Androgen Receptor Sensitivity (CAG Repeat Genetic Test)
Ever wonder why two men with identical testosterone levels can feel so different? The answer lies in your genes. Step into the future of precision hormone optimization with Marek Health's exclusive Androgen Receptor Sensitivity (AR-CAG) Test, designed to reveal exactly how sensitive your body is to testosterone. Whether you're exploring hormone therapy or simply curious about your hormonal health, this test provides insight to fine-tune your hormone optimization strategy.
Test details
- Androgen Receptor Gene Analysis for CAG Repeat Expansion Length
Genetic analysis performed via combination of repeat-primed analysis PCR and fluorescent fragment-length assay.
Why consider this panel?
The AR-CAG repeat test evaluates the genetic sensitivity of your androgen receptors (AR). Shorter AR-CAG repeats are associated with higher androgen receptor sensitivity, meaning stronger testosterone effects at lower hormone levels. Longer repeats correlate with reduced sensitivity, which may contribute to symptoms of androgen deficiency despite normal lab values.
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How it works
1. Purchase this test
This is an at-home test that ships directly to you. No lab visit is required - just place your order and we’ll take care of the rest.
2. Collect your at-home sample
After you order, we’ll ship your collection kit straight to your door. Most kits arrive within one week.
3. Receive your lab results
Use the prepaid shipping label to return your kit. You’ll receive your results by email within 2–3 weeks.
Lab panel details
Sample type: Saliva
HSA/FSA: Accepted
Results: Emailed to you
Preparation: No fasting required
Meets treatment requirements: No
If you have any questions, you are always welcome to contact us. We'll get back to you as soon as possible, within 24 hours on weekdays.
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What is the androgen receptor and why does it matter?
Androgens & The AR Connection
Androgens like testosterone, DHT, and DHEA drive muscle, strength, libido, and vitality—but only if they bind effectively to the androgen receptor (AR).
Think of the AR as a lock and testosterone as the key. When unlocked properly, it activates vital genetic signals.
Your AR sensitivity shapes how well your body responds to hormones and treatments like TRT, fertility protocols, or finasteride—making it essential for optimizing results and avoiding guesswork.
Why do identical hormone levels or medication doses produce different results?
This phenomenon is called interindividual variability, the reason two people with identical testosterone levels, TRT dosages, or even the same hair loss medication (like finasteride) can feel or respond completely differently.
These differences largely come down to your genetics, specifically variations in the androgen receptor (AR) gene that determine how effectively your body responds to testosterone and other androgens.
Think of standard bloodwork as a fuel gauge. It shows how much hormone ("fuel") you have but not how efficiently your body uses that fuel. A half-tank of gas won’t take a sports car nearly as far as a compact sedan. Similarly, individuals with identical hormone levels can experience dramatically different outcomes as a result of differences in their receptor sensitivity.
What exactly is AR-CAG repeat length, and why does it matter for androgen sensitivity?
The AR-CAG is a specific genetic sequence within your androgen receptor (AR) gene, consisting of repeating units known as CAG repeats. The length of this sequence directly influences how sensitive your androgen receptor is to testosterone and other androgens.
In other words, shorter CAG repeats typically allow androgens to trigger a stronger response at the receptor, while longer repeats blunt this effect.
Measuring your CAG repeat length provides much-needed context, helping you better understand your body's unique biological response to androgens in a more nuanced way.
While other factors do impact how the body responds to testosterone and other androgens, AR-CAG repeat length is the best known genetic determinant of Androgen-Receptor sensitivity.
What does the research say about AR-CAG length?
Two decades of research demonstrate that your AR-CAG repeat length can profoundly influence diagnosis, treatment decisions, and outcomes related to hormone health. Key insights include:
Research-Backed Insights
Over 20 years of research show that AR-CAG repeat length significantly impacts diagnosis, treatment, and outcomes in hormone health.
Improved Testosterone Range Identification
Combining AR-CAG data with blood tests refines Low-T diagnosis and helps define your ideal testosterone range.
Personalized TRT Dosing
Shorter repeats = higher sensitivity, requiring lower doses. Longer repeats may need higher doses for results.
Variable Response to Hair Loss Medications
Finasteride tends to work better in men with shorter AR-CAG repeats than those with longer ones.
Identifying Symptoms Despite “Normal” T Levels
Men with longer AR-CAG repeats may still show Low-T symptoms even if labs appear normal, underscoring the need for personalized reference ranges.
Metabolic Impact of TRT
AR-CAG length can influence insulin sensitivity and body composition changes during testosterone therapy.
Hematological Monitoring
Shorter repeats may lead to greater increases in markers like hematocrit and hemoglobin, making individualized TRT monitoring essential.
Fertility Optimization
AR-CAG length may affect how well fertility treatments work by influencing intra-testicular testosterone and sperm production.
Why have I never heard of this test?
It often takes 17+ years for cutting-edge science to enter standard medical practice—especially with insurance pushback. Marek Health is closing that gap by making advanced diagnostic tools like AR-CAG testing accessible and actionable.
While this test has existed for diagnosing rare diseases (like Kennedy’s), traditional versions only flag “normal” vs. “abnormal,” missing crucial variations. Marek is the first and only provider offering a detailed AR-CAG repeat length test built for people seeking personalized hormone and health insights.
Note: While Marek Diagnostics offers self-service labs for independent testing, the Marek Health team includes coaches and board-certified medical practitioners capable of helping you interpret high-leverage biomarkers like AR-CAG repeat length within the context of comprehensive blood testing and personalized health strategies.
Lab work FAQs
Please read our FAQs page to find out more.
How quickly will my lab results arrive?
Your lab results will typically arrive within two weeks, though processing time may vary based on the size and complexity of your panel. Rest assured, once your results are ready, they will be securely delivered to your email. No waiting rooms. No chasing paperwork. Just precision diagnostics at your fingertips.
Does Marek Diagnostics accept insurance?
Marek Diagnostics is a cash-pay service. Our platform offers direct access to comprehensive testing without the limitations, denials, or delays imposed by insurance companies. If traditional insurance covered the kind of proactive, high-quality lab work we offer, Marek Diagnostics wouldn’t need to exist.
However, many clients successfully use their HSA/FSA to cover their testing costs. Marek Diagnostics is partnered with TrueMed for convenient deployment of HSA/FSA funds at checkout.
My panel Meets Treatment Requirements — what does that mean?
Marek Diagnostics is an extension of Marek Health, the leading health optimization platform designed to turn your results into informed action.
If your panel Meets Treatment Requirements, you’re eligible to enroll into Guided Optimization, an exclusive program that connects you with:
- Detailed, expert led lab analysis
- A consultation with a Marek Health coach and board-certified medical provider
- A precision health optimization plan
- Access to high-quality treatment options
If you’re unsure what to do with your results, Marek Health is the bridge between lab results and achieving your goals.
Do I need to pay a separate fee at the lab to get my blood drawn?
No additional payment is required at the lab. Our expert-built panels include the venipuncture and if you’re building a custom panel or testing biomarkers individually, a $5 venipuncture fee will be automatically added at checkout.
