Fibromyalgia is a syndrome (a group of symptoms signifying a diseased state) not a standard disease. It doesn't show in blood tests rly at all

Fibro is often used as what they call a "wastebasket disease." It, along with CFS/ME (chronic fatigue syndrome) are generally thought of to have a cause of some sort, but it's as-of-yet poorly understood, and there are no widely-used diagnostic tests. So, what they do is they rule out other causes for your symptoms, then they diagnose you based on self-reported symptom severity. This process is thankfully happening faster now than it used to, in large part because as the disease is better understood, the medical community is coming to realize fibromyalgia is often comorbid with other syndromes and diseases. Much like how someone with Parkinson's is more likely to have depression, someone with an autoimmune disease or many other pain diseases and mental health problems is more likely to have fibro. To my understanding, fibro has to do with your brain's ability to "calm down" your nerves. It's been explained to me by pain therapists as "PTSD of the body." When you're having a fibro flare, your nerves have no chill. This can manifest as a pretty wide number of issues. You've got sensory neurons and motor neurons, so different problems can come up and make it tricky to diagnose. Sensory neurons will cause widespread pain and increased pain sensitivity, as well as loss of sensation and bizarre sensations such as having wet feet when they're dry. Motor neurons can mean muscle spasms, bouts of muscle weakness, and issues like IBS and TMJ dysfunction. The only things that really seem consistent between most folks with fibro are pain in multiple sites, fatigue, and something else which interferes with their life, be it IBS, or something mental like brain fog, depression or anxiety. Honestly, most folks battling chronic illness could meet the diagnostic criteria for fibro. If they don't find one of those, you've got fibro.

Fibromyalgia is a diagnosis of exclusion. No definitive testing is available. The cause of pain is unknown, and besides treating the pain itself, looking at different perspectives, like psych, endocrine, neuro, etc. may yield positive results and lessen the pain.

My blood tests showed high inflammation, but it took me having to start a symptom journal to actually get diagnosed with fibromyalgia.