Can POTS Show Up in Bloodwork?

Routine blood tests do not diagnose POTS
Normal bloodwork does not rule POTS out
Labs can help identify other causes of similar symptoms

Patients with dizziness, a racing heart, weakness, fatigue, or brain fog may undergo extensive blood testing and be told that the results are normal.

That can raise an important question: Can POTS show up in bloodwork?

Usually, no. There is no routine blood test that confirms postural orthostatic tachycardia syndrome (POTS). A person with POTS can have normal bloodwork because the diagnosis depends primarily on symptoms and what happens to heart rate and blood pressure when the person becomes upright.

Bloodwork still has an important role. It can help identify anemia, electrolyte abnormalities, thyroid disease, dehydration, and other medical problems that may cause or contribute to symptoms that resemble POTS.

Why doesn’t POTS usually show up on routine bloodwork?

POTS is defined by a physiological response to upright posture rather than by a specific abnormality in the blood.

A blood sample taken while a patient is sitting or lying down does not show how the heart rate and blood pressure respond after standing.

Current diagnostic criteria generally require chronic orthostatic symptoms together with a sustained increase in heart rate of at least 30 beats per minute in adults within 10 minutes of standing or head-up tilt. For adolescents ages 12 through 19, the threshold is at least 40 beats per minute.

The heart-rate increase occurs without the sustained blood-pressure decrease that defines classical orthostatic hypotension. Other conditions that could explain the tachycardia also need to be considered.

This is why the diagnosis is based on the overall clinical pattern rather than a single laboratory result. A more detailed discussion is available in how do you know if you have POTS?

Can you have POTS with normal bloodwork?

Yes. Normal routine blood tests do not rule out POTS.

A patient may have a normal complete blood count, normal electrolytes, and normal thyroid testing and still demonstrate the characteristic orthostatic heart-rate response and symptoms of POTS.

This distinction is important because normal laboratory results should not automatically end the evaluation when a patient consistently becomes lightheaded, weak, shaky, cognitively impaired, or tachycardic while standing.

At the same time, normal bloodwork does not prove that POTS is present. Symptoms such as dizziness, palpitations, fatigue, weakness, and brain fog can occur in many different conditions.

Why do doctors order blood tests when evaluating POTS?

Blood tests are useful because several medical conditions can cause tachycardia and orthostatic symptoms that resemble POTS.

The 2021 National Institutes of Health expert consensus review recommended that laboratory evaluation include, at a minimum, a complete blood count, electrolytes, and thyroid function testing, with additional testing guided by the patient’s clinical presentation.

The purpose is not to find a blood marker that proves POTS. It is to look for other explanations or contributing conditions.

What blood tests may be considered?

The laboratory evaluation should be individualized rather than identical for every patient.

Depending on the history and clinical presentation, testing may include:

• a complete blood count to look for anemia
• electrolytes and kidney function
• thyroid function testing
• ferritin or iron studies when iron deficiency or blood loss is a concern
• glucose or other metabolic testing when clinically indicated
• additional nutritional, endocrine, inflammatory, or other testing based on the patient’s symptoms and history

The goal is to determine whether another condition explains the tachycardia or contributes to the patient’s symptoms.

Why is a complete blood count useful?

Anemia can produce symptoms that overlap substantially with POTS.

Patients with anemia may experience fatigue, weakness, dizziness, palpitations, exercise intolerance, shortness of breath, or an increased heart rate. These symptoms may become more noticeable during activity or while upright.

A complete blood count can identify anemia, but the cause may require additional evaluation. Blood loss, iron deficiency, nutritional deficiencies, chronic illness, and other conditions may need to be considered.

Anemia is one of several conditions discussed further in what illnesses can mimic POTS?

Why are thyroid tests often checked?

Thyroid disease can affect heart rate, energy, temperature regulation, and exercise tolerance.

Hyperthyroidism, in particular, can produce tachycardia, palpitations, tremulousness, heat intolerance, sweating, weakness, and fatigue. Several of these symptoms overlap with POTS.

When hyperthyroidism adequately explains the sinus tachycardia, the clinical picture should not simply be labeled POTS.

This illustrates why laboratory testing is important even though bloodwork itself does not diagnose POTS.

What about dehydration and electrolyte abnormalities?

Dehydration can produce a rapid heart rate, dizziness, weakness, and orthostatic symptoms.

Vomiting, diarrhea, fever, inadequate fluid intake, excessive sweating, blood loss, or medications such as diuretics may reduce circulating volume and make symptoms worse while standing.

Electrolyte abnormalities may also contribute to weakness, palpitations, or other symptoms.

Low blood volume can occur in patients with POTS as well, so the distinction is not always simple. The clinical question is whether an acute or identifiable problem such as dehydration better explains the tachycardia or whether the patient has a persistent orthostatic syndrome.

Can iron deficiency matter even without severe anemia?

Iron studies may be useful when the history suggests iron deficiency, menstrual or gastrointestinal blood loss, nutritional concerns, or unexplained fatigue.

Ferritin reflects iron stores, while a complete blood count evaluates whether anemia is present. A patient can have depleted iron stores before developing substantial anemia.

However, finding iron deficiency does not automatically establish the cause of every orthostatic symptom. Laboratory findings still need to be interpreted in the context of the patient’s history, symptoms, and cardiovascular response to standing.

Are there specialized blood tests for some patients with POTS?

Yes, but these are different from routine bloodwork and are not required to diagnose every patient with POTS.

In selected patients, clinicians or autonomic centers may measure plasma catecholamines, including norepinephrine, while the patient is lying down and after becoming upright.

This type of testing may help characterize excessive sympathetic activation in patients suspected of having a hyperadrenergic pattern of POTS.

