What to explain
What changed after the illness?
Since [infection and date], I have had [thinking problems] and can no longer manage [specific tasks] as before. I want to discuss Long COVID, whether I meet ME/CFS criteria, and other treatable causes. I have noticed [describe any worsening after activity, its timing and duration, or say that you have not noticed this].
Questions to take in
Questions about diagnosis, testing and care
- Does my history meet the definition of Long COVID, the criteria for ME/CFS, both, or neither?
- Which condition could explain each major symptom, and which blood, sleep, heart, lung, neurological, or standing test has a clear reason in my case?
- Do my dizziness, racing heart, weakness, or worse thinking while upright need lying and standing blood pressure and heart rate, an active stand test, or a tilt table test?
- Could my brain fog come partly from anemia, iron levels, thyroid disease, low B12, blood sugar, sleep apnea, migraine, a medicine, depression, anxiety, heart disease, or lung disease?
- Do I have post-exertional malaise, and what amount of physical and mental activity is least likely to make my symptoms worse?
- Should exercise testing be avoided because it may cause a serious symptom flare, or is there a specific medical reason to do it under supervision?
- Would occupational therapy, speech or cognitive rehabilitation, sleep care, autonomic care, respiratory care, or another symptom-based service help with a specific problem?
- What should be written in my record for work, school, disability, driving, mobility, or care accommodations?
Choosing useful checks
Tests guided by symptoms and examination
No test diagnoses Long COVID or ME/CFS. A CBC, CMP, thyroid, vitamin B12, ferritin, glucose, sleep, standing, thinking, or medicine check can identify a treatable problem or record a specific limitation. Not everyone needs every check.
CBC and CMP when symptoms or history warrant blood counts and metabolic checks
Checks blood cells, anemia, electrolytes, glucose, kidney and liver results. The clinician may add inflammation or infection tests when symptoms give a reason.
Ask your doctorTSH, B12 and ferritin when symptoms or history suggest a thyroid problem or deficiency
Checks thyroid function, vitamin B12, and stored iron. Abnormal results can cause fatigue or thinking trouble and need their own treatment plan.
Read the test guideHbA1c when blood sugar assessment is indicated
Estimates average glucose over about two to three months. Anemia, transfusion, pregnancy, kidney disease, or red-cell medicines can change what the result means.
Read the test guideLying and standing vital signs or an active stand test for symptoms while upright
This test records heart rate, blood pressure, and symptoms while you lie down and stand. If severe symptoms start, stop. Have it supervised if fainting or a serious heart problem is possible.
Ask your doctorSleep study when symptoms suggest sleep apnea or another sleep disorder
Checks sleep apnea and sleep movement or breathing problems. Unrefreshing sleep can still occur in ME/CFS when a sleep study does not find apnea.
Read the test guideCognitive assessment to document thinking difficulties
Records which thinking tasks are difficult and can support rehabilitation or accommodations. One score can't diagnose the cause of brain fog.
Ask your doctorMedication review for possible effects on thinking, sleep or fatigue
Checks whether a prescription, over-the-counter medicine, supplement, stimulant, sleep aid, antihistamine, or pain medicine could be adding to the symptoms.
Read the test guideBefore the appointment
Bring dates, results, medicines and activity notes
Bring a dated list of suspected or confirmed COVID infections and other infections. Include positive tests if you have them, but do not worry if testing was unavailable or negative.
Write what you could do before the illness and what you can do now. Use real examples from work, school, reading, driving, shopping, showering, cooking, childcare, exercise, and social time.
If you can, keep brief notes on demanding activities and how you feel later that day and over the next two days. Bring the notes you have; do not delay an appointment or cause a crash to complete a diary.
List the symptoms that become worse together, such as brain fog, heavy fatigue, pain, sore throat, headache, poor sleep, dizziness, racing heart, breathlessness, or sound and light sensitivity.
Bring prior blood tests, heart or lung tests, scans, sleep results, and visit notes from before and after the infection. Dates matter.
Bring every prescription, over-the-counter medicine, supplement, inhaler, stimulant, sleep aid, antihistamine, and pain medicine. Include timing and what changed after starting it.
If you already measure heart rate, blood pressure, oxygen, temperature, sleep, or steps, bring a short dated summary. Skip repeated testing or exercise done just to produce data.
Bring forms or a short list of the work, school, driving, mobility, or care tasks that now need an adjustment.
For each flare, write the activity, when symptoms became worse, and how many hours or days recovery took. Do not trigger a flare on purpose.
How the doctor assesses this
Details that may meet Long COVID or ME/CFS criteria
- Brain fog and other symptoms began or became worse after confirmed or suspected COVID or another infection.
- Physical, mental, emotional, or social activity makes several symptoms worse later, and recovery takes longer than it used to.
