Symptoms and what sits behind them
POTS and Dysautonomia: The Blood Tests That Rule Out Look-Alikes
Reviewed by a qualified clinician · analysed at UKAS-accredited UK labs (ISO 15189)
Last reviewed September 20266 min read
Every Helvy guide is written by our health editors, then checked by a qualified clinician before it goes live and re-checked as the science moves. We name clinical roles, not individuals, until each reviewer has agreed to be credited publicly. This is wellness guidance to help you understand your own data, not a diagnosis.
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PoTS is diagnosed with a stand test, not a blood test. Your heart rate rises by more than 30 beats a minute within 10 minutes of standing. Blood tests come first, to rule out look-alikes. PoTS UK lists thyroid tests, morning cortisol, ferritin, B12, folate, vitamin D, glucose and a full blood count.
You stand up in a queue and your heart takes off. The edges of the room go grey, and you need to sit down on the floor.
If that keeps happening, you may have come across PoTS, or the wider word dysautonomia. As of September 2026, the NHS page on PoTS was last reviewed in July 2026, and interest has grown alongside long COVID. Before anyone gives it a name, some ordinary and fixable causes need ruling out. That part is a blood test.
By the Helvy Medical Team · Reviewed by a qualified clinician · 6 min read
1. What is PoTS, and how is it diagnosed?
PoTS stands for postural tachycardia syndrome. The NHS describes it as your heart rate rising after you get up from sitting or lying down, often making you dizzy or lightheaded. You may also see it written POTS, for postural orthostatic tachycardia syndrome.
Dysautonomia is the umbrella term. Your autonomic nervous system runs the things you never think about, like heart rate and blood pressure. When it misfires, that is dysautonomia. PoTS is one form.
The diagnosis is about numbers on a heart monitor. The charity PoTS UK sets out the criteria:
A GP checks this with an active stand test: heart rate and blood pressure lying down, then again after you stand. The NHS says PoTS is more likely if you have long COVID, ME or chronic fatigue syndrome, or joint hypermobility syndrome.
“It can take time for people to be diagnosed with PoTS as the symptoms are similar to other conditions.”
NHS, Postural tachycardia syndrome (PoTS)
2. Which blood tests rule out the look-alikes?
PoTS UK lists the bloods usually taken to rule out other conditions: a full blood count, kidney function, ferritin, vitamin B12, folate, thyroid tests, morning cortisol, glucose, vitamin D and a coeliac screen. Here is why the main ones are on it.
Is it your thyroid?
An overactive thyroid is the classic look-alike. The NHS lists an irregular or unusually fast heart rate, anxiety and feeling tired all the time among its symptoms. Two markers cover it. TSH is the signal your brain sends to tell the thyroid how hard to work. Free T4 is the hormone the thyroid actually makes.
Is it your adrenal glands?
Cortisol is a hormone your adrenal glands make, and it helps hold your blood pressure up. When they make too little, as in Addison’s disease, the NHS lists feeling dizzy or lightheaded when standing up. It is rare. That is why PoTS UK asks for a morning cortisol, when levels should be at their highest. Our guide to low cortisol symptoms explains the timing.
Are your iron stores low?
Ferritin is the protein that holds iron in reserve, so it shows how much iron you have banked. Low iron stores turn up often in PoTS. In a 2013 US study of 24 teenagers with PoTS, half had low iron stores. Among US teenagers in general, it was 14%.
That is a small study and a link, not a cause. But low ferritin is easy to find and easy to act on. Ferritin can also be low before a full blood count shows anaemia. More in our ferritin blood test guide.
What about B12, folate and vitamin D?
Vitamin B12 and folate are B vitamins your body needs to make healthy red blood cells. The NHS lists palpitations, shortness of breath and problems with balance among the symptoms of a B12 or folate deficiency. Those overlap with PoTS almost line for line.
Vitamin D is on the list too. In a 2011 US review of 188 teenagers with fatigue or dizziness on standing, 22% had low vitamin D and 47% had low iron stores. Again, a pattern rather than proof.
3. What can a blood test not tell you about PoTS?
It cannot confirm PoTS, and it cannot rule it out. Normal bloods clear the look-alikes, which is useful. The heart rate test is still the one that answers the question.
Some tests on the PoTS UK list are GP tests rather than home ones: a full blood count, glucose and a coeliac screen. An ECG, which records your heart’s rhythm, is usually part of the workup too. Our guide to heart palpitations blood tests covers what that side of things looks like.
Before the appointment, jot down your heart rate lying down and then after a few minutes standing. A smartwatch reading is a clue for your GP, not a diagnosis.
Some symptoms cannot wait for any test. The NHS says to call 999 if chest pain comes on suddenly and does not go away, spreads to your arm, jaw or back, or comes with sweating or feeling sick.
4. How do you check these markers?
Start with your GP. The NHS says to see one if you have symptoms of PoTS, and the stand test and ECG only happen there. Say when it started and what brings it on.
If you want to see your own numbers alongside that, our General Energy & Wellness panel (£149) measures TSH, free T4, cortisol, vitamin B12, vitamin D, urea and creatinine among 17 markers. Take the sample before 10am so the cortisol reading means something.
For the iron side, the Vitamins & Minerals panel (£159) measures ferritin, iron, transferrin and transferrin saturation, plus B12, folate, vitamin D and magnesium.
Either way, results are information to discuss with a qualified clinician, not a diagnosis. For the wider picture of feeling wiped out, see our energy and fatigue hub, or our guide to dizziness blood tests.
Frequently asked questions
Can a blood test diagnose POTS?
No. PoTS is diagnosed by measuring your heart rate lying down and then standing, usually with an active stand test or a tilt table test. Blood tests are there to rule out other conditions that cause the same symptoms.
Which blood tests should I have before a POTS diagnosis?
PoTS UK lists a full blood count, kidney function, ferritin, vitamin B12, folate, thyroid tests, morning cortisol, glucose, vitamin D and a coeliac screen. Your GP decides which of these you need.
Can low iron cause POTS symptoms?
Low iron stores are common in people with PoTS. In a small US study of teenagers with PoTS, half had low iron stores, against 14% of teenagers in general. That is a link, not proof that low iron causes PoTS.
Can an overactive thyroid feel like POTS?
It can. The NHS lists an unusually fast or irregular heart rate, anxiety and feeling tired all the time among the symptoms of an overactive thyroid. TSH and free T4 show which way your thyroid is running.
Is dysautonomia the same as POTS?
Not quite. Dysautonomia means the autonomic nervous system, which runs your heart rate and blood pressure without you thinking, is not working properly. PoTS is one type of dysautonomia.
What if all my blood tests are normal?
Normal bloods do not rule PoTS in or out. They rule other things out, which is the point. Take the results back to your GP and ask for an active stand test if you have not had one.
Clear the look-alikes off the list
Our General Energy & Wellness panel (£149) measures TSH, free T4, cortisol, vitamin B12 and vitamin D among 17 markers. Home finger-prick kit, results usually within 5 working days of the lab receiving your sample, from UKAS-accredited UK laboratories.
Medical disclaimer: This content is for informational purposes only and does not constitute medical advice, diagnosis, or treatment. Study figures describe small groups and may not apply to you. Blood tests measure biomarkers; they do not diagnose PoTS or its cause. Do not change medication or treatment based solely on this article. Call 999 for sudden chest pain that does not go away. Consult your GP or a qualified healthcare professional. All Helvy blood tests are processed by UKAS-accredited UK laboratories to ISO 15189.
Last updated: September 2026 · By Helvy · Medically analysed at UKAS-accredited UK laboratories
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