Getting tested for PCOS and endometriosis involves different paths. PCOS can typically be diagnosed through blood work and an ultrasound in a single office visit, while endometriosis is harder to pin down and may require imaging, a trial of treatment, or even surgery for a definitive answer. Here’s what to expect for each condition and how to prepare.
How PCOS Is Diagnosed
PCOS diagnosis follows what’s known as the Rotterdam criteria: you need to meet at least two of three conditions. Those are irregular or absent ovulation (which usually shows up as irregular or missing periods), higher-than-normal androgen levels (male-type hormones), and polycystic-appearing ovaries on ultrasound. Importantly, your doctor also needs to rule out other explanations for your symptoms, like thyroid disorders or adrenal conditions, before confirming PCOS.
There’s no single test that confirms it. Instead, your doctor pieces together your symptom history, blood results, and sometimes an ultrasound to build the picture.
Blood Tests for PCOS
The core blood panel checks your levels of LH, FSH, estradiol, testosterone, and prolactin. If your doctor suspects PCOS, they’ll typically want this blood draw done on days 1 through 5 of your menstrual cycle, because testosterone levels can be misleadingly high later in the cycle. If your periods have stopped entirely, the blood can be drawn at any time.
Most people with PCOS have total testosterone levels under 150 ng/dL. If your level comes back at 200 ng/dL or higher, that’s a red flag for something else entirely, like an ovarian or adrenal tumor, and warrants further investigation. Your doctor may also look at the ratio between LH and FSH. A ratio of 2:1 or higher suggests PCOS, though it’s not definitive on its own.
Depending on your weight and family history, your doctor may also check fasting glucose, insulin levels, and a diabetes marker called HbA1c. Insulin resistance is common with PCOS and affects treatment decisions, so this step matters even though it’s not part of the formal diagnostic criteria.
Ultrasound for PCOS
The ultrasound looks for a specific pattern: 12 or more small follicles (2 to 9 mm in diameter) in a single ovary, or an ovary with a volume of 10 mL or greater. Only one ovary needs to meet these thresholds for the “polycystic ovary” criterion to be satisfied. A transvaginal ultrasound provides the clearest view, though an abdominal ultrasound can be used if needed.
It’s worth knowing that polycystic-looking ovaries are common in young women who don’t have PCOS. That’s why the ultrasound alone doesn’t equal a diagnosis. It has to be paired with at least one of the other two criteria: irregular cycles or elevated androgens.
How Endometriosis Is Diagnosed
Endometriosis is significantly harder to diagnose. The tissue grows outside the uterus in places it shouldn’t be, like the ovaries, bowel, bladder, or the lining of the pelvis. The only way to confirm it with 100% certainty is surgery, specifically a laparoscopy where a surgeon can see and biopsy the tissue directly. That said, most doctors don’t jump straight to surgery. They work through less invasive steps first.
Imaging: What It Can and Can’t Find
A transvaginal ultrasound is usually the first imaging test ordered when endometriosis is suspected. It’s good at spotting endometriosis cysts on the ovaries (called endometriomas) and is the recommended first-line tool for deeper tissue involvement. For deep endometriosis affecting the bowel, bladder, or the space between the vagina and rectum, MRI tends to be more sensitive. MRI picks up lesions in those locations with sensitivity ranging from about 77% to 95%, compared to 9% to 86% for ultrasound in the rectovaginal area, for instance.
The major limitation is superficial endometriosis. Small, shallow lesions that sit less than 5 mm beneath the surface of the pelvic lining don’t reliably show up on either ultrasound or MRI. These are best found during surgery. So a normal ultrasound or MRI does not rule out endometriosis, particularly early-stage disease. The accuracy of both imaging methods also depends heavily on the experience of the person performing or reading the scan, so getting imaging done at a center familiar with endometriosis makes a real difference.
Laparoscopy: The Definitive Test
If imaging is inconclusive but symptoms are strong, or if your doctor needs a definitive answer, they may recommend a diagnostic laparoscopy. This is a minimally invasive surgery done under general anesthesia. The surgeon makes a small incision near your navel and inserts a thin camera to visually inspect the pelvic organs. If they find suspicious tissue, they take a biopsy sample, which is examined under a microscope to confirm whether it’s endometriosis.
Laparoscopy also provides information about the location, extent, and size of any growths. If endometriosis is found, the surgeon assigns a stage from I (minimal) through IV (severe) based on a point system that accounts for lesion size, depth, and adhesions across the ovaries, peritoneum, and fallopian tubes. A single finding of complete cul-de-sac obliteration, where scar tissue seals off the space behind the uterus, automatically classifies as severe disease. Many surgeons will treat visible endometriosis during the same procedure rather than requiring a second surgery.
Recovery from a diagnostic laparoscopy is relatively quick for most people, typically a few days to a week of downtime, though deep excision surgery takes longer to heal from.
Noninvasive Blood Tests on the Horizon
Researchers at Yale School of Medicine have identified small RNA molecules in the blood, called microRNAs, that can accurately detect endometriosis without surgery. In a trial of 100 patients, these biomarkers correctly identified the disease through a standard blood draw. The team is now studying whether the same approach works in younger patients with earlier-stage disease. This test is not yet commercially available and still needs further validation, but it represents a meaningful step toward replacing surgery as the diagnostic standard.
When You Suspect Both Conditions
PCOS and endometriosis can coexist, and their symptoms overlap more than many people realize. Pelvic pain, heavy periods, and difficulty getting pregnant can show up in both. The diagnostic workups don’t interfere with each other, so your doctor can pursue both simultaneously. Blood work for PCOS hormones can be drawn at the same visit where other conditions are being ruled out, and a transvaginal ultrasound can evaluate for both polycystic ovary morphology and endometriomas at the same time.
Other conditions that can mimic or overlap with these include thyroid dysfunction, uterine fibroids, pelvic adhesions from prior infections or surgeries, and benign ovarian cysts. Your doctor will likely screen for thyroid issues as part of the initial workup, since an underactive or overactive thyroid can cause irregular periods and fatigue that look a lot like PCOS.
Preparing for Your Appointment
The most useful thing you can bring to your appointment is a detailed symptom log. Track at least two to three months of the following before your visit:
- Period dates and flow: when your period starts and stops, how heavy it is, and any spotting between cycles
- Pain patterns: where you feel pain (lower abdomen, back, during bowel movements, during sex), when it happens relative to your cycle, and how severe it is on a 1-to-10 scale
- Other symptoms: acne, new facial or body hair growth, hair thinning on your scalp, unexplained weight changes, fatigue, bloating
- Bathroom habits: changes in bowel movements or urination around your period, which can point toward endometriosis involving the bowel or bladder
If your doctor orders hormone blood work, ask whether you should schedule the draw for early in your cycle (days 1 through 5). Fasting may be required if glucose and insulin testing are included. If you’re on hormonal birth control, discuss with your doctor whether you need to stop it before testing, since it can mask both PCOS hormone patterns and endometriosis symptoms.