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At a Glance 

The issue: Many people with ME/CFS and Long COVID experience clear symptoms of orthostatic intolerance (OI) — feeling significantly worse when upright — but are told their autonomic testing is “normal” because they don’t meet criteria for POTS or orthostatic hypotension (OH). 

Key distinction: POTS is one specific cause of OI, not the whole picture. Orthostatic intolerance is a broader category, and the absence of a POTS diagnosis does not rule out other causes of OI, including other forms of dysautonomia. 

What research shows: A 2024  study co-authored by a Johns Hopkins physician found that ME/CFS patients with normal heart rate and blood pressure responses during tilt table testing still showed abnormal reductions in cerebral blood flow and cardiac output — a likely explanation for why OI symptoms can be present even when standard thresholds for POTS or OH aren’t met. 

The diagnosis gap: Most clinical settings only measure heart rate and blood pressure during orthostatic testing. Specialized cerebral blood flow measurements are rarely available in a clinical setting, leaving many patients without an explanation for their symptoms. 

What BHC recommends: 

• OI is a clinical diagnosis based on symptoms and function, not just numerical thresholds 

• The 10-Minute NASA Lean Test (aka Passive Stand Test) is an accessible, validated tool clinicians can use to evaluate OI beyond POTS criteria 

• Patients should feel empowered to ask clinicians about broader OI evaluation even if POTS has been ruled out 

The bottom line: Growing POTS awareness is a start, but ME/CFS and Long COVID patients need clinical pathways that recognize the full spectrum of orthostatic intolerance — even when POTS criteria aren’t met. 

This “At a Glance” section was created by AI and then edited by a human to ensure accuracy.  

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When “It’s Not POTS” Doesn’t Mean “It’s Not Dysautonomia”

A familiar story shows up again and again in patient communities: 

You stand up, and your body acts like it’s running uphill: dizziness, weakness, nausea, “brain fog,” a sudden heavy fatigue, sometimes shortness of breath or chest discomfort. You do a tilt table test or a standing test. The results come back: you don’t meet criteria for POTS (postural orthostatic tachycardia syndrome). Your blood pressure doesn’t drop enough for orthostatic hypotension. You’re told the test is “normal.” 

And yet, your symptoms are anything but. 

At Bateman Horne Center (BHC), we hear this frequently from people with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and Long COVID (also called Post-Acute Sequelae of SARS-CoV-2 infection or PASC), especially those who experience clear, reproducible symptoms when upright but don’t “fit” the most recognized boxes. 

The problem isn’t that these symptoms are rare. The problem is that our testing and diagnostic habits often spotlight only a subset of what dysautonomia can look like. 

First, a quick translation: what is dysautonomia, and what is orthostatic intolerance? 

Dysautonomia is an umbrella term for dysfunction of the autonomic nervous system, the body’s “automatic” regulator for things like heart rate, blood pressure, blood vessel tone, temperature, digestion, sweating, and more. 

Orthostatic intolerance (OI) is a symptom pattern: feeling worse when upright (standing, sitting, walking) and feeling better when lying down. It can include lightheadedness, cognitive slowing, weakness, tremulousness, palpitations, headache, nausea, visual changes, and profound fatigue. 

Importantly: 

• POTS is one specific type of dysautonomia and only one cause of orthostatic intolerance. 

• Orthostatic intolerance is bigger than POTS. 

This distinction sounds small, but it matters enormously because clinical care often stops at, “No POTS, therefore no dysautonomia.” 

Why so many people fall through the cracks. 

Most common orthostatic tests focus on a narrow set of measurements: 

• Heart rate (HR) 

• Blood pressure (BP) 

Those are definitely important, but sometimes they aren’t the whole story. You can have debilitating orthostatic symptoms without dramatic changes in HR or BP. 

That pattern has been documented in ME/CFS research using more advanced physiologic measurements during tilt table testing, especially measurements of cerebral blood flow (how much blood is reaching the brain). 

What the research is suggesting: “Normal” HR and BP can be falsely reassuring because abnormal brain blood flow may still be present. 

