There is no test for ME/CFS, so the diagnosis is made by elimination

There is no test available to specifically screen for ME/CFS.

That single fact shapes everything about how myalgic encephalomyelitis /
chronic fatigue syndrome is diagnosed. **Blood and urine samples are taken to
rule other illnesses out**, not to find this one, and a physical and mental
exam is done for the same reason. What is left is **your symptoms and health
history** — which makes the interview the diagnostic instrument.

The questions that are actually about ME/CFS

The basic history — other diagnoses, medications, prior illnesses and
surgeries, allergies, family illness — is the same anywhere. The ME/CFS
questions are about function, and they are worth reading in advance:

• What can you do now? How is it different from before?
• How long have you felt this way?
• Do you feel better after sleeping or resting?
• What makes you feel worse? What helps you feel better?
• What happens when you push to do activities that are now hard for you?
• Are you able to think as clearly as you did before becoming ill?
• What symptoms keep you from doing what you need or want to do?

Two of those are doing particular work. Do you feel better after resting and
what happens when you push are asking about the pattern that distinguishes
this illness from ordinary tiredness — the crash that follows exertion, rather
than the recovery that follows rest.

Why an activity journal helps

**You may want to keep an activity journal. This could help you remember
important details when you see a healthcare provider.**

The answers above are hard to reconstruct from memory in a short appointment,
and they are the evidence. A written record of what you did and what happened
afterwards is not a supplement to the diagnosis — with no test to fall back
on, it is a substantial part of it.

Specialists rule things in as well as out

A referral may go to **a neurologist, a rheumatologist, or a sleep
specialist**. They check for other conditions that cause similar symptoms
— and **may find conditions that can be treated, either instead of or in
addition to ME/CFS.** Treating those may help you feel better regardless of
where the main diagnosis lands.

The 2015 Institute of Medicine report on ME/CFS sets out the symptoms
required for the diagnosis, and those that some people with ME/CFS have and
others do not.

Source: Centers for Disease Control and Prevention.