Hi Friend
If you live with hEDS, MCAS, fibromyalgia, ME, or you are on your LDN journey, there is a good chance you know this feeling. Your heart races for no reason. You go lightheaded when you stand. You are bone-tired but wired. Your temperature swings, your gut has a mind of its own, and you crash for days after doing very little. And you have almost certainly been told, more than once, that your tests are normal.
There is often a single system misfiring underneath all of it, and it has a name. Dysautonomia. This month we are going right into it: what it is, the biology of why it happens, why it sits at the very centre of the conditions in our community, why it so often has to be treated first, how it is assessed, and what genuinely helps. This is a long read. If this is your world, it may be one of the more useful things you read this year.
What is dysautonomia?
Dysautonomia is an umbrella term for a malfunction of the autonomic nervous system, the part of the nervous system that runs everything you never consciously think about. Your heart rate. Your blood pressure. Your digestion. Your temperature. Your breathing. Your bladder. Your sweat glands. Even the size of your pupils and the timing of your hormones. It makes thousands of tiny adjustments every hour to keep your internal environment stable while the world around you changes.
In dysautonomia, that automatic regulation stops being smooth. The system over-reacts, under-reacts, or fires at the wrong moment. Because the autonomic nervous system reaches almost every organ, the symptoms are scattered across the entire body. That is the single biggest reason it gets missed. A cardiologist sees the palpitations, a gastroenterologist sees the gut, a rheumatologist sees the pain, and each one, looking at their slice in isolation, finds nothing dramatic. Nobody is looking at the control system that ties them together.
The biology: what the autonomic nervous system actually does
To understand why treating it matters so much, it helps to understand how it is meant to work.
The system has two main branches that behave like an accelerator and a brake. The sympathetic branch is the accelerator, the fight or flight response, driven largely by adrenaline and noradrenaline. It speeds the heart, tightens blood vessels, raises alertness, and diverts energy to the muscles. The parasympathetic branch is the brake, the rest and digest state, carried mostly by the vagus nerve. It slows the heart, lowers arousal, and switches on digestion, repair and recovery.
Good health is not about being in one state or the other. It is about shifting fluidly between them at the right moments, revving up when you need to and braking properly afterwards. In dysautonomia that flexibility is lost. A great many people in our community are effectively stuck with the accelerator jammed down and a weak brake, running in a low-grade fight or flight state around the clock. That is exactly why you can feel utterly exhausted and buzzing with adrenaline at the same time, why your sleep does not refresh you, and why your body never seems to drop into proper recovery.
Two mechanisms are worth knowing by name, because they explain so many symptoms:
The baroreflex. Pressure sensors in your major arteries constantly measure your blood pressure and tell the brain to adjust heart rate and vessel tightness to keep it steady. When this reflex is sluggish or dysregulated, standing up, which should trigger an instant compensation, instead lets blood pool downwards, and you feel it as dizziness, greying vision or a pounding heart.
Blood volume and pooling. Many people with these conditions run on a lower circulating blood volume than they should, and their vessels hold blood poorly. Less fluid in the system, and vessels that do not clamp down properly, means less blood reaching the brain when upright. This is why fluids, salt and compression, which sound almost too simple, are foundational rather than trivial.
Why dysautonomia is the centre of the whole picture, and why we treat it first
This is the part I most want you to take away, because it changes how you approach getting better.
Think of your autonomic nervous system as the engine room of the body. It governs blood flow, oxygen delivery, digestion, sleep, temperature and the stress response. When the engine room is in chaos, every other system downstream struggles, no matter how well you try to treat each one on its own. You can have the right pain plan, the right gut plan, the right mast cell plan, and still feel like you are getting nowhere, because the foundation underneath them is unstable.
Here is why it acts as a bottleneck. If your blood is pooling and your brain is under-perfused, you will have brain fog and fatigue that no supplement will fix. If your body is stuck in fight or flight, your sleep cannot do its repair work, your digestion is switched off at the wrong times, and your mast cells are more easily triggered. If your heart is racing every time you stand, you cannot build the gentle activity tolerance that helps almost everything else. Left unaddressed, dysautonomia quietly blocks the benefit of nearly every other treatment you try.
That is why, in practice, stabilising the autonomic system tends to be the first building block, not the last. When you steady the foundation, restore blood volume, calm the overactive accelerator, improve tolerance to being upright, several things often happen at once. The fatigue lifts a little. The fog clears a little. Sleep deepens. Mast cell reactivity settles. Pain becomes more manageable. Not because you treated each of those separately, but because you treated the system they all depend on. Get the engine room working, and everything built on top of it has a chance to respond.
