Someone in your support group swears salt saved her life. You tried it for three weeks, felt like a water balloon with a headache, and quietly concluded that you were failing at your own illness. You weren't. You may simply not have her POTS.

That sentence sounds strange, because POTS arrives as a single label. One acronym, one diagnosis, one Facebook group. But underneath the label are at least three different bodies doing three different things to produce the same racing heart. Until you know which body you live in, every piece of advice you receive is a coin flip, and every failed coin flip feels like a verdict on you.

The illness that isn't one thing

POTS is defined by a measurement, not a cause. Your heart rate climbs by 30 beats per minute or more within ten minutes of standing, 40 or more if you are a teenager, without the blood pressure drop that would make it orthostatic hypotension, and the symptoms have lasted at least three months. That is the whole definition. It describes what happens. It is silent about why.

The why is where people diverge. Autonomic researchers have long described three overlapping mechanisms: neuropathic, hyperadrenergic, and hypovolemic. The major expert consensus statements treat these as mechanisms rather than formal diagnoses, because most people have a blend. But the dominant mechanism in your body shapes what you feel, what triggers you, and which treatments actually land. Knowing yours is the difference between following advice and following the right advice.

Neuropathic POTS: the legs that forgot how to squeeze

When a healthy person stands, gravity pulls roughly half a liter of blood into the legs and belly. Within seconds, small sympathetic nerve fibers tell the veins and arterioles down there to constrict, pushing blood back toward the heart. You never notice it. It is one of the quietest reflexes you own.

In neuropathic POTS, those nerve fibers in the lower body are damaged or underactive, a partial autonomic neuropathy. The legs do not get the message to squeeze. Blood pools, less returns to the heart, each heartbeat moves less volume, and the heart speeds up to compensate for what the legs failed to do. Studies supporting this picture include reduced sweating in the feet on autonomic sweat testing, lower norepinephrine release in the legs than expected, and, in a subset of patients, loss of small nerve fibers on skin biopsy.

If this is your body, you probably know it. Your legs feel heavy and turn mottled or purple when you stand. Heat is your enemy, because it dilates the vessels that already will not tighten. Compression, counterpressure maneuvers, salt and fluids, and medications that constrict blood vessels tend to help, because they all address the same problem: blood sitting in the wrong place. Your blood pressure, meanwhile, usually stays fairly steady while your heart rate climbs.

Hyperadrenergic POTS: the alarm with no off switch

Now picture a body where the sympathetic nervous system is not too quiet but far too loud. When a person with hyperadrenergic POTS stands, the body pours out norepinephrine, the hormone of fight or flight. Researchers use a standing plasma norepinephrine level of 600 picograms per milliliter or higher as a marker. Blood pressure often rises on standing instead of holding steady, sometimes by ten points or more.

This changes the texture of the experience entirely. The heart does not just race, it pounds. Hands tremble and go cold and clammy. Migraines, flushing, and a sense of dread that arrives before any thought does are common. Caffeine, stimulant medications, and emotional stress can make it dramatically worse, because they add fuel to a fire that is already burning. A rare inherited form, caused by a faulty norepinephrine transporter that fails to clear the hormone from the synapse, was described in a single family and helped researchers understand the mechanism. A notable overlap with mast cell activation, which brings flushing and hives, has also been reported in a subset.

Here is the part that explains the salt mystery. Loading volume into a body whose problem is excessive nerve signaling does not fix the signaling. Many people in this group report that aggressive salt and fluids leave them bloated and headachy without touching the surges. Clinicians often reach instead for medications that damp sympathetic drive or slow the heart directly. Same diagnosis, opposite logic.

Hypovolemic POTS: the tank that runs low

The third body has less blood in it. Studies measuring plasma volume in POTS patients have found that a substantial portion run genuinely low, sometimes by a significant fraction. Stranger still, their kidneys do not respond the way kidneys should. Normally low blood volume triggers the hormones renin and aldosterone to make the body hold onto salt and water. In many POTS patients, those hormones are paradoxically low. The retain-fluid signal is muted. Researchers call this the renin-aldosterone paradox, and it means the body is quietly under-filled and not trying hard enough to fix it.

Deconditioning layers on top. Weeks and months of lying down shrink the heart's stroke volume, so each beat moves even less. Some investigators have described a smaller-than-expected heart on imaging in a portion of POTS patients, though how much is cause and how much is consequence remains debated.

If this is your body, mornings are brutal, because overnight you lose fluid and wake at your lowest. Thirst is constant. An IV bag at urgent care feels like a miracle for a day. Salt, fluids, and medications that help the kidney retain them tend to help the most, and graded exercise done lying or seated gradually rebuilds the volume and the heart's capacity to move it.

Why the forum's advice keeps missing you

There is a well-documented tendency in human psychology, formalized by Leon Festinger as social comparison theory, to evaluate ourselves against people we perceive as similar. It is how we calibrate what is normal and what is possible. Online, similarity is defined by a shared diagnosis label. You and the woman who swears by salt are in the same group, so her outcome becomes your yardstick.

But the label is hiding the mechanism. Her legs may not squeeze while your nervous system screams. You are comparing yourself to the wrong reference class, and the inevitable mismatch gets filed not as a biology problem but as a character one. You did not try hard enough. You did not drink enough. Everyone else figured it out.

None of that is true. The failure was not in your effort. It was in the assumption that one body's fix should work in another body with a different fault. Letting go of that assumption is not giving up on treatment. It is the beginning of treatment that fits.

Your next moves

  • Run a stand test with a blood pressure cuff, not just a heart rate. Lie flat for five minutes and record both numbers. Stand and record again at two, five, and ten minutes. Write down whether your systolic pressure rose by ten or more, held steady, or dipped. That single detail points toward a mechanism and is worth more to your doctor than any description.
  • Trial one change at a time for two weeks and log it. Salt loading, compression, cutting caffeine, each alone. Rate your worst standing moment each day from one to ten. Overlapping changes make every result uninterpretable.
  • Write your trigger fingerprint. List every reliable trigger: heat, meals, standing still, stimulants, emotional stress, mornings. Circle the top three. A heat and standing profile suggests pooling. A stress and caffeine profile suggests sympathetic overdrive. A mornings and thirst profile suggests volume.
  • Bring two specific questions to your next appointment. Ask whether measuring your norepinephrine lying down and then standing is appropriate, and whether autonomic testing such as a sweat test or skin biopsy makes sense for you. Specific questions get specific answers.
  • Before trying any new tip, ask what it is fixing. Blood in the wrong place, too much nerve signal, or not enough blood. If the answer does not match your profile, you can skip it without guilt.

The pattern is already in your body

The three mechanisms above are not an exam you have to pass. They are a lens, and most people's bodies show the pattern plainly once someone looks for it across days instead of moments. Stable was built for exactly that kind of looking. It logs your stand tests with heart rate and blood pressure side by side, tracks which triggers reliably precede your worst hours, and lets you record each intervention trial so the two-week logs above become a chart your doctor can read in thirty seconds. Over time it stops being a diary and starts being a map of which body you live in. If you would like help drawing that map, you can start at stable.lumenlabs.works.