It is important not to confuse specialized physiological testing with a routine diagnostic blood test. An abnormal catecholamine result may help characterize a patient’s autonomic physiology, but POTS remains a clinical syndrome defined primarily by orthostatic symptoms and cardiovascular responses to standing.

How is POTS actually diagnosed?

The evaluation begins with the patient’s symptoms and their relationship to posture.

Heart rate and blood pressure are typically measured after the patient has been resting and again at intervals while standing. A 10-minute standing test can often demonstrate the characteristic orthostatic tachycardia.

A tilt-table test may be useful when the diagnosis remains uncertain, symptoms are difficult to reproduce safely, or more detailed autonomic evaluation is needed.

An electrocardiogram is also commonly part of the initial evaluation, and ambulatory heart monitoring may be considered when an arrhythmia or inappropriate sinus tachycardia is suspected.

Blood pressure matters as well as heart rate. The distinction between the two major orthostatic patterns is discussed in POTS vs orthostatic hypotension.

What if the bloodwork is normal but symptoms continue?

Normal bloodwork should be interpreted as one part of the evaluation rather than as proof that nothing is wrong.

If symptoms consistently worsen while standing, it may be useful to examine what happens to heart rate, blood pressure, and symptoms during upright posture.

Some patients have significant orthostatic or autonomic symptoms without meeting the formal heart-rate criteria for POTS. That broader distinction is discussed in autonomic dysfunction without POTS.

Conversely, symptoms that resemble POTS can arise from cardiac, endocrine, hematologic, medication-related, infectious, neurologic, or other conditions. A normal routine laboratory panel cannot identify or exclude every possible explanation.

Where does Lyme disease fit?

Patients with Lyme disease may report fatigue, dizziness, palpitations, weakness, exercise intolerance, and cognitive difficulties that overlap with symptoms reported in POTS.

POTS and broader autonomic abnormalities have also been reported during or after Lyme disease, although the published evidence remains limited and does not establish that Lyme disease explains every case of POTS.

Routine bloodwork cannot determine whether a patient with Lyme disease has POTS. The same orthostatic heart-rate, blood-pressure, symptom, and timing criteria still need to be considered.

Likewise, abnormal Lyme disease testing does not establish that dizziness or tachycardia is caused by POTS. The clinical patterns should be evaluated separately and then considered together.

Frequently Asked Questions

Can POTS show up in routine bloodwork?

Usually not. There is no routine blood test that diagnoses POTS. Bloodwork is primarily used to identify conditions such as anemia, electrolyte abnormalities, thyroid disease, or other problems that may cause or contribute to similar symptoms.

Can you have POTS if all your blood tests are normal?

Yes. A patient can have normal routine bloodwork and still have POTS. The diagnosis depends primarily on chronic orthostatic symptoms and the characteristic heart-rate and blood-pressure response to standing rather than on a specific laboratory abnormality.

What blood tests are commonly checked when POTS is suspected?

A complete blood count, electrolytes, and thyroid function tests are commonly considered. Additional testing such as iron studies or other metabolic, nutritional, endocrine, or inflammatory tests may be ordered based on the patient’s history and symptoms.

Can anemia look like POTS?

Yes. Anemia can cause fatigue, weakness, dizziness, palpitations, exercise intolerance, shortness of breath, and tachycardia. Because these symptoms overlap with POTS, anemia should be considered during the evaluation.

Is there a specific blood marker for POTS?

No routinely accepted blood biomarker establishes the diagnosis of POTS. Specialized testing such as upright plasma catecholamines may be useful in selected patients to characterize autonomic physiology, but it is not a routine diagnostic blood test for POTS.

Does normal bloodwork mean my dizziness and racing heart are not medical?

No. Routine blood tests do not measure the cardiovascular response to standing and cannot exclude every cause of dizziness or tachycardia. Persistent or significant symptoms still warrant evaluation based on the clinical pattern and appropriate testing.

Clinical Takeaway

POTS usually does not show up on routine bloodwork because it is defined primarily by symptoms and the cardiovascular response to upright posture rather than by a specific blood abnormality.

Blood testing remains important because anemia, electrolyte abnormalities, thyroid disease, dehydration, and other medical problems can cause or contribute to symptoms that resemble POTS.

Normal bloodwork therefore does not rule out POTS, while abnormal bloodwork does not automatically explain every orthostatic symptom.

The key diagnostic question is not simply what appears in the blood, but what happens to symptoms, heart rate, and blood pressure when the patient stands.

Related Articles

These articles explore POTS symptoms, triggers, treatment, and the relationship between POTS and Lyme disease.

What Triggers POTS? Infections and Other Triggers
How Is POTS Treated? Treatment Options Explained
What Does a Bad Day With POTS Feel Like?
POTS in Lyme Disease: Why You Feel Worse Standing

References

1. Vernino S, Bourne KM, Stiles LE, et al. Postural orthostatic tachycardia syndrome (POTS): State of the science and clinical care from a 2019 National Institutes of Health Expert Consensus Meeting — Part 1. Autonomic Neuroscience. 2021;235:102828.
2. Raj SR, Fedorowski A, Sheldon RS. Diagnosis and management of postural orthostatic tachycardia syndrome. CMAJ. 2022;194(10):E378-E385.
3. Sheldon RS, Grubb BP II, Olshansky B, et al. 2015 Heart Rhythm Society expert consensus statement on the diagnosis and treatment of postural tachycardia syndrome, inappropriate sinus tachycardia, and vasovagal syncope. Heart Rhythm. 2015;12(6):e41-E63.

Dr. Daniel Cameron, MD, MPH
Lyme disease clinician with over 30 years of experience and past president of ILADS.

Symptoms • Testing • Coinfections • Recovery • Pediatric • Prevention