Treatment · Autonomic · Self-management
Hydration
Drinking enough fluid — often paired with extra salt, though not for everyone — is one of the first and cheapest steps when long COVID has unsettled your autonomic nervous system and circulation.
Short version: fluid — often with added salt to help your body hold onto it — expands blood volume and eases the racing heart and dizziness of POTS. But salt is not right for everyone: if you need to limit sodium, hydration still matters, just managed differently (see When extra salt isn’t the right lever). Individualize with a clinician, especially with high blood pressure, heart failure, or kidney disease.
Why it matters in long COVID
Many people with long COVID develop dysautonomia and POTS. When you stand, gravity pulls blood toward your legs and abdomen; a healthy autonomic system tightens blood vessels and adjusts heart rate to keep the brain supplied. In long COVID that reflex often misfires — and a large share of people with POTS also turn out to be hypovolemic, with a measured blood (plasma) volume lower than their body size predicts.
Less volume in the system means more blood pools in the legs on standing, a sharper compensatory heart-rate rise, and the orthostatic intolerance — dizziness, lightheadedness, brain fog — and orthostatic tachycardia that can make being upright the hardest part of the day. Adding fluid is the most direct way to put volume back.
How hydration helps
Drinking more fluid raises the volume of plasma in your blood vessels. With more to work with, less blood drains from the central circulation when you stand, so the heart does not have to race as hard to compensate. Salt matters because water on its own is quickly excreted; sodium helps your body retain the fluid you drink — which is why salt and fluid loading are commonly recommended together rather than water alone. Salt is the usual lever — but it is not the only one, and it is not safe for everyone; if sodium is something you need to limit, see below.
What the evidence says
For POTS and orthostatic intolerance generally, expanding blood volume with fluid and salt is considered foundational, first-line self-management. Short-term studies show that higher sodium intake can blunt the orthostatic heart-rate rise and lower the surge of stress hormones that comes with standing. Typical guidance for POTS is on the order of two to three litres of fluid and a markedly higher salt intake per day, adjusted with a clinician.
How precisely these POTS findings transfer to every case of post-COVID dysautonomia is still being worked out — the biology is sound and the step is low-risk for most people, but it is rarely a complete answer on its own.13
Doing it safely
More is not always better. Drinking large volumes of plain water without enough salt can dilute the body’s sodium (hyponatremia) and is not the goal. Aggressive salt and fluid loading is not appropriate for everyone — particularly people with high blood pressure, heart failure, or kidney disease — so the salt side especially should be cleared with a clinician.
In practice, spreading fluids through the day, adding electrolytes, and taking a larger drink before getting up tends to help more than occasional big gulps. Hydration supports the other autonomic measures rather than replacing them — and if you have post-exertional malaise, it should sit alongside pacing, never a push to exert.
Managing your electrolytes
Hydration is really an electrolyte question: sodium holds water in the bloodstream, but potassium and magnesium matter too, and the right balance is individual — especially if you need to limit salt. That has its own page. Managing electrolytes covers what each one does, why balance beats loading any single one, how oral rehydration actually works, and what to do when sodium must be limited.
Related approaches
Hydration is the foundation that the other autonomic treatments build on: salt and fluid loading formalises the salt side, fludrocortisone helps the body hold onto salt and water, compression garments reduce the pooling that fluid loading also targets, and midodrine tightens blood vessels. Most people combine several.
References
Every reference is free to read in full.