How often does a human being need a regular checkup at the doctor? What does this checkup include?

once or twice a year chickup at least and go to see the doctor

Actually it varies from patient to patient. If I consider a normal human being for regular medical checkup then , According to American medical association every individual( 18 y -40 years )  should go  for periodic  medical checkup every 5 year interval and above 40 years should go for checkup 1-3 years interval based on their health condition.

Though Previously American Medical Association recommend everyone go for annual medical checkup. 

There are several Types of Check up includes , 

1. Preventive care 

- Primary prevention  like , Immunization against certain diseases ( measles ) 

- Secondary prevention , Includes reducing risk factor for that regular checkup of blood pressure ,  sugar level , cholesterol level .

-Tertiary prevention includes management of Heart disease. 

2. Doctor might suggest for different screening test including blood pressure reading , pap test for screening cervical cancer. 

-If there is any specific reason doctor might recommend, ECG, Routine Urine analysis , screening for prostate and ovarian cancer  . 

If anyone wants to know further information regarding medical checkup , I will recommend them to  explore following reference  

- American Academy of Family Physicians. Summary of AAFP recommendations for periodic health examinations. 2001. Summary of AAFP recommendations for periodic health examinations.

- Centers for Disease Control and Prevention. National Center for Health Statistics. 2001. National Center for Health Statistics.

- U.S. Preventive Services Task Force. Guide to Clinical Preventive Services