Relapse

A relapse in myalgic encephalomyelitis/chronic fatigue syndrome is.

NHS definition
The UK's National Health Service definition of a relapse can be found within the 2021 NICE guidelines.

International Consensus Criteria
The International Consensus Criteria does not define what a relapse is, but states that relapses can last for days, weeks or longer.

Impact
The impact of a relapse varies from person to person. But most will find that they will have to revisit any coping mechanisms they have used prior to relapse to manage symptoms or avoid triggers. Energy levels will be heavily depleted and it is likely to take several weeks if not months or longer to return to pre-relapse levels.

Similarly, with symptoms it will take a long time for them to ease, and this in turn goes to aggravate energy levels.