Skip to content

Follicular Diameter Measurement (Transvaginal Ultrasound)

Published: August 9, 2026Updated: August 16, 2026

This test measures the size of ovarian follicles, small fluid-filled sacs in the ovaries, using transvaginal ultrasound. It helps assess reproductive health, monitor ovulation, or evaluate conditions like polycystic ovary syndrome (PCOS).

Quick summary

["Ultrasound checks follicle size to guide fertility planning or diagnose ovarian issues."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
11793-7
Short code
Follicle Diam US.meas
Synonyms
Follicle Diam US.meas
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
us-measured
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why This Test Is Done

Doctors may order this test to evaluate ovarian function, track the development of follicles during ovulation, or diagnose conditions affecting the ovaries. It’s often used in fertility treatments, menstrual cycle monitoring, or when symptoms like irregular periods suggest hormonal imbalances.

What to Expect During the Procedure

You’ll lie on your back with a small gel applied to your lower abdomen or vagina. A transducer (probe) is placed externally (abdominal) or inside the vagina to capture images of your ovaries. The procedure is quick, painless, and doesn’t require sedation.

Common Uses and Conditions

This test helps diagnose or monitor conditions such as PCOS, endometriosis, ovarian cysts, or unexplained infertility. It may also be used to confirm ovulation timing or assess ovarian reserve in women undergoing fertility treatments.

Preparation Tips

No special preparation is needed. However, avoid using vaginal creams, tampons, or douching 24 hours before the test to ensure clear images. Wear comfortable clothing and bring your medical records if you have a history of reproductive health issues.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

How long does it take to get results?
Results are typically available within 1–3 business days, depending on your lab or clinic. Your healthcare provider will discuss them during your follow-up visit.
What do my follicle measurements mean?
Measurements alone don’t provide a diagnosis. Your doctor will compare them to your medical history, symptoms, and other test results (like hormone levels) to determine next steps. For example, small follicles might suggest delayed ovulation, while multiple large follicles could indicate PCOS.
Can I eat or drink before the test?
You can eat and drink normally before the test. No fasting is required, and there are no restrictions on fluids or food.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy