Failure to thrive (FTT), more recently known as faltering weight or weight faltering, is a term used in pediatric, adult as well as veterinary medicine, (where it is also referred to as ill thrift) to indicate insufficient weight gain or inappropriate weight loss.
When not more precisely defined, the term refers to pediatric patients. In MeSH, the term is assumed to refer to an infant or child. In children, it is usually defined in terms of weight, and can be evaluated either by a low weight for the child's age, or by a low rate of increase in the weight.
As used by pediatricians, it covers poor physical growth of any cause and does not imply abnormal intellectual, social, or emotional development, although of course it can subsequently be a cause of such pathologies. The term has been used in different ways, and different objective standards have been defined. Many definitions use the 5th percentile as a cutoff.
Traditionally, causes of FTT have been divided into endogenous and exogenous causes. Initial investigation should consider physical causes, calorie intake and psychosocial assessment.
Caused by caregiver's actions. Examples include physical inability to produce enough breastmilk, using only babies' cues to regulate breastfeeding so as to not offer a sufficient numbers of feeds (sleepy baby syndrome), inability to procure formula when needed, purposely limiting total caloric intake (often for what the caregiver views as a more aesthetically pleasing child), and not offering sufficient age-appropriate solid foods for babies and toddlers over the age of six months.
However, to think of the terms as dichotomous can be misleading, since both endogenous and exogenous factors may co-exist. For instance a child who is not getting sufficient nutrition may act content so that caregivers do not offer feedings of sufficient frequency or volume, and a child with severe acid reflux who appears to be in pain while eating may make a caregiver hesitant to offer sufficient feedings.
Recently the term faltering growth has become a popular replacement for failure to thrive, which in the minds of some represents a more euphemistic term.
The term "failure to thrive" is also applied to geriatrics, or more generally in adult medicine.
In adult medicine, failure to thrive is a descriptive, non-specific term that encompasses "not doing well": e.g., malaise, weight loss, poor self-care that can be seen in elderly individuals.