The NIH’s RECOVER study, one of the largest long COVID studies ever funded, identified 12 signature symptoms that define the condition. Published in JAMA, these findings gave researchers and clinicians a concrete framework for recognizing long COVID, which the WHO defines as symptoms lasting at least two months that appear roughly three months after a COVID-19 infection. As of March 2024, about 7% of U.S. adults, roughly 17 million people, reported currently living with long COVID.
Here are the 12 hallmark symptoms, what’s happening in your body when they occur, and what each one actually feels like in daily life.
1. Post-Exertional Malaise
This is the most distinctive symptom of long COVID and carries the heaviest weight in the RECOVER scoring system. Post-exertional malaise (PEM) is a worsening of symptoms, or the appearance of entirely new ones, that hits up to 48 hours after physical or mental effort. It’s not ordinary tiredness. A grocery trip, a work meeting, or even a short walk can trigger a crash lasting days, weeks, or in some cases months.
The biological explanation centers on skeletal muscle. Long COVID is associated with mitochondrial dysfunction in muscle tissue, meaning cells struggle to produce energy efficiently. Your muscles shift toward a less efficient energy pathway, producing excess lactic acid during activity. Exercise can also trigger rapid muscle tissue damage and an influx of immune cells, compounding the fatigue. Critically, the threshold for triggering PEM varies from person to person and can change over time, making it unpredictable.
2. Fatigue
Fatigue in long COVID is separate from post-exertional malaise, though the two often overlap. This is a persistent, baseline exhaustion that doesn’t resolve with rest or sleep. In one large cohort of long COVID patients, 93% reported fatigue as a symptom. The same mitochondrial problems that drive PEM contribute here: when your cells can’t efficiently convert oxygen and nutrients into energy, everything from thinking to standing feels harder than it should.
3. Brain Fog
Brain fog covers difficulty concentrating, slowed thinking, trouble finding words, and problems with short-term memory. In long COVID cohorts, about 48% report concentration difficulties and 45% report memory loss. These aren’t subtle. Many people describe feeling like they’re thinking through mud.
The underlying cause involves persistent inflammation in the brain. Even after the virus clears, immune pathways remain activated, and inflammatory signals continue circulating. Research has found elevated levels of a specific immune signaling molecule (CCL11) in the brain’s memory center in people with cognitive symptoms after COVID. There’s also evidence of an autoimmune-like process where the body’s own antibodies infiltrate the central nervous system, damaging the protective coating around nerve fibers. Researchers have grouped brain fog with extreme fatigue and depression under the term “Brain FADE syndrome,” reflecting how these neurological symptoms tend to travel together.
4. Dizziness
About 46% of long COVID patients report dizziness, and for many it’s connected to a condition called postural orthostatic tachycardia syndrome (POTS). POTS causes your heart rate to jump by at least 30 beats per minute when you stand up, without a corresponding drop in blood pressure. In one study of highly symptomatic long COVID patients, 31% met the diagnostic criteria for POTS.
Even without a full POTS diagnosis, dizziness in long COVID can stem from autonomic nervous system dysfunction, where the part of your nervous system that automatically regulates blood pressure, heart rate, and digestion stops working smoothly. Standing up, being in warm environments, or skipping meals can all make it worse.
5. Heart Palpitations
Palpitations, the sensation that your heart is racing, pounding, or skipping beats, show up in 10% to 80% of long COVID patients depending on the study. That wide range partly reflects the high prevalence of both POTS and inappropriate sinus tachycardia (where the heart beats too fast at rest for no clear reason) in this population. In one large cohort, 60% reported palpitations.
Tiny blood clots may play a role. Research has identified abnormal fibrin microclots in the blood of long COVID patients, some measuring between 1 and 200 micrometers. These clots can block capillaries and restrict oxygen delivery to tissues, forcing the heart to work harder. Widespread inflammation of blood vessel walls (endotheliitis) compounds the problem.
6. Loss of or Change in Smell
Persistent loss of smell, or its distortion (where familiar things smell wrong or rotten), is one of the most recognizable long COVID symptoms. The reason some people never fully recover their sense of smell comes down to an ongoing immune attack inside the nose. Biopsies of the olfactory tissue in long COVID patients reveal T-cells actively inflaming the area where smell nerve cells live, even when no detectable virus remains. It resembles an autoimmune process. Over time, this chronic inflammation reduces the number of olfactory sensory neurons, which is why recovery can be slow or incomplete.
