Kyleena is the IUD most widely recognized for having blue strings, and it is the answer most people are looking for when they search this question. Liletta, another hormonal IUD, also has blue strings. The color is not decorative; it serves a clinical purpose, helping providers and users distinguish one device from another during exams and string checks. But string color is only one small piece of a larger picture that matters more than most people realize once an IUD is in place.
A Quick Guide to IUD String Colors
Five IUDs have been commonly available in the United States in recent years, and their string colors break down like this:
- Kyleena: Blue strings. This is the smaller-frame hormonal IUD releasing 19.5 mg of levonorgestrel over five years.
- Liletta: Blue strings. A hormonal IUD releasing 52 mg of levonorgestrel, approved for up to eight years of use.
- Mirena: Brown or dark tan strings. Also a 52 mg levonorgestrel device, approved for up to eight years.
- Paragard: White strings. The only copper (non-hormonal) IUD available in the U.S., approved for up to ten years.
- Skyla: Brown strings. A smaller hormonal IUD that has been discontinued in the U.S. market but may still be in place for some users.
If you are trying to figure out which IUD you have based on what you can feel or see at the cervix, string color is one of the quickest identifiers. Blue strings narrow it down to Kyleena or Liletta. Brown strings point to Mirena or Skyla. White strings mean Paragard. Of course, if you are uncertain, your medical records or a call to your provider’s office will confirm it.
Why Blue and Not Some Other Color
The choice of blue is practical, not aesthetic. IUD strings hang through the cervical canal and rest just inside or slightly outside the cervical opening. When a provider examines you with a speculum, those strings need to be visible against the pink-red backdrop of cervical and vaginal tissue. White strings can be hard to spot against pale tissue. Brown strings blend in with discharge or blood. Blue provides high contrast against almost every shade of mucosal tissue, making it faster and easier for clinicians to confirm the IUD is in place.
The blue color also gives manufacturers a way to brand-differentiate their devices in a crowded field. When Kyleena launched, it entered a market where Mirena was already dominant and had brown strings. Giving Kyleena blue strings created an instant visual distinction. Liletta followed a similar logic. For providers who insert multiple IUD types daily, the ability to glance at string color and immediately know the device type saves time and prevents documentation errors.
What IUD Strings Are Actually Made Of
IUD strings are not thread in the way you might picture sewing thread. They are thin strands of medical-grade polyethylene, a type of plastic used across a wide range of implantable medical devices because of its durability, flexibility, and low reactivity with body tissue. The strings are semi-rigid when first inserted and soften somewhat over time as body heat and moisture condition the material.
The blue color comes from a pigment mixed into the polyethylene during manufacturing. Phthalocyanine blue is one of the pigments commonly used for coloring medical-grade polymers. It is an organic pigment known for its stability and resistance to fading, even in warm, moist environments. Research on phthalocyanine blue pigments in polymer matrices has shown that even trace concentrations of the pigment can affect the physical properties of the plastic, including its crystallization behavior, though at the tiny concentrations used in IUD strings, the effect on string performance is negligible.1Advanced Materials Research. Effects of Phthalocyanine Blue and Ultramarine Blue Pigments on Nucleation of Polypropylene The brown color in Mirena’s strings comes from iron oxide pigment, while Paragard’s white strings are essentially unpigmented polyethylene.
You might wonder whether the pigment could leach into your body. These pigments are chosen specifically because they are locked into the polymer structure and do not migrate in meaningful amounts. Phthalocyanine blue is used in food packaging, surgical instruments, and many other applications where material contact with the body or food supply demands regulatory clearance. The strings undergo biocompatibility testing as part of the overall IUD’s approval process.
How to Check Your Own Strings
Regardless of color, the monthly string check is one of the most useful habits you can build after getting an IUD. The point is not to see the strings (you usually cannot without a mirror and speculum) but to feel them. After washing your hands, insert a finger into the vagina until you reach the cervix, which feels like a firm, rounded nub, somewhat like the tip of your nose. You should feel one or two thin, slightly stiff filaments coming through the opening. They may curl around the cervix or point downward.
The best time to check is after your period, if you still have one, because the cervix sits slightly lower and the strings are easier to reach. What you are checking for is consistency: the strings feel the same from month to month. You should not feel the hard plastic of the IUD body itself. If you do, that could indicate partial expulsion, and you should contact your provider.
Some people find string checks stressful or uncomfortable, and skipping a month here and there is not a crisis. The check is a reassurance tool, not a medical requirement. Your IUD is working even if you do not check the strings. But if you notice a sudden change, like strings that seem much longer, much shorter, or completely absent, that is worth a call to your clinic.
When You Cannot Find Your Strings
Missing strings are one of the most common reasons people end up anxiously searching the internet about their IUD. In most cases, the explanation is benign. The strings may have curled up into the cervical canal, where your finger simply cannot reach them. The cervix changes position throughout the menstrual cycle, sometimes sitting higher in the vagina and making the strings harder to feel. Occasionally, strings retract fully into the uterine cavity, especially after the IUD has been in place for a while.
However, missing strings can also signal that the IUD has shifted position or been expelled without your noticing. Expulsion happens in a small percentage of users, most often in the first few months after insertion. This is why providers take missing strings seriously and typically schedule an office visit to investigate.
