I am always feel v tired I don't know why I had blood test sll is fine?

Fatigue. Blood work ordered for fatigue look for anemia, infections, inflammatory arthritis, endocrine disorders(like diabetes and hypothyroidism) and liver or kidney dysfunction. Causes for fatigue not always screened by blood work include depression, sleep disorders (like sleep apnea), heart disease , pulmonary disorders and chronic fatigue. A good history will help you and your doctor.