Failure to thrive (FTT): Refers to a child whose physical growth is significantly less than that of peers.

There is no official consensus on what constitutes failure to thrive (FTT). It usually refers to a child whose growth is below the 3rd or 5th percentiles for their age or whose growth has fallen off precipitously and crossed two major growth percentiles (for example, from above the 75th percentile to below the 25th percentile).

Failure to thrive in early infancy sometimes results in death, and in older infancy or childhood is an important marker for underlying disease. Causes of failure to thrive are probably many, including unrecognized food allergies leading to refusal of food and vomiting, undiagnosed metabolic disorders, and disease.

A specific type of failure to thrive is sometimes seen in abandoned or institutionalized infants who seem to "give up" and become listless and unwilling to nurse. It is assumed that this phenomenon is emotional in nature, although other factors may also be at work.

Treatment of failure to thrive requires discovering and treating its underlying cause(s). In the interim, IV feeding is required some cases, while in others supplemental high-calorie feedings can help.