Is POTS Part of ME/CFS? Why Standing Up Is So Hard in Chronic Fatigue
What standing up does in ME/CFS, and where POTS fits among the patterns a stand or tilt test can show.
Photo: Sou Jest / Unsplash
Is POTS part of ME/CFS? Not exactly. POTS (postural orthostatic tachycardia syndrome) and ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome) are separate diagnoses that often turn up in the same person. What connects them is a broader problem called orthostatic intolerance, which means symptoms get worse while you're upright and ease when you lie down. It's written into the diagnostic criteria for ME/CFS, and POTS is only one of the ways it shows up on testing.
What is orthostatic intolerance, and where does POTS fit?
Orthostatic intolerance is the umbrella term for an experience: lightheadedness, brain fog, heavy tiredness, nausea, or a pounding heart that builds while you stand or sit up and settles once you lie flat. Several measurable patterns can produce it.
POTS is one of those patterns. In several of the studies below, it was defined as the heart rate climbing by 30 beats per minute or more on a stand or tilt test, or going past 120. Orthostatic hypotension is another, where the top blood pressure number falls by 20 points or more. A third is low carbon dioxide in the breath while upright, called hypocapnia, which usually reflects breathing more than the body needs.
POTS also isn't always the starting point. Different disease conditions can produce symptoms of POTS, where the POTS is not the primary thing, so the thing to look for is what's driving it. For someone with ME/CFS, that makes a POTS result one clue in a larger workup rather than the whole explanation.
Why does standing feel so hard with ME/CFS?
In 2015, the Institute of Medicine proposed new diagnostic criteria for ME/CFS. They require a substantial drop in activity with fatigue, post-exertional malaise (a delayed worsening after effort), and unrefreshing sleep. A diagnosis also needs at least one of two more features, either cognitive problems or orthostatic intolerance. So feeling worse upright can be one of the features that completes the diagnosis.
A 2020 study by van Campen and colleagues at a Dutch cardiology clinic looked at one reason it can feel so bad. They tilted 429 adults with ME/CFS upright for up to 30 minutes and used ultrasound on the neck arteries to measure blood flow to the brain. By the end of the tilt, 44 healthy controls had lost about 7% of that flow. The ME/CFS group lost 26%. People who met the POTS cutoff lost 29%, while people whose heart rate and blood pressure stayed normal still lost 24%.
Using a cutoff drawn from the healthy controls, 82% of that normal-looking group had an abnormal drop. Larger drops went with more symptoms during the tilt. Van Campen's team pointed out that these patients would have been classed as having normal circulation if only heart rate and blood pressure had been measured. The study came from one specialty clinic that may have been sent more patients with orthostatic symptoms, and people who were bedbound weren't tested.
How many people with ME/CFS have POTS?
Published estimates differ widely. A 2008 British study by Hoad and colleagues used a two-minute stand in 59 people with ME/CFS and found POTS in 27%, compared with 9% of matched controls. In van Campen's tilt study, described above, 28% met the POTS cutoff. A Dutch study by Roerink and colleagues tested 419 people with chronic fatigue syndrome (CFS) using an active standing test. POTS turned up in only 5.7% of adults, which wasn't different from the 6.9% seen in fatigued patients who didn't meet CFS criteria. The authors concluded that checking for POTS appears to be of limited value for diagnosing CFS.
In 2026, Novak and colleagues reported tilt-table results for 170 people with ME/CFS at a Boston autonomic lab. POTS turned up in 19% of them. Another 15% had neurogenic orthostatic hypotension, where blood pressure falls on standing because the nerves that should tighten the blood vessels don't respond. Slower blood flow to the brain during the tilt was one of the most common findings, seen in 88%, alongside signs of widespread autonomic strain in 89%.
Those studies differ in how long people stood, whether they were tilted, and which clinic referred them, so I read the spread as a sign that the number depends on how the test was run. Long COVID, one form of post-viral illness, shows a similar picture. Novak's lab found POTS in 22% of the 143 long COVID patients it tested. In a 2026 Dublin study by O'Brien and colleagues, half of 50 long COVID patients had orthostatic symptoms on a lean test, and 32% had postural tachycardia.
What does a stand or lean test measure?
In the NASA lean test protocol that Natelson and colleagues used, a person lies flat for at least 10 minutes to get resting numbers. Then they stand with their feet together about six to eight inches from a wall and lean back against it for 10 minutes. Heart rate, blood pressure, breathing rate, and exhaled carbon dioxide are recorded every minute.
Their 2022 study at Mount Sinai repeated the test in 63 people with ME/CFS over up to three yearly visits. Of those 63, 60.3% had an abnormal result at some visit. Low carbon dioxide was the most common finding, more common than POTS, and the authors wrote that it would be missed without a carbon dioxide monitor. Anxiety scores were similar whether or not someone had low carbon dioxide. The specific abnormality often changed between visits.
Testing for this is something to arrange through a clinician who can read the results alongside your history. If post-exertional malaise is one of your symptoms, it's reasonable to ask how to plan around the test day, the same way pacing within an energy envelope decides how you plan everything else.
What if your stand test came back normal?
A normal heart-rate result answers a narrow question: whether the heart rate passed a set cutoff in that test, on that day. The studies above found three things a heart-rate cutoff can't capture. Brain blood flow fell further than normal in the large majority of people whose heart rate and blood pressure looked fine, low carbon dioxide only shows up when someone measures it, and the abnormality can change between visits.
That is why feeling worse upright deserves attention even with a normal result, along with the question of what's driving it. If it comes with gut symptoms that change when you stand, bring that up too. Getting care for ME/CFS is often hard, and a diary noting position, time upright, and what eases it can make an appointment more productive. The chronic fatigue hub has more on ME/CFS and post-viral illness.
If chronic fatigue is part of your picture, ME/CFS, Reconsidered is an upcoming course on ME/CFS, post-viral fatigue, and pacing. You can join The Weekly Well, our free newsletter, to hear when the course opens.
FAQ
Is POTS the same thing as ME/CFS?
No. POTS describes how the heart rate responds to standing, and ME/CFS is a wider illness defined by reduced activity with fatigue, a crash after exertion, and unrefreshing sleep. The two often overlap, and the 2015 ME/CFS criteria name orthostatic intolerance as one of two features that can complete the diagnosis.
What is the difference between POTS and orthostatic intolerance?
Orthostatic intolerance is the broad category: symptoms that build while you're upright and ease when you lie down. POTS is one specific pattern inside it, where the heart rate rises by 30 beats per minute or more (40 or more in teenagers) on a stand or tilt test, without a drop in blood pressure. Low blood pressure on standing and low carbon dioxide from overbreathing are other patterns.
How common is POTS in people with ME/CFS?
In the studies covered here, estimates run from about 6% to 28%, depending on the clinic and the test. A large Dutch study using an active standing test found 5.7% of adults, while a Dutch cardiology clinic using tilt testing found 28% and a British study using a two-minute stand found 27%. A Boston autonomic lab using tilt testing found 19%. The number depends heavily on how the test was done.
Can you have orthostatic intolerance with a normal tilt test?
Yes. In a Dutch study of 429 adults with ME/CFS, 82% of those with a normal heart rate and blood pressure response still had an abnormal drop in blood flow to the brain while tilted. That measurement isn't part of a routine tilt test, so a normal result answers a narrower question than it seems to.
What is a NASA lean test?
It's a 10-minute test where you lie down to get resting numbers, then stand and lean your back against a wall while heart rate and blood pressure are recorded every minute. Some clinics also measure breathing rate and exhaled carbon dioxide. It should be done with a clinician, who can make sense of it in the context of your other symptoms.
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