What people mean by fluid volume in POTS.
Blood volume is simply how much blood is circulating in your body. When it runs low — the medical word is hypovolemia — less blood returns to the heart when you stand, and the heart compensates by beating faster. That is the same mechanism that gives POTS its name, so you can see why volume became a central thread in POTS research.
The Heart Rhythm Society's expert consensus reports that blood volume is reduced in up to 70 percent of people with POTS. Measurement studies put numbers on it: in one comparison, people with POTS carried a plasma volume deficit averaging about 13 percent, while the healthy comparison group had essentially none.
The part researchers still cannot explain.
If your blood volume were low, you would expect your body's fluid-conserving machinery to switch on hard. The renin-angiotensin-aldosterone system does exactly that in most circumstances — it signals the kidneys to hold onto salt and water. In POTS, it often does not behave that way. The consensus describes patients who are low on volume yet show low renin activity and low aldosterone, the opposite of the expected response. Researchers have called this a paradox that remains unexplained.
There is a second honest caveat. Low blood volume is common in POTS, but it is not universal and it is not the whole story. More recent measurement work describes POTS pathophysiology as heterogeneous and overlapping — meaning several mechanisms exist across different patients, and volume is one of them rather than the explanation for everyone.
Both points land in the same place: a finding that describes 70 percent of a research population cannot tell you which group you are in. Only measurement and clinical judgment can do that.
Why this is not a reason to load up on salt and water.
The consensus statement does describe increased daily water and dietary salt for patients known or strongly suspected to be low on volume, if tolerated. But read how that guidance is rated: the authors classify it as "may be considered" and assign it their lowest evidence level — expert opinion rather than trial evidence. That is a cautious suggestion for individual patients a clinician has examined, not a population-wide instruction.
Extra sodium is genuinely risky for some people. MedlinePlus notes that healthy adults are advised to stay under 2,300 mg of sodium daily, that adults with high blood pressure are advised to stay under 1,500 mg, and that people with congestive heart failure, liver cirrhosis, or kidney disease may need considerably less. In those same conditions, too much sodium can drive a serious buildup of fluid in the body. Aggressive fluid intake carries its own hazards.
So this page gives no amounts and no intake advice on purpose. If salt or fluid changes might help you, that is a decision to reach with a clinician who knows your blood pressure, your kidneys, your heart, and your medications — not one to copy from a webpage, a video, or someone else's POTS routine.
How clinicians approach volume in POTS.
The Heart Rhythm Society consensus directs clinicians to examine patients for hypovolemia as part of evaluation. NINDS separately notes that current treatment approaches focus on managing low blood volume and blood-flow problems. What it does not offer is a standardized bedside method for judging volume status — another reason this gets decided case by case rather than by formula.
Your own observations are useful raw material for that conversation. The consensus documents that POTS symptoms are commonly worsened by dehydration, heat, alcohol, and exercise, so a record of what makes yours better or worse is worth bringing to an appointment. Note these things; do not use them to draw your own conclusions:
- Whether mornings are different from the rest of your day, and whether drinking fluids changes how you feel.
- Whether heat — hot weather, hot showers, a warm room — reliably makes symptoms worse.
- Whether you find yourself drawn to salty foods, and when that started.
- What you currently drink and eat on a normal day, described honestly rather than aspirationally.
- Every medication and supplement you take, including anything affecting blood pressure or fluid balance.
Questions worth asking when you call.
POTS is among the chronic neurological concerns the practice's published material describes working with. Care at Gates Brain Health is complementary functional neurology: it runs alongside your primary care provider and cardiologist rather than in place of them, and decisions about medications and intake targets stay with the clinicians who make them. What an examination here involves is described on the treatment page.
If you are considering a call to (775) 507-2000, these questions tend to make the conversation more productive:
- Has my blood volume ever actually been measured, or has it been assumed?
- Given my blood pressure, kidney function, and heart history, is any salt or fluid change safe for me to discuss?
- Which of my current medications affect fluid balance?
- How would an evaluation here fit with what my cardiologist or primary care provider has already found?
- Which records should I bring — recent labs, ECGs, tilt-table results?
When something needs attention before any of this.
Fainting that injures you, fainting during exertion, chest pain, or severe breathlessness are not fluid-volume questions to work through at home. Those belong in front of emergency clinicians right away — dial 911 or get to an emergency department. If dizziness or near-fainting has recently become noticeably worse, tell your primary care provider or cardiologist without waiting for a routine appointment.