None of this means the other conditions do not matter or do not need their own treatment. hEDS, MCAS, fibromyalgia and ME each have their own biology and their own management. The point is one of order and foundation. Dysautonomia is the shared layer beneath them, and when it is ignored it holds the whole recovery back. Treat it as the groundwork, and the rest of the plan finally has something solid to stand on.
The symptoms, grouped by system
Because it is a whole-body control system, the symptoms span every system at once. This is often the giveaway that you are dealing with dysautonomia rather than an isolated organ problem.
Heart and circulation: racing or pounding heart, palpitations, chest discomfort, dizziness or fainting on standing, greying or tunnelling vision when upright, cold or blotchy hands and feet
Energy and brain: profound fatigue out of all proportion to activity, brain fog, poor concentration, word-finding difficulty, and post-exertional crashes lasting hours or days
Temperature and skin: running too hot or too cold, poor heat tolerance, drenching sweats or an inability to sweat, flushing
Gut: nausea, bloating, early fullness, reflux, constipation or unpredictable bowels, and a gut that feels slow and switched off
Sleep and nervous system: unrefreshing sleep, difficulty falling asleep despite exhaustion, adrenaline surges especially at night, tremor, anxiety-like states that are physical rather than emotional
Bladder and other: urinary urgency and frequency, dizziness in the shower or after meals, and symptoms that reliably worsen with heat, standing, illness or your menstrual cycle
If you are recognising yourself across several of those groups, that pattern is itself meaningful. You are not imagining it, and you are not simply anxious. These are real, physical, measurable disturbances in a real, physical control system.
The main types you are most likely to meet
Dysautonomia is a family of conditions, not one diagnosis. The forms most relevant to our community include:
Postural orthostatic tachycardia syndrome, or PoTS. The best known in this space. On standing, blood pools in the lower body and the heart races to compensate. The hallmark is a sustained rise in heart rate of at least 30 beats per minute within ten minutes of standing, or 40 in teenagers, without a large drop in blood pressure. There are recognised sub-patterns worth knowing about, because they respond to different things. In the hyperadrenergic pattern the body pumps out too much noradrenaline, giving tremor, surges and high standing blood pressure. In the low-volume pattern the core problem is too little circulating blood. In the neuropathic pattern the small nerves that should tighten the leg vessels are not doing their job.
Orthostatic hypotension. Here the blood pressure itself falls on standing, causing lightheadedness and faintness.
Inappropriate sinus tachycardia. A resting heart rate that sits too high without a clear reason.
Broader autonomic dysfunction affecting digestion, temperature, sweating and bladder, which can be present with or without the classic heart rate changes.
Knowing your pattern matters, because the right support for a low-volume picture is not the same as for a high-adrenaline picture.
Why dysautonomia clusters with each of our conditions
This is what lets one newsletter speak to hEDS, MCAS, fibromyalgia, ME and Long Covid at the same time. The links are not vague. Each has a mechanism.
hEDS and hypermobility. In hypermobile people, connective tissue is more stretchy, and that includes the walls of the veins. Stretchier vessels pool more blood when you are upright, so the heart has to work harder to return it to the brain. On top of that, the connective tissue changes may affect the small nerves and the tissues the autonomic system relies on. This is a major reason PoTS and hEDS travel together so often, and why, together with mast cell activation, they form a trio that appears far more frequently than chance alone would explain.
MCAS. Mast cells release a cocktail of chemical messengers, including histamine, that act directly on blood vessels, heart rate and nerves. When mast cells are overactive, they can trigger flushing, drops in blood pressure, racing heart and gut symptoms, all of which are autonomic. And it runs both ways: being stuck in fight or flight makes mast cells more twitchy, so the two drive each other in a self-sustaining loop. Break into that loop by calming the autonomic side, and the mast cell side often becomes easier to settle too.
Fibromyalgia. The evidence increasingly points to autonomic dysfunction and central sensitisation sitting underneath fibromyalgia. A nervous system stuck in overdrive, that cannot brake into recovery, amplifies pain signals and disrupts sleep. When people reframe their fibromyalgia with the autonomic piece included, symptoms that had been dismissed as unexplainable often start to make sense.
ME. The hallmark of ME, post-exertional malaise, that delayed crash after even small exertion, overlaps heavily with autonomic and circulatory dysfunction. Poor blood flow on standing, low blood volume and an inability to recover all feed the exhaustion. This is also why aggressive exercise advice has done so much harm here, and why gentle, autonomically-aware pacing matters so much.
Long Covid. One of the clearest lessons of recent years is that a viral trigger can leave lasting autonomic damage behind it, with PoTS-like illness becoming common after infection. It has brought dysautonomia to the attention of a whole new group of people, and reinforced that a nervous system knocked out of balance can stay that way long after the original trigger has gone.
