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CACNA1A Gene Mutation Analysis (CAG Repeat Number)

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

This test checks for a specific genetic variation in the CACNA1A gene, which involves a repeating sequence (CAG) that may affect how your body functions. It is often used in research or specialized genetic testing.

Quick summary

This test helps identify genetic patterns linked to certain neurological conditions.

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

Key facts at a glance

LOINC
49650-5
Short code
CACNA1A-A2
Synonyms
CACNA1A allele 2 CAG Rpt EntNum Bld/T
Category
chemistry
Sample
whole-blood
Container
EDTA (purple-top) tube for whole blood; sterile container for tissue
Units
N/A
Ref low
4
Ref high
18
Critical range
— – 20 N/A
Fasting
false
Population
adult
Sex
all
Age range
≥ 0 years
Method
molgen
CPT
81243
SNOMED
444908005
Specimen volume
5-10 mL whole blood; 5-10 mg tissue
Stability
Whole blood: ambient 7 days, refrigerated 14 days, frozen at -20°C for long-term storage. DNA extracted from blood stable for years at -20°C. Tissue: refrigerate at 4°C for 24 hours, frozen at -80°C for long-term storage.
Hemolysis max
0
Lipemia max
0
Icterus max
0
TAT
168–720 hours
Order
routine

Why This Test Might Be Ordered

Your healthcare provider may recommend this test if you have symptoms of a neurological disorder, a family history of related conditions, or if you are part of a research study investigating genetic variations in this gene. It is sometimes used in prenatal or carrier screening contexts.

What to Expect During the Test

The test typically involves collecting a blood sample from a vein in your arm. The sample is then sent to a laboratory for genetic analysis. Results are usually available within a few weeks, depending on the laboratory’s process.

Understanding the Results

The test measures the number of CAG repeats in the CACNA1A gene. Variations in this repeat sequence can be associated with genetic disorders like epilepsy, migraines, or other neurological conditions. Your healthcare provider will explain the meaning of your results in the context of your medical history and symptoms.

Common Conditions Linked to This Gene

Abnormalities in the CACNA1A gene have been linked to conditions such as epilepsy, particularly those affecting the brain’s electrical activity, and certain types of migraines. Genetic testing helps determine if you carry a variant that may increase your risk or contribute to symptoms.

Reference range

Normal CACNA1A CAG repeat range: 4-18 repeats in allele 2. Repeats above 20 are associated with spinocerebellar ataxia type 6 (SCA6). Intermediate alleles (19-20 repeats) require clinical correlation.N/A

Specimen: whole-blood

No fasting or special preparation required. Genetic counseling is recommended before and after testing. Informed consent may be required per institutional policy. Patient should be informed of implications for family members.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

This test is primarily used for research purposes or in specialized clinical settings where genetic counseling and detailed analysis of the CAG repeat number are important. It may also be part of a broader genetic evaluation if you have a family history of neurological disorders. Results can guide treatment decisions or inform reproductive planning if applicable.

Short name

CACNA1A Mutation Screening

Frequently asked questions

What does a high or low CAG repeat number mean?
A high or low number of CAG repeats compared to standard ranges may indicate a genetic variation that could be associated with neurological conditions. However, the exact clinical significance depends on the specific number and your overall health. Your healthcare provider will interpret the results with you.
Does this test require fasting?
No fasting is required for this genetic blood test. You can eat and drink normally before the sample is collected.
How long will it take to get my results?
Results typically take 2 to 4 weeks or longer, depending on the laboratory’s workflow and whether additional testing is needed. Your healthcare provider will contact you once the results are ready.
  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