What can cause my platelets, white blood cells and red blood cells are all high causing leukocytosis, mild thrombocytosis and macrocytes?

Inflammation . Macrocytes are white blood cells too. Also depends how high they are. Very mild elevation like 10-13 for WBC and 400-450 for platelets could be lab variations too. If mild to moderate suggests inflammation which can be from infection, autoimmune disorders. If very high, blood disorders are a concern. Whomever ordered the test should follow up with u.