You have probably been told to drink more water. It is the first advice most people with POTS hear, often before they have a diagnosis, sometimes from a stranger who watched them go pale and sit down on a curb. So you drink. You carry a liter bottle everywhere. And still, somewhere between standing up and crossing the kitchen, your heart climbs into the hundreds, the room tilts, and the water you have been dutifully sipping seems to have done nothing at all.
It did not fail because you weren't trying. It failed because water, on its own, does not stay where you need it.
POTS Is Often a Blood Volume Problem
Postural orthostatic tachycardia syndrome is usually described in terms of heart rate—the sustained jump of 30 beats per minute or more within ten minutes of standing. But the racing heart is a symptom, not the cause. It is the body's compensation for something happening lower down: when you stand, gravity pulls roughly a half-liter of blood into the veins of your legs and abdomen. In a healthy system, vessels clamp down and the muscle pump pushes that blood back up. In POTS, that return falls short, less blood reaches the heart, and the only way to keep cardiac output steady is to beat faster. That tachycardia is your heart doing the work of two systems that aren't holding up their end.
Here is the part that reframes everything: a large fraction of people with POTS are running on less blood than they should be. Studies of plasma and red-cell volume have found that many patients are measurably hypovolemic—not dehydrated in the way a hiker is dehydrated, but chronically under-filled, sometimes by a substantial margin. When the tank is low to begin with, even a normal shift of fluid into the legs tips the system over the edge. You are not failing to hydrate. You are starting every stand from a deficit.
Why Plain Water Slips Through
This is where the water-bottle strategy quietly breaks down. The volume that matters for orthostatic tolerance is the volume inside your blood vessels. To hold fluid there, you need sodium. Water follows salt; that is one of the most reliable rules in physiology. Drink plain water without enough sodium on board and a good portion of it is simply filtered out by the kidneys and sent to the bladder—which is also why so many people with POTS find themselves urinating constantly while still feeling parched and lightheaded. The fluid arrived. It just didn't stay.
Sodium changes that math. It raises the osmotic pull that keeps water in the bloodstream and signals the kidneys to hold on rather than dump. This is why the standard first-line, non-drug advice from autonomic specialists pairs the two together—increased salt and increased fluid—rather than treating hydration as a solo act. The salt is not a garnish. It is the thing that turns the water you drink into the blood volume you can stand on.
There is a further twist that makes this counterintuitive. You might assume a body short on blood volume would be frantically conserving salt. In a meaningful subset of POTS patients, the opposite shows up: the renin–aldosterone system—the hormonal cascade that normally tells the kidneys to retain sodium when volume is low—runs inappropriately quiet. The very mechanism that should be defending blood volume is underperforming. So the dietary salt is not just topping up a normal system; for some people it is compensating for a signal that isn't firing the way it should. This is also why salt and fluid loading is something to do with a clinician, not freelance—blood pressure, kidney function, and conditions like hypertension or heart failure all change the calculus, and the right amount is genuinely personal.
The Glass of Water That Works in Minutes
There is one hydration trick that does work fast, and it is worth knowing because it feels like cheating. If you drink a tall glass of water quickly—not sip it, drink it—your body produces a brief, measurable rise in blood pressure and a blunting of the standing heart-rate spike within about fifteen to thirty minutes. Researchers studying orthostatic intolerance have documented this "water pressor response" repeatedly. The trigger appears to be the stretch of the stomach and the dilution of fluid in the gut sensed by the nervous system, which nudges sympathetic tone upward. The effect is temporary, lasting perhaps an hour, but the timing is the gift.
It means a fast glass of water before you get out of bed, before you stand to give a presentation, before you walk into a warm shower or a long grocery line, is not a placebo. It is a short, reliable lever. People who have lived with POTS for years often discover this by accident and build their whole morning around it. The point is to do it on purpose, and at the moments that actually cost you.
Volume Is a System, Not a Sip
Fluid loading is one pillar, but blood volume responds to a whole posture of small habits, and they reinforce each other. Compression garments—waist-high, ideally—physically narrow the venous space in the legs and abdomen so less blood pools there in the first place, which means the volume you have is doing more work. Avoiding long, motionless standing, and using physical counter-maneuvers like crossing your legs and tensing the muscles or doing a quiet calf pump while you wait, recruits the skeletal muscle that helps push blood back toward your heart. Even the temperature of a room matters, because heat dilates vessels and enlarges the space your blood has to fill. None of these are cures. Together they are the difference between a system that copes and one that constantly overdraws.
What makes salt and water the foundation is that it is the only one of these that directly addresses the underlying deficit rather than working around it. The others manage the consequences of low volume. This one raises the volume.
The Hard Part Is Knowing If It's Working
Here is the genuinely difficult thing about treating a blood-volume problem at home: you cannot feel your plasma volume. You can only feel its downstream effects—how dizzy you are on the stairs, how long you last upright, how hard your heart works to keep you conscious. And those effects lag, shift with the weather, the menstrual cycle, your sleep, a bad night, a hot afternoon. Try to judge whether more salt is helping by how you feel on any single day and you will be reading noise. The signal lives in the pattern across weeks: standing heart rate trending down, the upright minutes trending up, the crash days getting rarer.
That pattern is exactly what is hard to hold in your head and easy to lose to memory. Stable was built for this slow, unglamorous work—logging your standing heart rate, your salt and fluid intake, your symptoms and energy, so that a change you made in one week becomes something you can actually see two weeks later. It will not tell you how much sodium to eat; that is a conversation for you and your doctor. What it can do is turn your own body into the experiment it already is, and give you the record that tells you whether the experiment is working. If you are tired of guessing, you can start tracking the pattern at stable.lumenlabs.works—and bring something better than a hunch to your next appointment.