Idiopathic Parkinson’s disease
Impulsive personality disorder
In-patient department
Inter-pupillary distance, the distance between the center of the pupils of the two eyes
Invasive pneumococcal disease

Organizations

Initiative for Policy Dialogue, an organization based at Columbia University
Chartered Institute of Personnel and Development, a professional association for human resource management professionals

Police departments

Indianapolis Police Department, former police department of Indianapolis and preceding agency of the Indianapolis Metropolitan Police Department
Independence Police Department (Missouri), police department of Independence, Missouri
Inglewood Police Department, Inglewood, California
Irvington Police Department (NJ), police department of Irvington, New Jersey