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Neurophysiology

Autonomic sweat testing

Tests that measure sweating function - a window on the small autonomic nerves in neuropathy and unexplained sweating disorders.

Key facts

At a glance

  • Why sweat: sweat glands are driven by small autonomic nerve fibres, so measuring sweating tests those fibres directly.

  • The main methods: QSART measures stimulated sweat volume at standard sites; sympathetic skin response and gland-counting methods are alternatives.

  • On the day: mild tingling under small capsules on arm and leg for QSART; sessions take about an hour with no lasting effects.

  • Who needs it: suspected small fibre neuropathy, unexplained absent or excessive sweating, and autonomic disorder workups.

  • Follow-up: results join skin biopsy and cardiovascular autonomic tests in a specialist’s overall assessment.

The full picture

What this test involves, and how to get it

Sweating is run entirely by small autonomic nerve fibres, which makes it a measurable proxy for nerves that standard electrical tests cannot see. The reference method, QSART (quantitative sudomotor axon reflex test), places small capsules on standard sites on the arm and leg; a mild electrical current draws a stimulating chemical into the skin, activating local sweat glands via their nerve supply, and the evoked sweat volume is measured precisely. Reduced output maps damage to the sudomotor small fibres - a core component of small fibre neuropathy and of broader autonomic failure. Simpler alternatives exist where QSART is unavailable: the sympathetic skin response (recordable in ordinary neurophysiology labs), gland-imprint methods, and thermoregulatory sweat testing in a handful of specialist centres.

Sweat testing earns its place in three situations: corroborating small fibre neuropathy alongside skin biopsy and sensory testing; investigating conspicuously absent sweating (anhidrosis) with heat intolerance, which can signal autonomic disease; and characterising autonomic failure syndromes where cardiovascular tests are also abnormal. It is painless beyond transient tingling and takes about an hour. The honest access picture: full QSART provision in the UK is limited to a small number of specialist autonomic units, NHS referral routes are correspondingly narrow, and private access typically flows through consultant autonomic or peripheral nerve specialists who assemble it within a broader workup over a few weeks. For most patients the practical path starts with the specialist consultation, which determines whether sweat testing will genuinely add to biopsy and cardiovascular autonomic results.

A quiet reminder

This guide is for information, not medical advice.

Your own clinician knows your history and can tell you which parts apply to you. Next review of this page: 2027-09-27.

Frequently asked

Common questions about Autonomic sweat testing.

Quick, plain-English answers to what people ask us most.

  • What does the Autonomic sweat testing measure?

    The Autonomic sweat testing measures a specific substance or marker in your blood that helps doctors assess how a particular organ or system in your body is functioning. It's usually interpreted alongside your symptoms, medical history and other results rather than in isolation. Your GP or specialist can explain exactly what your individual result means for you.

  • Why would a doctor request Autonomic sweat testing?

    Autonomic sweat testing is typically requested when a doctor wants to investigate specific symptoms, monitor an existing condition, or check for an underlying imbalance that could explain how you're feeling. It may also be included as part of a broader health check or a more targeted diagnostic panel. Your clinician will explain why it's relevant to your particular situation before requesting it.

  • Do I need to prepare for Autonomic sweat testing?

    Some blood tests require fasting, a specific time of day, or a pause in certain medications, while others need no preparation at all. Because requirements vary and we don't want to guess incorrectly for this specific test, always check the preparation instructions given at booking or ask the clinic directly. Turning up prepared, if preparation is needed, avoids having to rebook and wait again.

  • What happens when I have Autonomic sweat testing?

    Most blood tests involve a short, straightforward appointment where a trained phlebotomist takes a small sample from a vein in your arm. The process usually takes only a few minutes and most people experience nothing more than a brief pinch. You can typically resume normal activities straight away.

  • Does Autonomic sweat testing hurt or carry any risk?

    A standard blood draw causes only brief discomfort at the needle site, with a small risk of bruising or light-headedness afterwards. Serious complications are rare, and staff are trained to make the process as comfortable as possible. Let the phlebotomist know if you've had problems with blood tests before, such as fainting, so they can take extra care.

  • How long does it take to get results?

    Private laboratories generally turn results around within a few working days, though some specialised tests take longer to process. You'll usually be told an expected timeframe when you book, and results are typically reviewed by a doctor before being shared with you. If a result needs urgent attention, the clinic will usually contact you sooner rather than making you wait for a routine follow-up.

  • What does an abnormal Autonomic sweat testing result mean?

    An abnormal result doesn't automatically mean something serious is wrong — levels can be affected by hydration, medication, recent illness, timing of the sample, or normal individual variation. A doctor will look at the size and pattern of any abnormality alongside your symptoms and other results before deciding whether further tests, monitoring, or treatment are needed. It's always worth discussing an abnormal result with a doctor rather than trying to interpret it alone.

  • Can I get Autonomic sweat testing on the NHS, or is it better to go private?

    Many blood tests are available on the NHS, but routine, non-urgent testing can involve a wait for a GP appointment and then for the sample and results. Private testing is typically available within days, often with same-week appointments and results reviewed by a specialist, which can be useful if you want reassurance quickly or your GP hasn't recommended the test. Cost for private testing varies by clinic and whether it's a standalone test or part of a wider panel.

  • How accurate and reliable is Autonomic sweat testing?

    When carried out by an accredited laboratory, this type of blood test is generally considered a reliable way to measure the substance in question. As with any single blood test, results can vary slightly from day to day and are best interpreted in the context of a full clinical picture rather than as a one-off number. If a result seems unexpected, doctors will often recommend repeating the test to confirm it before acting on it.

  • How do I book Autonomic sweat testing privately?

    You can typically book a private blood test online or by phone, often without needing a GP referral, and be seen within a few days. Results are usually reviewed by a doctor who can explain what they mean and recommend any next steps or further investigations. Get in touch with the clinic to check current availability and what's included with the test.