7. Loss of or Change in Taste
Taste changes often accompany smell loss since the two senses are deeply intertwined, but they can also occur independently. Some people experience a persistent metallic, bitter, or muted taste. The mechanism is similar: immune-driven inflammation damages the sensory cells responsible for detecting flavor. For many, taste recovers before smell does, but in a subset of patients, distortions can persist for months or longer.
8. Chronic Cough
About 41% of long COVID patients in clinical studies report a persistent cough. This isn’t residual mucus from the acute infection. In many cases, it reflects ongoing irritation and inflammation in the airways. The same microclots found in the bloodstream can obstruct tiny capillaries in the lungs, reducing oxygen exchange and contributing to the sensation of breathlessness that often accompanies the cough. During acute COVID, these fibrin deposits create the characteristic “ground-glass opacities” visible on CT scans, and in some long COVID patients, low-grade vascular damage in lung tissue persists well beyond the initial illness.
9. Shortness of Breath
Dyspnea, or shortness of breath, affects roughly 70% of long COVID patients in clinical cohorts. It can show up during mild exertion or even at rest. The microclot theory offers one explanation: when tiny clots block capillaries throughout the lungs, less surface area is available for oxygen to pass into the bloodstream. The result is a body running on reduced oxygen, which feels like air hunger even when your lungs are technically clear on imaging. Endothelial damage (injury to the cells lining blood vessels) compounds this by making oxygen exchange less efficient at the cellular level.
10. Chest Pain or Pressure
About 59% of long COVID patients report chest pressure or pain. This can feel like tightness, heaviness, or sharp stabbing sensations. It’s often linked to the cardiovascular and autonomic dysfunction described above. Inflammation of the blood vessel lining, microclot formation, and heightened nerve sensitivity can all contribute. For patients with POTS, chest pressure frequently worsens with standing or activity. The symptom understandably causes anxiety, which can create a feedback loop that makes the sensation feel more intense.
11. Gastrointestinal Symptoms
Long COVID GI symptoms include nausea, bloating, abdominal pain, diarrhea, and loss of appetite. These are linked to disruption of the gut microbiome. The virus triggers immune pathways and inflammatory signals that alter the balance of intestinal bacteria, a state called dysbiosis. This imbalance doesn’t just cause digestive problems. Research suggests gut dysbiosis in long COVID also contributes to neurological symptoms and fatigue, reflecting the well-established connection between gut health and brain function.
Early studies have explored probiotics and, in one small trial, fecal microbiota transplantation to restore normal intestinal flora, with some improvement in symptoms. Exercise and breathing-focused rehabilitation have also shown promise for GI-related long COVID symptoms.
12. Joint or Muscle Pain
Joint pain affects about 53% of long COVID patients in clinical studies, and muscle pain (sometimes accompanied by tingling or numbness, reported by 47%) rounds out the 12 signature symptoms. The same systemic inflammation and impaired oxygen delivery that affect other organs also target connective tissue and muscles. Autoimmune-like processes, where the immune system attacks the body’s own tissues, may play a role here as well. For some patients, this pain is constant; for others, it flares and recedes unpredictably.
How the PASC Score Works
The RECOVER researchers developed a scoring algorithm that weighs these 12 symptoms to generate an overall “PASC score” (post-acute sequelae of SARS-CoV-2). Not all symptoms carry equal weight. Post-exertional malaise and sensory changes like smell loss are weighted more heavily because they are more specific to long COVID, while symptoms like fatigue or joint pain, which overlap with many other conditions, carry less individual weight.
Importantly, this scoring system is a research and clinical tool, not a checklist you need to pass. The researchers themselves emphasize that someone with symptoms outside these 12 can still have long COVID and still deserves care. The score helps standardize research and improve diagnosis, but it doesn’t capture every way the condition can present.
What Reduces Your Risk
Vaccination significantly lowers the chance of developing long COVID. One study of over 500,000 adults found a 21% risk reduction after one dose, 59% after two doses, and 73% after three or more doses compared to unvaccinated individuals. A separate analysis found three doses provided up to 69% protection against long COVID in people without prior infection. Vaccination doesn’t eliminate the risk entirely, but it’s the strongest preventive factor identified so far.