Fragile X Syndrome Genetic Test (FMR1)
Uncover the inherited cause of intellectual disability and infertility.
The Fragile X Syndrome Genetic Test (FMR1) is a targeted genetic test for Fragile X syndrome, the most common inherited cause of intellectual disability and a well-recognised cause of autism spectrum disorder and premature ovarian insufficiency. It is intended for individuals with a family history of Fragile X syndrome or related conditions, for those with unexplained developmental delay, intellectual disability or autism, for women experiencing premature ovarian insufficiency or unexplained infertility, and for anyone seeking carrier testing before or during pregnancy. A simple blood sample is taken in clinic and the result is reviewed with your doctor.
What the test examines
- FMR1 gene - the gene responsible for Fragile X syndrome. The test assesses the size and stability of the CGG repeat region within the gene, which determines whether an individual carries a normal, premutation or full mutation allele.
- Fragile X syndrome (FRAX-A/B) - the clinical classification of Fragile X-associated disorders, covering both the full mutation (Fragile X syndrome) and the premutation (Fragile X-associated tremor/ataxia syndrome and Fragile X-associated primary ovarian insufficiency).
Who it is for
- Individuals with a family history of Fragile X syndrome, intellectual disability, autism or premature ovarian insufficiency.
- Children or adults with unexplained developmental delay, learning difficulties or autism spectrum features.
- Women with premature ovarian insufficiency or unexplained infertility.
- Couples considering pregnancy who wish to understand their carrier status.
Why it matters
Identifying an FMR1 expansion provides a clear explanation for developmental, reproductive or neurological concerns and allows informed family planning. Carrier status has important implications for relatives, who may also wish to be tested, and for reproductive options such as prenatal diagnosis or preimplantation genetic testing. Early knowledge supports timely access to developmental, educational and specialist support, and helps clinicians coordinate appropriate surveillance for associated conditions across the lifespan.
FMR1 Gene
- Fragile X syndrome (FRAX-A/B)
- FMR1 CGG repeat expansion status (normal, premutation, full mutation)
No special preparation required.
For blood tests, we recommend drinking plenty of water beforehand to ensure smooth sample collection. If you are taking any regular medication, continue to do so unless advised otherwise by your doctor.
Important Clinical Information:
This test is a screening tool to monitor and support your overall health. It does not replace your GP or consultant.
Always discuss your test results, especially any abnormal results, with your GP, who can interpret them in the context of your medical history and overall health.
- Check whether your test needs fasting: We will tell you when you book, and the FAQ for your test will also say.
- Drink plenty of water beforehand: Being well hydrated makes blood collection easier.
- Wear clothing with sleeves that roll up easily.
- Bring a list of any medicines you take.