Summary
The 2026 American Academy of Pediatrics and NASPGHAN clinical practice guideline replaces the term failure to thrive with faltering weight and, for the first time, gives the diagnosis a standardized z-score-based definition drawn from data already in the electronic health record [1]. Faltering weight occurs in roughly 5% to 10% of children in primary care and is a growth pattern that requires explanation, not a diagnosis in itself [1].
- The guideline changed the term deliberately. Failure to thrive was descriptive, had no precise definition, and carried negative connotations for families, so the panel adopted faltering weight to align with the 2017 NICE terminology [1].
- The definition moved from percentiles to z-scores. Faltering weight is met by any one of three criteria measured against a growth standard, using the World Health Organization standard from birth to two years [1][3].
- Most faltering weight is driven by inadequate caloric intake rather than occult organic disease, and the history and examination identify the cause more often than laboratory screening does [1][2].
- The guideline recommends against routine diagnostic testing in a child without specific signs or symptoms, and against using socioeconomic status as an assigned risk factor [1].
Caution. Correct the growth reference for prematurity and for known syndromic growth patterns before applying the z-score criteria. Accurate anthropometric measurement is the foundation of the diagnosis, because an error in length or in plotting produces a false z-score in either direction [1].
Diagnosis
The guideline defines faltering weight by any one of three z-score criteria rather than a single percentile cutoff [1].
| Criterion |
Threshold |
| Weight-for-length or BMI-for-age |
< −1.65 z score (5th percentile) [1] |
| Weight gain velocity, age < 2 years |
< −2 z score for age (2.3rd percentile) [1] |
| Decline across measurements |
Fall in weight, weight-for-length, or BMI ≥ 1 z score [1] |
The third criterion is the longitudinal one, and it captures the child who is losing ground over serial visits even when a single measurement is not yet below a cutoff [1][2]. Serial plotting on an accurate growth chart is what makes that decline visible, so establish the trajectory before ordering anything.
Plot weight, length, and head circumference from birth to 24 months in WHO Growth →
Plot growth for children 2 years and older in CDC Growth →
Distinguish a child who is small but tracking a consistent centile from one whose growth velocity has fallen below the age-specific threshold. A calculated interval growth velocity operationalizes the second criterion in children under two years.
Calculate interval growth velocity in Growth Velocity →
Set the trajectory against the child's genetic potential. A child tracking toward the mid-parental target is different from one falling away from it.
Estimate genetic target height in Mid-Parental Height →
Evaluation
The guideline is explicit that a broad workup is not the default. In a child without specific signs, symptoms, or findings that would prompt a focal evaluation, the panel recommends against diagnostic testing as part of the initial routine workup, because its yield is low and it adds cost and burden without changing management [1]. Testing is directed by the history and examination, not ordered as an undifferentiated panel [1][2].
Endoscopy has a similarly narrow role. The panel does not recommend endoscopy in the initial workup, reserving endoscopy with biopsy for children with persistent faltering weight or a specific concern for a condition that cannot be diagnosed otherwise [1].
The guideline also recommends against using socioeconomic status as an assigned risk factor when diagnosing faltering weight [1]. Poverty and food insecurity remain relevant to a child's nutrition and are worth addressing, but they should not be treated as a diagnostic risk marker that biases the evaluation.
Management
Diagnosing faltering weight is the first step toward deciding whether the child has malnutrition, needs increased energy provision, or requires further testing [1]. The first-line intervention in most children is increasing caloric intake, and the guideline recommends oral nutritional supplementation to deliver those additional calories [1]. This often means increasing the caloric density of foods the child already accepts rather than simply adding volume [1][2].
When a documented feeding difficulty is present, the guideline recommends therapy for pediatric feeding disorder, since a mechanical or behavioral feeding problem will not resolve with added calories alone [1]. Management is multidisciplinary and can involve dietitians, feeding and speech therapists, lactation consultants, and social workers alongside the primary clinician [1].
Follow-up is the treatment. Frequent weight checks on the same scale confirm the response to increased intake and separate the child who recovers with feeding support from the smaller group who need further evaluation [1][2].
References
- Kersten HB, Goday PS, Abdelhadi R, et al; American Academy of Pediatrics and North American Society for Pediatric Gastroenterology, Hepatology and Nutrition. Clinical practice guideline for diagnosis and management of faltering weight. Pediatrics. 2026;157(4):e2025075764. doi:10.1542/peds.2025-075764
- Shields B, Wacogne I, Wright CM. Weight faltering and failure to thrive in infancy and early childhood. BMJ. 2012;345:e5931. doi:10.1136/bmj.e5931
- de Onis M, Onyango AW, Borghi E, et al. WHO Child Growth Standards based on length/height, weight and age. Acta Paediatr. 2006;95(S450):76-85. doi:10.1111/j.1651-2227.2006.tb02378.x