Where LDN fits into the conversation
Many of you are on, or curious about, low dose naltrexone, so let us be clear and honest about where it sits.
LDN is not a direct treatment for dysautonomia in the way that fluids, salt and compression directly support blood volume and standing tolerance. Its relevance comes from a different and complementary angle. LDN is thought to work partly by briefly blocking opioid receptors, prompting the body to rebound with more of its own natural endorphins, and partly by calming immune cells in the nervous system called microglia, reducing what is known as neuroinflammation, the low-grade inflammation in and around the nerves that is increasingly implicated in fibromyalgia, ME and the overlap conditions.
Why does that matter for dysautonomia? Because a nervous system that is inflamed and sensitised is a nervous system that regulates poorly. If neuroinflammation is part of what keeps the autonomic system misfiring and the pain system amplified, then calming it may make the foundation easier to stabilise. Think of LDN not as a fix for the autonomic problem itself, but as one tool that can lower the background noise the whole system is fighting against, working alongside the more targeted autonomic strategies rather than replacing them. Whether it is right for you is always an individual decision, made with a clinician who knows your history.
How dysautonomia is assessed
The genuinely encouraging news, after years of normal tests, is that this is measurable. Assessment often begins with something very simple:
The active stand test, or the NASA lean test. Your heart rate and blood pressure are recorded lying down, and then repeatedly over ten minutes of standing or leaning. The pattern over those ten minutes is what reveals the problem, which is precisely what a single rushed reading in a GP room misses. This simple test is often the moment years of dismissed symptoms finally show up in black and white.
The tilt table test. A more formal hospital version, where you are tilted upright on a table while monitored continuously.
Blood tests to exclude mimics. Thyroid problems, anaemia, low iron, low B12, coeliac disease, diabetes and adrenal issues can all produce overlapping symptoms and are worth ruling out, because sometimes there is a treatable contributor sitting alongside.
Wider assessment of the cluster, because looking at the autonomic picture, the mast cell picture, the hypermobility and the gut together gives a far truer map than any one test alone.
A practical tip that can change an appointment. If you have dizziness on standing, ask specifically for your heart rate and blood pressure to be measured lying down and then standing, held over several minutes, not just a single seated reading. That one request can surface a pattern that has been hiding for years. It is also worth keeping a simple symptom and heart rate diary before you go, as patterns over time are powerful evidence.
What actually helps
Management is very individual, and the biggest gains usually come from stacking several small, consistent measures rather than hunting for one magic fix. The foundations, roughly in the order they tend to matter, are:
Fluids. Increasing fluid intake raises circulating blood volume, so there is more to go around and less pooling. This is basic but genuinely powerful.
Salt. For many people, increasing dietary salt helps the body hold onto that fluid. This is the one to be careful with. If you have high blood pressure, or any heart or kidney condition, do not increase your salt without checking with your clinician first.
Compression. Waist-high compression garments physically reduce pooling in the legs and abdomen and can noticeably improve standing tolerance.
Position and daily habits. Rising slowly, avoiding long spells standing still, tensing the legs before and while standing, keeping cool in the heat, and eating smaller meals to avoid the post-meal blood flow crash.
Pacing. Working within your energy envelope to avoid the boom and bust cycle, which is especially vital where ME and post-exertional malaise are involved.
Movement, carefully and gradually. Often starting in a reclined or supported position, such as a recumbent bike, rowing or water-based movement, building slowly over months. Done gently this retrains tolerance. Done too hard too soon it backfires badly, so patience beats effort here.
Treating the rest of the cluster. Settling mast cell reactivity, supporting the gut, improving sleep and managing pain all reduce the load on the autonomic system, because these systems are wired together. This is the two-way street again: calm the foundation and the rest eases, ease the rest and the foundation steadies.
Medication where appropriate. There are prescription options that target specific patterns, for example the low-volume versus the high-adrenaline pictures. These are individual decisions for your clinician, and they work best on top of the foundations above, not instead of them.
The thread running through all of it is the same as the theme of this whole newsletter. Steady the engine room first. Give the rest of your treatment a stable foundation to work from.
A final word
If this has put a name to something you have carried for years without one, hold onto this. Your symptoms are real, they are connected, and, crucially, they are both measurable and workable. Understanding dysautonomia is so often the moment the whole bewildering picture finally clicks into place, and from there, with the foundation addressed first, real progress becomes possible.
At Mend Clinic we assess the whole picture, the autonomic foundation alongside the conditions that sit on top of it, rather than chasing each symptom in isolation. I have now opened my dates for 1-1 consultations in November and they can be booked here
Warm wishes,
Dr Ahmed
This newsletter is for general education and does not constitute personal medical advice. Always consult a suitably qualified clinician about your own health, and before making any changes such as increasing your salt intake.