- There is a lasting drop in work, school, self-care, mobility, household, or social activity, with unrefreshing sleep, thinking trouble, or worse symptoms while upright.
Details that mean another cause or condition needs checking
- The brain fog was present before the infection and did not become worse or change after it.
- There is no lasting change in function and symptoms keep improving as expected after the short recovery period from an infection.
- There is no delayed worsening after activity. This weighs against ME/CFS but does not rule out Long COVID.
- Sleep apnea, anemia, low iron, thyroid disease, vitamin B12 deficiency, diabetes, a medicine, migraine, depression, anxiety, heart disease, lung disease, or another diagnosis explains the symptoms and timing better.
- A normal blood test does not rule out Long COVID or ME/CFS. It can still weaken a specific explanation such as anemia, low iron, thyroid disease, or diabetes.
What to understand before choosing care
How the clinician assesses the symptoms
- Long COVID and ME/CFS are clinical diagnoses. There is no blood test or scan that can prove or rule out either condition.
- Long COVID and ME/CFS are not the same diagnosis. Some people meet the criteria for both, while some people with Long COVID do not have post-exertional malaise.
- Post-exertional malaise is more than feeling tired after exercise. Several symptoms worsen after physical, mental, emotional, or social activity that did not cause problems before; the worsening is often delayed.
- Normal routine results do not mean the symptoms are not real. Blood tests, sleep testing, heart and blood pressure checks, and medicine review are used to find treatable conditions or complications.
- A safe activity plan depends on whether post-exertional malaise is present. Fixed increases in exercise can worsen ME/CFS, and NICE says they should not be used.
What the research found
What recent studies found
A 2025 review included 36 studies of cognition after COVID-19. Attention, memory, executive function, and processing speed were the areas most often affected.
The 36 studies used different Long COVID definitions, thinking tests, infection periods, and follow-up times. The review cannot tell one person which symptom will last or which treatment will work.
A 2025 review of ten community studies with 4,076 adults estimated that 25% had post-exertional malaise. The authors rated the evidence as low certainty because definitions and measurement methods differed.
The 25% estimate means post-exertional malaise is important but not present in everyone with Long COVID. It is not a personal forecast and should not be used to diagnose ME/CFS by itself.
A 2026 observational study followed 260 people for about 4.4 years. Mild cognitive impairment was diagnosed in 27% of the Long COVID group, 5% of the recovered-COVID group, and 1% of the COVID-negative group.
The 2026 percentages came from one observational cohort. Mild cognitive impairment is a clinical diagnosis, not another name for ordinary brain fog. The study does not tell us whether COVID caused each diagnosis.
A 2026 clinic study followed 150 adults with Long COVID and neurological symptoms. Average fatigue, physical function, social function, and pain scores improved over six months of mixed symptom-based care.
The clinic study had no untreated comparison group, and people received different combinations of education, rehabilitation, and medicines. It does not tell us which part led to improvement or whether the same changes would have happened without the clinic care.
Age, pregnancy and support needs
Children and teenagers can develop Long COVID or ME/CFS. The assessment should include school attendance, concentration, growth, sleep, standing symptoms, sports, friendships, and the support needed to keep learning without causing worse symptoms.
NICE says ME/CFS can be suspected after four weeks of required symptoms in children and young people. It can be diagnosed after three months when another condition does not explain them. US services may use different criteria.
Pregnancy and the months after birth can change heart rate, blood pressure, sleep, clot risk, iron, thyroid function, and energy. Coordinate symptom and medicine decisions with the maternity team.
Older adults need careful checks for medication effects, anemia, infection, heart or lung disease, sleep disorders, stroke, hearing or vision loss, and changes after intensive care. Check a new thinking problem before blaming normal aging or Long COVID.
Long COVID and ME/CFS occur in women and men. Sex does not confirm or rule out either condition, and there is no separate brain-fog cutoff based only on sex.
A person who looks well during a short visit may still have a large loss of function or symptoms that worsen after the appointment. Ask for rest, shorter visits, written instructions, remote care, or a support person when needed.
If the answer is no
If your doctor says normal tests rule out Long COVID
No single lab test or scan confirms or rules out Long COVID. CDC says clinicians can diagnose it from your history and a physical exam, and order specific tests when a symptom or another possible diagnosis needs checking.
What changes the answer
- Bring the infection and symptom timeline. Record known or suspected COVID illness, the symptoms that followed, periods of improvement and the activities that now trigger worsening.
- Describe function in concrete terms. Explain what changed in work, study, self-care, exercise tolerance and recovery after physical or mental effort. Normal routine tests do not erase those changes.
- Ask which alternatives still need checking. Targeted tests may make sense for a specific heart, lung, neurological, hormone or sleep concern, but not as a general Long COVID panel.
