‘Faltering Weight’ Is the New Term for ‘Failure To Thrive’: What This Means for Your Patients

The term “failure to thrive” has been in the medical lexicon since the 1930s, and some iterations of the term date back even further. In modern medicine, it’s been regarded as an antiquated, even pejorative, term but it was still used for purposes of diagnosis and coding—until now.

The American Academy of Pediatrics (AAP) and the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) published a new clinical practice guideline (CPG) in March 2026 that recommends and defines faltering weight, replacing failure to thrive.

In addition to the negative connotation of failure to thrive, the term’s ambiguity and the lack of clear clinical guidance invite subjectivity and interpretation among clinicians.

Unified terminology

Senthilkumar Sankararaman, MD, Co-Director of the Pediatric Advanced Nutrition Program at Cleveland Clinic Children’s, says unified terminology is a major advantage. “Previously, it was more difficult to evaluate the burden of disease. For example, I might code as ‘poor weight gain’ while a colleague might say ‘failure to thrive’ and another will say ‘growth faltering.’”

The implications of this are far-reaching. Not having a universal definition can impact everything from a delay in addressing the underlying etiological reasons and inconsistent management approach in getting the essential nutrition to patients, and more.

New diagnostic criteria

The new CPG also aims to standardize diagnostic criteria for faltering weight using z-score cutoffs, rather than percentiles. “Historical definitions included weight-for-age below the fifth or third percentile or children crossing two major percentile lines,” explains Dr. Sankararaman.

The new guideline includes the following definitions:

• Weight-for-length or BMI-for-age less than –1.65 z-score (fifth percentile)
• For children younger than 2, weight gain velocity less than –2 z-score for age (2.3^rd percentile)
• Decline in weight, weight-for-length or a BMI greater than or equal to 1 z-score

In other words, Dr. Sankararaman says clinicians now have more objective data points to make a faltering weight diagnosis and closely monitor health status in response to interventions.

“In the new classification, dropping one z-score—instead of waiting until they reach the third or fifth percentile or until they drop two major percentiles— is enough to diagnose them with faltering weight.”

Observing improving or declining z-scores also helps clinicians evaluate whether interventions are working or not. “We have seen kids with –4 or –5 z-scores who we are able to follow and evaluate when z scores are improving and whether they are responding to the intervention,” he says. This is pragmatically easier and advantageous than focusing just on percentiles.

When to consider endoscopy

The guideline, published jointly by AAP and NASPGHAN, also provides an update on the use of endoscopy in a diagnostic workup.

“Most patients with faltering weight do not require rigorous diagnostic testing,” explains Dr. Sankararaman. He says that a thorough patient history, including birth and developmental history, family and social factors, dietary history, and clinical exam often provides enough compelling evidence for pediatricians to decipher the underlying cause.

However, upper endoscopy should be considered in cases with no clear explanation, no meaningful improvement or when chronic gastrointestinal symptoms are present, particularly alongside an atopic history. In these cases, pediatricians should consider referring to a specialist to confirm a differential diagnosis of eosinophilic esophagitis or celiac disease, if prompted by a serological test.

“Once we confirm these conditions, the management drastically changes, and, often, we see improved growth and feeding outcomes,” concludes Dr. Sankararaman.