Plasma Norepinephrine Testing: The Blood Test That Identifies Hyperadrenergic POTS

Of all the POTS subtypes, hyperadrenergic POTS is the one most frequently missed — not because it is rare, but because its defining feature (elevated norepinephrine upon standing) requires a specific blood test that most doctors never order. Patients with hyperadrenergic POTS often spend years being told their symptoms are anxiety, panic disorder, or simply "a fast heart rate," when in fact they have a measurable, biochemically distinct form of dysautonomia that responds to very different treatments than other POTS subtypes.

This article explains what plasma norepinephrine testing is, how it is performed, what the results mean, and why it is the single most important diagnostic test for identifying hyperadrenergic POTS.

What Is Norepinephrine and Why Does It Matter in POTS?

Norepinephrine (also called noradrenaline) is a catecholamine neurotransmitter and hormone released by the sympathetic nervous system. When you stand up, your sympathetic nervous system activates to maintain blood pressure and heart rate against gravity — and norepinephrine is the primary chemical messenger of this response. It causes blood vessels to constrict, the heart to beat faster and harder, and the adrenal glands to release additional catecholamines.

In healthy individuals, standing causes a modest increase in plasma norepinephrine — typically from a supine level of 100–300 pg/mL to a standing level of 200–500 pg/mL. This is a normal, controlled sympathetic response.

In hyperadrenergic POTS, this response is dramatically exaggerated. Standing causes norepinephrine levels to surge — often to 600, 800, 1,000 pg/mL or higher. This excessive norepinephrine release drives the characteristic features of hyperadrenergic POTS: extreme tachycardia, hypertension (rather than the hypotension seen in other POTS subtypes), tremor, anxiety-like symptoms, sweating, and a feeling of internal vibration or "adrenaline rush."

The Diagnostic Threshold for Hyperadrenergic POTS

The standard diagnostic criterion for hyperadrenergic POTS is a standing plasma norepinephrine level ≥ 600 pg/mL, measured after 10 minutes of standing. This threshold was established by research from Vanderbilt University's Autonomic Dysfunction Center, the leading center for POTS research in the United States.

Some specialists use a more stringent criterion: a standing norepinephrine ≥ 600 pg/mL combined with a supine-to-standing increase of ≥ 300 pg/mL. This helps distinguish true hyperadrenergic POTS from patients who have a high standing norepinephrine simply because they have a high baseline.

It is important to note that not all patients with elevated standing norepinephrine have hyperadrenergic POTS. Norepinephrine can be elevated in other conditions including pheochromocytoma (a rare adrenal tumor), paraganglioma, severe anxiety, and in patients taking certain medications. The clinical context — particularly the presence of orthostatic tachycardia meeting POTS diagnostic criteria — is essential for interpretation.

How the Test Is Performed

Plasma norepinephrine testing for POTS requires careful standardization to produce meaningful results. The protocol used at most autonomic centers is:

Step 1: Supine baseline. The patient lies flat for at least 20–30 minutes. A blood sample is drawn from an indwelling IV catheter (to avoid the catecholamine surge from venipuncture itself). This is the supine norepinephrine level.

Step 2: Standing sample. The patient stands upright for exactly 10 minutes. A second blood sample is drawn from the same IV catheter. This is the standing norepinephrine level.

The 10-minute standing protocol is critical. Norepinephrine levels continue to rise with prolonged standing, and drawing the sample too early (at 2–3 minutes) may underestimate the true standing level. Drawing at 10 minutes captures the plateau of the sympathetic response.

Some centers perform a modified protocol during the tilt table test, drawing blood at 45 degrees of tilt rather than full upright standing. This is acceptable but may produce slightly lower values than true upright standing.

