What is malaise syndrome and can it be diagnosed with a blood test?

Malaise syndrome. There is no blood test for malaise syndrome. Malaise is a general term to mean "feeling unwell." although somewhat controversial, chronic fatigue syndrome is said to be associated with post-exertional malaise such as fatigue, light-headedness, muscle or joint pain, cognitive dysfunction, headache, nausea, weakness, trembling or insomnia.
??? Perhaps you are referring to chronic fatigue syndrome? To my knowledge, there are no lab tests that can diagnose it. It's a clinical diagnosis.
Diagnosis to bill. Labs need a diagnosis in order to bill for t.
Fatigue . Another word for fatigue. Work up includes a detailed history, physical exam an some labs. Please see your phsician.