10/02/2026
Saw this posted in a group im in and, as ive been pretty much bedbound and mostly asleep since Friday afternoon after having the audacity to do some fun things last week, it felt like a good idea to share. I know people in my life dont understand PEM or PENE so this may help. I shall now be medicating then going back to sleep 😴
From Dr Groysman:
You cannot have ME/CFS without PEM. Period.
This gets misunderstood all the time.
Post-exertional malaise (PEM) is not optional in ME/CFS.
It is the defining feature in every modern diagnostic criteria.
No PEM = not ME/CFS.
That does not mean someone is “fine” or that their fatigue is imaginary.
You can have severe, life-altering fatigue without PEM.
It just means the diagnosis is something else.
PEM is not:
• Feeling tired during activity
• Being sore after exercise
• Needing a nap
PEM is:
• Delayed symptom worsening (often 12–48 hours later)
• Multi-system crashes (brain fog, pain, flu-like symptoms, autonomic instability)
• Prolonged recovery
• Loss of baseline after overexertion
This distinction matters because:
• ME/CFS management is crash prevention and pacing
• Many Long COVID patients do not have PEM and are more treatable
• PEM often marks the transition from a reversible condition to a fixed disease state
Long COVID can exist without PEM.
ME/CFS cannot.
If PEM is present, prognosis, treatment strategy, and risk profile all change.
Understanding this is not gatekeeping.
It is how we avoid misdiagnosis and missed treatment opportunities. This is also why it it is important not to lump everything into ME/CFS!
