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Autonomic Testing
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Lab Tests

Autonomic Testing

Autonomic testing evaluates how well your autonomic nervous system (ANS) functions, helping to identify the cause of symptoms related to involuntary body processes.

Overview

Autonomic testing helps determine if your autonomic nervous system (ANS) is working as it should. Your ANS controls body functions that happen automatically, such as breathing, heartbeat, body temperature, and digestion. Problems with the function of your ANS are known as autonomic neuropathy, which damages the nerves controlling your internal organs.

Symptoms

Autonomic neuropathy can affect various systems in the body. Symptoms vary depending on which part of the nervous system is affected:

  • Stomach and gastrointestinal: Constipation, diarrhea, nausea, and vomiting.
  • Bladder and urinary: Difficulty urinating, leaking urine, or urinating more often than usual.
  • Heart and lung: Rapid heart rate, shortness of breath with activity, dizziness, fainting, and weakness.
  • Other: Abnormal sweating, sexual problems (such as erectile dysfunction or vaginal dryness), pupils slow to adjust to light, and low blood glucose without typical warning symptoms.

Diagnosis & Testing

Depending on your symptoms, your provider may perform one or more of the following tests:

  • Deep Breathing Test and Valsalva Maneuver: Measures heart rate and blood pressure during specific breathing patterns.
  • Tilt Table Test: Monitors blood pressure and heart rate while changing your posture to investigate lightheadedness or fainting.
  • Quantitative Sudomotor Axon Reflex Test (QSART): Measures the function of nerves that control sweating using a mild electrical current.
  • Thermoregulatory Sweat Test (TST): Assesses how well your body sweats in a heated environment.
  • Bladder Ultrasound: Checks for bladder function issues by measuring residual urine after urination.

Preparation & Risks

Preparation often includes avoiding caffeine for eight hours, alcohol for 12 hours, and tobacco for four hours before the test. Stay well-hydrated with non-caffeinated beverages the day before. Regarding risks, some people may faint during a tilt table test, and others may experience temporary nausea or weakness. Sweat tests may cause minor skin irritation from electrodes.

Results

If results are not normal, it indicates a potential problem with your ANS. Your provider will interpret these findings alongside your medical history, physical exam, and symptoms to determine a diagnosis and treatment strategy, which may include lifestyle changes or medication.

Frequently Asked Questions

Most clinicians advise stopping short‑acting antihypertensives (e.g., beta‑blockers, clonidine) 24–48 hours before the test, but you should follow your provider’s specific instructions. Long‑acting medications may be continued if they are essential, but discuss risks and benefits with your doctor.
Risks are minimal but can include fainting, dizziness, or a brief drop in blood pressure. Tests are performed in a controlled setting with continuous monitoring, and staff are trained to intervene immediately if symptoms arise. Patients are advised to avoid caffeine, alcohol, and nicotine before testing to reduce variability.
Patients who experience unexplained lightheadedness, fainting spells, rapid heartbeat, or dizziness that worsens when standing or after meals are often referred for a tilt table test to assess orthostatic intolerance or vasovagal syncope. Severe or persistent symptoms that interfere with daily life also warrant evaluation.
The test usually takes 30–60 minutes. You will lie on a table that gradually tilts to a 70–80° angle while your heart rate and blood pressure are monitored. You may feel lightheaded or nauseous; the technician will stop the tilt if you become uncomfortable. After the test, you’ll rest until your vitals return to baseline.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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