A 2024 study by researchers at Johns Hopkins and in the Netherlands examined a large group of people with ME/CFS who had a normal heart rate and blood pressure response during a tilt table test, but also had additional measurements taken, including cardiac output (how much blood the heart pumps) and cerebral blood flow (how much blood reaches the brain).  

They found that among ME/CFS patients with normal HR/BP responses during tilt, most still showed abnormal reductions in cerebral blood flow and cardiac output while upright, which is a physiologic signal that could help explain why someone can feel dramatically worse when standing even if their HR and BP don’t meet classic thresholds.  

This doesn’t mean every person with ME/CFS or Long COVID needs specialized cerebral blood flow testing. But it does support a crucial point: 

Orthostatic intolerance can be severe and measurable, even when standard criteria for POTS or hypotension are not met. 

Why the U.S. diagnosis gap persists. 

If you’re thinking, “So why don’t more clinics measure cerebral blood flow during tilt testing?” you are not alone. 

In many regions, even basic orthostatic assessment using HR and BP can be a challenge. Adding specialized Doppler-based measurements (which require equipment and specialized expertise) is even less common. 

That leaves many in a bind: 

• The symptoms are classic for orthostatic intolerance. 

• The most familiar labels (POTS, orthostatic hypotension) may not apply. 

• The testing most people can access may not capture what’s going wrong. 

Long COVID has increased awareness. 

Autonomic symptoms are increasingly recognized in Long COVID, including orthostatic intolerance and POTS-like presentations. Reviews and studies have described substantial autonomic symptom burden in PASC and emphasize the value of autonomic testing for appropriate diagnosis and management.  

Just as in ME/CFS, not everyone with Long COVID dysautonomia neatly meets POTS criteria, yet they may still experience disabling upright symptoms consistent with orthostatic intolerance. 

What BHC wants patients and clinicians to know. 

Here is a message BHC emphasizes in clinical care and education: 

Orthostatic intolerance is ultimately a clinical diagnosis, rooted in symptoms and function, not only a checkbox based on one threshold. 

POTS can be an important “door-opener” diagnosis (and it’s good that awareness is growing). But focusing only on POTS can unintentionally erase the experience of people who have clear orthostatic intolerance that doesn’t present as tachycardia. 

A practical step forward: the 10-Minute NASA Lean Test (a Passive Stand Test) 

While specialized cerebral blood flow testing is uncommon, there are still accessible ways to evaluate orthostatic intolerance in many clinical settings. 

BHC has long advocated for the 10-Minute NASA Lean Test, a standardized passive standing test that can be performed in outpatient clinics and, when appropriate, can also help patients document patterns over time with clinician guidance.  

BHC’s provider instructions describe orthostatic intolerance as an umbrella term and outline how to perform the test in a structured way.  

For more information on how the 10-Minute NASA Lean Test was used to study OI in ME/CFS patients read our paper published in the medical journal, Work. 

If you’ve been told, “Your test is normal,” but you feel worse upright. 

If you recognize yourself in this story, you’re not imagining it and you’re not alone. 

Consider bringing these points to a clinician (or using them to guide a follow-up conversation): 

• “Orthostatic intolerance is broader than POTS, can we evaluate OI even if I don’t meet POTS criteria?” 

• “Could we do a structured standing assessment like the 10-Minute NASA Lean Test?” 

• “Can we discuss symptom-triggered patterns (standing, sitting upright, showering, cooking, waiting in line) and what improves when I lie down?” 

(As always, any testing should be discussed with a clinician who understands your medical history and safety considerations.) 

The bottom line. 

POTS awareness has helped many people finally get a name for what they’re experiencing. But for ME/CFS and Long COVID communities, the next step is just as important: 

We need broader recognition that orthostatic intolerance and dysautonomia can exist even when POTS criteria are not met—and we need clinical pathways that don’t end at “no POTS.” 

BHC will continue supporting efforts to: 

• improve routine orthostatic measurements, 

• educate clinicians about the full spectrum of orthostatic intolerance, 

• and translate emerging research, like the measurement of cerebral blood flow during tilt testing, into clearer, compassionate care

Knowledge Shared. Lives Changed.

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