- Request symptom-based care and follow-up. Ask what's treatable now, how post-exertional worsening will be taken into account, and which new findings should lead to specialist assessment.
United States, United Kingdom, and Australia
Getting care
US United States
Bring the infection, symptom, activity, result, and medicine timeline. Primary care can check urgent problems and common causes, document the criteria, and refer for sleep, heart, lung, neurological, standing, or rehabilitation care.
- CDC says Long COVID can be diagnosed from the history and examination. A positive COVID test is not required, and no laboratory test can prove or rule out the condition.
- The 2024 National Academies definition describes Long COVID as a condition after SARS-CoV-2 infection that lasts at least three months. It can be continuous, come and go, or become worse over time.
- CDC uses the Institute of Medicine ME/CFS criteria, including more than six months of reduced function. Ask the clinician to record the functional loss, post-exertional malaise, sleep, thinking, and standing symptoms.
UK United Kingdom
Ask the GP which symptoms need testing and which service can help. The GP can arrange blood, heart, lung, sleep, or standing checks, record the effect on daily life, and refer when symptoms are severe, unusual, or not improving.
- NICE calls symptoms from four to twelve weeks ongoing symptomatic COVID-19 and symptoms beyond twelve weeks post-COVID-19 syndrome when another diagnosis does not explain them.
- The GP assessment should cover physical symptoms, thinking, mental health, daily function, and the effect on work or education. New cognitive symptoms can be recorded with a validated screening tool.
- NICE NG206 says fixed increases in exercise should not be used for ME/CFS. NICE also says its ME/CFS evidence review didn't study COVID-19, so the whole guideline shouldn't be applied automatically to every person with Long COVID.
AU Australia
Ask for tests and referrals that match the symptoms. The GP can check common causes, decide whether standing or exercise testing is safe, document daily limitations, and use local referral options for the symptoms causing the most trouble.
- Healthdirect says there is no single test for Long COVID. A GP may choose blood tests, blood pressure and heart rate checks, lung tests, an ECG, an X-ray, or an exercise test based on the symptoms.
- Exercise testing is not automatically safe for someone with post-exertional malaise. Tell the clinician about delayed symptom flares before a sit-to-stand, walking, or exercise test.
- Long COVID programs and clinics differ by state and region. A GP can refer to available rehabilitation or to a heart, lung, sleep, neurological, or other service for a specific problem.
Safety
Show how it affects daily life
- Conversation and screens count as effort too. Notice how much activity sets off symptoms, and whether they're worse over the next two days.
- Use one ordinary task, such as reading one page or preparing a simple meal, to describe what now becomes difficult. Describe what happens during ordinary activity; do not repeat a task to provoke symptoms.
- Break necessary activity into smaller parts, sit for tasks when helpful, and place rest before and after demanding activity. This may reduce symptom flares but is not a cure.
- Keep meals, fluids, medicines, and sleep as steady as is safe for you. Ask before increasing salt or fluid if you have kidney, heart, blood pressure, or pregnancy concerns.
- Use lists, alarms, written instructions, fewer open tabs, and quiet work blocks to reduce memory load. Record whether the change helps a specific task.
- If a new plan keeps making brain fog, pain, dizziness, breathlessness, or fatigue worse later that day or over the next two days, stop and get advice.
Source checked
Sources behind this handout.
- 01
Centers for Disease Control and Prevention. Long COVID Clinical Guidance. Updated March 9, 2026.
Source - 02
Centers for Disease Control and Prevention. Evaluation of ME/CFS. Updated April 17, 2026.
Source - 03
Centers for Disease Control and Prevention. Fast Facts: ME/CFS.
Source - 04
National Academies of Sciences, Engineering, and Medicine. A Long COVID Definition. 2024.
Source - 05
NICE. COVID-19 Rapid Guideline: Managing the Long-Term Effects of COVID-19. NG188.
Source - 06
NICE. ME/CFS: Diagnosis and Management. NG206.
Source - 07
Healthdirect Australia. Long COVID. Reviewed September 2025.
Source - 08
Panagea E et al. Neurocognitive Impairment in Long COVID: A Systematic Review. Arch Clin Neuropsychol. 2025;40:125-149. PMID 38850628.
Source - 09
Pouliopoulou DV et al. Prevalence and Impact of Postexertional Malaise on Recovery in Adults With Post-COVID-19 Condition. Arch Phys Med Rehabil. 2025;106:1267-1278. PMID 39921187.
Source - 10
Frontera JA et al. Increased Incidence of Mild Cognitive Impairment in Long COVID Patients. Alzheimers Dement. 2026;22:e71237. PMID 41772376.
Source - 11
Friedberg A et al. Outcomes of Patients With Neurocognitive Symptoms Attending a Long COVID Clinic. J Gen Intern Med. 2026. PMID 41857445.
Source