Test ID: S-122 | Sample Type: Saliva | Technology: LC-MS/MS | Results Time: 3–5 Working Days After Laboratory Receives Sample | Laboratory: ZRT Laboratory – CLIA Certified | Hormone Specialist Doctor Interpretation: Included | Suitable For: Adults and Children
What Does This Test Measure?
Saliva — Cortisol Awakening Response + Full Adrenal Profile (LC-MS/MS): Cortisol Upon Waking, Cortisol +30 Minutes, Cortisol +60 Minutes, Midday Cortisol, Evening Cortisol, Night Cortisol, DHEAS.
7 markers — the most detailed adrenal assessment available at home, capturing the full morning CAR window, the complete daily cortisol rhythm, and the primary adrenal testosterone precursor in a single saliva kit.
Related Symptoms
Waking exhausted despite adequate sleep, anxiety or restlessness immediately on waking, persistent fatigue or low energy that does not improve with rest, insomnia or night waking, low libido or erectile dysfunction, loss of muscle mass or poor gym recovery, unexplained abdominal fat gain, anxiety, irritability, low mood, brain fog, chronic stress or burnout, symptoms of low testosterone with inconclusive standard blood results, or suspected adrenal fatigue or HPA axis dysfunction.
Did You Know?
The Cortisol Awakening Response — the 50% cortisol surge that occurs within 30 minutes of waking — is the most clinically informative single window into HPA axis function available from non-invasive testing. For men, the shape of this morning curve directly determines: how much testosterone suppression via pregnenolone steal occurs during the day; how effectively deep sleep-based testosterone synthesis proceeds at night; and how resilient the androgenic system is to physical and psychological stress. A blunted CAR (flat morning curve) is the definitive marker of adrenal burnout and chronic overtraining. An exaggerated CAR signals acute HPA hyperreactivity with immediate testosterone suppression. Neither pattern is detectable from a single morning time point — the three-sample CAR window is required to distinguish them, and both are missed entirely by standard blood panels.
Who Should Consider This Test?
- Waking exhausted despite adequate sleep
- Anxiety, restlessness, or a sense of pressure immediately upon waking
- Persistent fatigue or low energy that does not improve with rest
- Insomnia, night waking, or inability to switch off at bedtime
- Low libido or reduced sexual interest
- Erectile dysfunction or reduced sexual performance
- Loss of muscle mass or poor recovery after training
- Unexplained abdominal fat gain despite exercise
- Anxiety, irritability, or low mood
- Brain fog, poor focus, or reduced motivation
- Symptoms of low testosterone with normal or inconclusive standard blood results
- Chronic stress, overtraining, or burnout
- Currently on TRT and wanting a complete adrenal picture
- Suspected adrenal fatigue or HPA axis dysfunction
- Men wanting the most detailed cortisol assessment available before considering clinical intervention
Why This Test Is Particularly Important for Men
- The three-sample CAR window (waking, +30 min, +60 min) is the only way to distinguish a blunted CAR from an exaggerated CAR — clinically opposite patterns that cause similar symptoms but require completely different interventions; a single morning reading cannot make this distinction
- The morning cortisol surge directly determines testosterone suppression magnitude via pregnenolone steal — men with an exaggerated CAR lose the highest proportion of testosterone precursor to cortisol during the hours when androgenic drive for the day is set
- DHEAS is the primary adrenal testosterone precursor in men — combined with the CAR pattern, the DHEAS-to-cortisol relationship provides the most complete assessment of adrenal-driven androgenic status available from a single at-home test
- Elevated evening and night cortisol directly suppress the deep sleep phases responsible for the majority of daily testosterone production — the full 6-point profile identifies whether this nocturnal suppression is present and at which time point it begins
- For men on TRT, the CAR test identifies whether adrenal dysfunction is the reason TRT is underperforming — cortisol dysregulation and DHEAS deficiency are the most common causes of residual androgenic deficiency symptoms despite adequate testosterone dosing
Not Sure Which Test Is Right for You?
Email us at info@hormonelab.co.uk with your gender, age, symptoms, medications, and any current treatments. We will forward your enquiry to our doctors and respond within 24 hours.
Collection Protocol
Six saliva samples collected across the day:
- Sample 1: Within 5 minutes of waking — before getting out of bed, ideally 6–8am
- Sample 2: 30 minutes after waking
- Sample 3: 60 minutes after waking
- Sample 4: Midday
- Sample 5: Evening
- Sample 6: Night (before sleep)
Full collection instructions are included in the kit. The three morning samples must be collected at exact intervals — do not eat, drink, or brush your teeth before completing all three.
How It Works
- Order your kit — delivered directly to your door
- Collect six saliva samples across the day following the detailed instructions provided
- Post your samples to ZRT Laboratory using the return instructions provided
- Receive your full report by email within 3–5 working days
What You Receive
- All six cortisol readings and DHEAS with male-specific reference ranges
- Full diurnal cortisol curve graph including the complete CAR window
- Written interpretation by a Hormone Specialist PhD Doctor including CAR pattern classification, cortisol–testosterone impact assessment, and DHEAS adrenal reserve evaluation
- Personalised next-step recommendations
- Laboratory fee included — no hidden charges
Why We Use ZRT Laboratory
All testing is performed by ZRT Laboratory — a globally recognised, CLIA-certified diagnostic laboratory founded in 1998 by Dr. David Zava, PhD. ZRT has performed over 11 million tests and is trusted by healthcare professionals in 96+ countries.
- Pioneers of at-home dried blood spot (DBS) and saliva hormone testing
- Advanced LC-MS/MS technology for clinical-grade accuracy
- Qualified for the CDC Hormone Standardization (HoSt) Program
- Personalised reference ranges based on age and sex
Through our partnership with ZRT Laboratory, Hormone Lab UK delivers internationally recognised, research-backed hormone testing to people across the UK and Europe — from the comfort of home.
Frequently Asked Questions
What does this test measure?
Cortisol at six time points (waking, +30 min, +60 min, midday, evening, night) and DHEAS — 7 markers providing the most detailed adrenal and HPA axis assessment available from a single at-home saliva test.
Why is the CAR particularly important for men?
The morning cortisol surge directly determines testosterone suppression via pregnenolone steal during the day and the quality of sleep-based testosterone synthesis at night. The three-sample CAR window is the only method that can distinguish a blunted from an exaggerated CAR — two opposite patterns with different clinical implications that a single morning reading cannot differentiate.
Can I use this test if I am on TRT?
Yes. This test is particularly valuable for men on TRT wanting to understand whether adrenal dysfunction — including CAR dysregulation and DHEAS deficiency — is undermining the effectiveness of testosterone therapy.
Do I need to fast before collecting?
No fasting is required. Follow the timing instructions carefully — particularly for the three morning samples, which must be collected at exact intervals and before eating, drinking, or brushing your teeth.
Does the price include the laboratory fee?
Yes. The full laboratory analysis fee is included. There are no additional charges. You are only responsible for posting your samples to the laboratory.
How long is the kit valid for?
The kit must be used within 12 months of the purchase date.