The standard first step is an ultrasound to look for the IUD inside the uterus. If the IUD appears to be properly positioned on ultrasound, the retracted strings are considered a cosmetic nuisance, not a medical problem. Some providers will use a thin instrument to try to retrieve the strings from the cervical canal. If the IUD cannot be seen on ultrasound, the situation gets more complicated. Researchers have noted that ultrasound alone can sometimes fail to locate a levonorgestrel IUD because these devices are smaller and less echogenic than copper IUDs, and have recommended pairing ultrasound with an X-ray to avoid misdiagnosing a migrated IUD as an expelled one.2PubMed Central. Levonorgestrel intrauterine device with absence of threads: don’t take expulsion for granted! A case series of possible errors in ultrasound evaluation, in case of “lost IUDs” In other words, if your provider says the IUD appears to have fallen out based on ultrasound alone, it may be worth asking whether an X-ray could confirm that before you go through a reinsertion you may not need.
Does String Color Affect How They Feel
People sometimes wonder whether the blue strings on Kyleena or Liletta feel different from the brown strings on Mirena or the white strings on Paragard. In terms of the pigment itself, no. The color additive does not change the texture, stiffness, or thickness of the string in any way you could detect by touch. What does differ between devices is the number and gauge of the strings.
All current IUDs have two strings attached to the base of the T-shaped frame. These strings are trimmed after insertion, usually to about two to three centimeters of length protruding from the cervical os. A provider may trim them shorter if a partner reports feeling them during intercourse. Shorter strings tend to poke more because they do not have enough length to soften and curl. Ironically, the fix for a partner feeling the strings is sometimes to leave them longer, not shorter, so they drape along the vaginal walls rather than sticking straight out.
Paragard strings are sometimes described as feeling slightly stiffer than the strings on hormonal IUDs, though this varies by individual experience and may be influenced by how long the device has been in place. Over time, all IUD strings tend to soften and become less noticeable. If your strings are consistently bothersome to you or a partner months after insertion, bring it up at a follow-up appointment. Your provider can re-trim the strings or discuss whether a different length might help.
String Color and IUD Identification After Removal
There is one slightly unusual context in which string color matters a lot: when an IUD is found outside of a clinical record. Emergency departments occasionally encounter patients who do not know which IUD they have, perhaps because it was placed years ago at a different clinic, or records were lost. In that scenario, string color becomes the fastest identification tool. Blue strings immediately tell the clinician it is a levonorgestrel device, either Kyleena or Liletta, which is relevant for assessing contraceptive coverage, managing side effects, or planning removal. White strings identify Paragard, which matters because copper IUDs can sometimes cause heavier periods and cramping, and their removal technique can differ if the device has been in place for many years.
If you ever need emergency care related to your IUD and you do not have your records handy, telling the provider the color of your strings gives them useful information immediately. It is also worth keeping a note in your phone or wallet with your IUD type, insertion date, and expiration date, because string color alone cannot distinguish between Kyleena and Liletta.
Why Providers Care About String Visibility More Than Patients Think
From a user’s perspective, the strings are a minor afterthought once the insertion cramps fade. From a clinician’s standpoint, string visibility is a surprisingly important clinical marker. Visible strings at a routine exam confirm several things at once: the IUD has not been expelled, the device has not perforated the uterine wall, and the IUD is likely in proper fundal position (sitting at the top of the uterus where it belongs). All of this is communicated by two thin threads hanging through the cervix.
When strings are not visible, the provider has to order imaging, which costs time and money, delays reassurance, and in rare cases leads to unnecessary interventions. High-contrast string colors reduce the chance of a false alarm. A provider using a speculum in a room with imperfect lighting can spot blue strings more quickly and confidently than faint white ones. This is a mundane-sounding advantage, but across millions of IUD check-ups per year, it adds up.
Strings After Special Insertion Situations
The way an IUD is inserted can affect whether you can feel the strings afterward. In a standard office insertion through the cervix, the strings are trimmed and left visible at the cervical os. But IUDs are also placed in some non-standard scenarios, and string behavior can differ.
When an IUD is placed immediately after a cesarean delivery (known as intracesarean insertion), the device is placed directly through the uterine incision rather than through the cervix. In this case, the strings are tucked into the uterine cavity and may not descend through the cervix for weeks or even months. Some people who had an IUD placed during a C-section never feel the strings at all, because the strings coil inside the uterus rather than passing through the cervical canal. This does not mean the IUD has failed or migrated; it is a known consequence of the insertion route. Providers typically rely on imaging rather than string checks to confirm proper placement after intracesarean insertion.
Postpartum insertion through the cervix, whether immediately after vaginal delivery or several weeks later, also has a higher rate of string retraction compared to interval insertion (placement that is not connected to a recent pregnancy). The uterus is larger and softer after delivery, and it takes time to involute back to its pre-pregnancy size. As the uterus shrinks, the strings may change position, sometimes descending to become palpable when they were not before, or retracting further. If you had an IUD placed in a postpartum setting and cannot feel the strings, it is especially worth mentioning this context to your provider so they calibrate their concern appropriately.
When Partners Notice the Color
It occasionally surprises people to learn that a sexual partner can sometimes see or feel IUD strings. During penetrative intercourse, a partner may feel the tips of the strings against the head of the penis or a finger. In rare situations, a partner examining the cervix with a finger during intimacy might notice the string color. Blue strings get commented on more often, simply because the color is unexpected and noticeable, while white or brown strings tend to blend in and go unmentioned.
If a partner reports being poked or scratched by the strings, the issue is string length and stiffness, not the device itself. As mentioned earlier, very short strings are the most common culprit. Strings that are left longer tend to soften and tuck against the vaginal walls. Your provider can re-trim them, though this should be done carefully because strings that are trimmed too short can become difficult to locate for removal later. Some couples find that the sensation diminishes within a few months as the strings soften with time, without any adjustment needed.