Preparation for the Test

Accurate plasma norepinephrine testing requires careful preparation:

Medications to hold (typically 48–72 hours, confirm with your doctor):

• Beta-blockers (propranolol, metoprolol, atenolol) — significantly suppress norepinephrine release
• Alpha-agonists (midodrine, clonidine) — affect sympathetic tone
• SNRIs (venlafaxine, duloxetine) — inhibit norepinephrine reuptake and raise plasma levels
• Tricyclic antidepressants — similar mechanism to SNRIs
• Stimulants (amphetamines, methylphenidate) — increase norepinephrine release

Day of test:

• Avoid caffeine for 24 hours
• Avoid vigorous exercise for 24 hours
• Fast for 4 hours before the test (food can affect catecholamine levels)
• Arrive calm and rested — anxiety and pain elevate norepinephrine

Important: Do not stop any medication without explicit guidance from your physician. The medication hold list must be individualized based on your specific medications and medical history.

Interpreting Your Results

A standing norepinephrine ≥ 600 pg/mL in a patient who meets POTS diagnostic criteria (orthostatic heart rate increase ≥ 30 bpm, or ≥ 40 bpm in patients under 19) is diagnostic of hyperadrenergic POTS.

If the standing norepinephrine is ≥ 1,000 pg/mL, most specialists will also order a 24-hour urine catecholamines and metanephrines (or plasma metanephrines) to rule out pheochromocytoma, even if the clinical picture strongly suggests POTS. Pheochromocytoma is rare but dangerous, and the consequences of missing it are severe.

Why Hyperadrenergic POTS Responds Differently to Treatment

Understanding the hyperadrenergic mechanism changes treatment decisions significantly:

Beta-blockers work differently in hyperadrenergic POTS. In standard POTS, low-dose propranolol (10–20 mg) is often helpful. In hyperadrenergic POTS, higher doses may be needed because the excessive norepinephrine drive is stronger. However, non-selective beta-blockers (propranolol) are generally preferred over cardioselective ones (metoprolol) in hyperadrenergic POTS because they block both the cardiac (beta-1) and vascular (beta-2) effects of norepinephrine.

Clonidine is particularly effective. Clonidine is a central alpha-2 agonist that reduces sympathetic outflow from the brain, directly addressing the excessive norepinephrine release. It is one of the most effective treatments for hyperadrenergic POTS and is often used when beta-blockers alone are insufficient.

Fludrocortisone and midodrine are less effective. These medications work by expanding blood volume and increasing vascular tone — mechanisms that address hypovolemic and neuropathic POTS. In hyperadrenergic POTS, the problem is excessive sympathetic drive, not inadequate volume or vascular tone. These medications may even worsen hypertension in hyperadrenergic patients.

Stimulants are contraindicated. Medications that increase norepinephrine (amphetamines, methylphenidate, some decongestants) can dramatically worsen hyperadrenergic POTS and should be avoided unless there is a compelling reason and careful monitoring.

The Genetic Forms of Hyperadrenergic POTS

A subset of hyperadrenergic POTS is caused by specific genetic mutations:

NET (norepinephrine transporter) deficiency is caused by mutations in the SLC6A2 gene. The norepinephrine transporter normally clears norepinephrine from the synapse after release. When it is deficient, norepinephrine accumulates — producing the hyperadrenergic phenotype. This is an autosomal dominant condition and can be identified by genetic testing.

COMT (catechol-O-methyltransferase) variants affect norepinephrine metabolism. The Val158Met polymorphism in COMT affects enzyme activity and has been associated with altered catecholamine metabolism in some POTS patients.

If you have hyperadrenergic POTS and a family history of similar symptoms, genetic testing through a dysautonomia specialist or genetic counselor may be informative.

Getting the Test Ordered

Plasma norepinephrine testing is not routinely ordered by most primary care physicians or cardiologists. It is most commonly ordered by:

• Autonomic neurologists
• Dysautonomia specialists
• Cardiologists with expertise in POTS
• Some electrophysiologists

If your doctor is unfamiliar with the test, you can reference the Vanderbilt Autonomic Dysfunction Center's published protocols or the consensus statement on POTS from the Heart Rhythm Society (2015), which includes plasma norepinephrine as a recommended test for POTS subtype classification.

The test requires a laboratory that can process catecholamine samples correctly — the blood must be drawn into a chilled EDTA tube, placed on ice immediately, and processed within 30 minutes. Not all laboratories have this capability. Your autonomic specialist's office will typically coordinate with a reference laboratory (such as Mayo Medical Laboratories or Quest Diagnostics) that handles catecholamine testing correctly.