adenomyosis management, though expulsion rates may be higher in women with cavity-distorting fibroids.

Perimenopause and HRT: As described above, Mirena replaces oral progestogen in combined HRT regimens.

Pregnancy and Lactation Safety

Pregnancy Category and Risk

The LNG-IUD is contraindicated in confirmed pregnancy. It is not designed to terminate an established pregnancy. If pregnancy occurs with the device in situ (rare: the failure rate is approximately 0.1-0.2% per year with correct placement), there is an increased risk of septic abortion, preterm delivery, and ectopic pregnancy. Any IUD should be removed as early as possible if pregnancy is confirmed, because removal, although not without risk, reduces obstetric complications compared to leaving it in place.

Levonorgestrel at contraceptive IUD doses is not classified as a teratogen in the conventional sense, but animal data and the known progestogenic activity of LNG mean that continuation of a failed IUD in a confirmed intrauterine pregnancy carries real risks. The FDA label states the device should be removed in pregnancy.

If you are trying to conceive, the IUD should be removed. Fertility typically returns within one to three months of removal, with no evidence of prolonged subfertility after LNG-IUD use. ACOG Practice Bulletin 186 confirms prompt return of fertility after IUD removal.

Ectopic Pregnancy Risk

If pregnancy occurs with any IUD in place, approximately half of those pregnancies are ectopic. The absolute risk of ectopic pregnancy with an IUD is lower than without contraception (because the IUD so effectively prevents intrauterine pregnancy), but if a pregnancy does occur, ectopic must be ruled out immediately. If your IUD is expired or expelled and you have a positive pregnancy test, go to an emergency department or your OB's office the same day.

Lactation

LNG-IUS is compatible with breastfeeding. Systemic LNG levels are low enough that transfer to breast milk is minimal, estimated at 0.1% of the maternal dose, and neonatal ingestion has not shown measurable effects in studies up to 12 months postpartum. Both the WHO and ACOG support LNG-IUD insertion at 4-6 weeks postpartum in breastfeeding women. Immediate postpartum insertion (within 48 hours) is also supported and is not associated with reduced breastfeeding rates or duration.

Contraception Requirements

Because the LNG-IUD is itself the contraceptive, there are no additional contraception requirements during use. Backup contraception is recommended for the first 7 days after insertion if the device is placed outside of the first 7 days of the menstrual cycle, per CDC Medical Eligibility Criteria guidelines. At replacement visits, same-day back-to-back insertion eliminates the need for backup.

Who This Is Right For (and Who Should Think Twice)

Strong Candidates

• Women who want highly effective, maintenance-free contraception for 5-8 years
• Women with HMB who want to avoid surgery (Mirena specifically)
• Perimenopausal women on systemic estrogen who need endometrial protection without daily oral progestins
• Postpartum women who want to avoid estrogen-containing methods while breastfeeding
• Women with endometriosis or adenomyosis who benefit from local progestin suppression
• Women with PCOS who need endometrial protection from chronic anovulation

Use With Caution or Discuss Alternatives

• Women with uterine anomalies or cavity-distorting fibroids (higher expulsion risk)
• Women who have had pelvic inflammatory disease within the past 3 months (insertion contraindicated until resolved)
• Women with unexplained abnormal uterine bleeding (evaluate before insertion)
• Women who want to conceive within the next year (choose a shorter-acting method or accept a 1-3 month return-to-fertility gap)
• Women with known or suspected LNG-sensitive breast cancer (insertion is contraindicated per ACOG and CDC MEC Category 4 for current breast cancer)

Step-by-Step: What to Do Right Now

If you are uncertain about your device status, work through this sequence:

1. Find your insertion date. Check your discharge paperwork, pharmacy records, or patient portal. If you cannot find it, call the inserting clinic.
2. Calculate your expiry. Mirena placed before April 2022: check if you are within 8 years. Kyleena: 5 years from insertion.
3. Do a string check. After your next period, feel for the strings at the cervix. Note whether they feel the same length and texture as before.
4. If strings are missing or the frame is palpable: Call your clinician that day for a string check or point-of-care ultrasound.
5. If the device is confirmed expired or expelled: Ask about same-day replacement. Use condoms in the interim. If you have had unprotected sex in the past 5 days, ask about emergency contraception.
6. If everything is confirmed in place and within date: Your next action is to repeat the string check after your next period, and schedule your next replacement appointment before your current expiry date.

As The Menopause Society states: "The levonorgestrel intrauterine system provides effective local endometrial protection and can be considered as the progestogen component of menopausal hormone therapy," underscoring that provider-patient communication about device timing is essential across the reproductive life span, not just in younger women.