Faltering Weight: What the New AAP Guideline Means for Your Practice

There are few things in pediatrics that can make an otherwise routine well-child visit feel complicated quite as quickly as a growth chart.

The weight is down. Or maybe it hasn’t moved much. A percentile has been crossed. A parent is worried. You’re wondering: Does this child need more calories? More testing? A GI referral? Or maybe just a little more time.

For years, pediatricians called this “failure to thrive,” a term that has been both imprecise and, for families, pretty unsettling. Now we have a new framework.

In 2026, the American Academy of Pediatrics (AAP), in collaboration with the North American Society for Pediatric Gastroenterology, Hepatology & Nutrition (NASPGHAN), released a new clinical practice guideline on the diagnosis and management of faltering weight¹ in children ages 0 to 5 years. The guideline provides clinicians with clearer diagnostic criteria, shifts the focus from percentiles to z-scores, and offers a more structured approach to evaluation and treatment.

And perhaps one of the most useful messages is this: Not every child with faltering weight needs a giant laboratory workup.

So what does the new guideline mean for those of us in clinic?

What is Faltering Weight?

The change in terminology isn’t just semantics.

“Failure to thrive” never had one precise definition, which meant clinicians could use the term differently and approach evaluation and follow-up differently. It also carries a negative connotation that can land pretty hard with parents.

The older framework also tended to divide cases into “organic” and “non-organic” causes. In reality, those categories overlap considerably. Feeding behavior, medical conditions, nutrition, development, and a family’s circumstances don’t always fit neatly into separate boxes.

Faltering weight gives us a more descriptive — and less loaded — way to talk about what we’re actually seeing: a concerning change in a child’s growth trajectory. It names the poor weight gain without assuming a cause.

Z-Scores instead of percentiles

For many clinicians, this may be the biggest adjustment in the guideline.

We’re accustomed to talking about growth in percentiles: “She’s at the 3rd percentile for weight,” or “He dropped from the 50th to the 15th.”

The new guideline emphasizes z-scores instead.

A z-score describes how far a measurement falls from the population mean. A z-score of 0 corresponds to the 50th percentile, while a z-score of -2 corresponds to roughly the 2.3rd percentile.

Why bother changing?

Because z-scores remain useful at the extremes of the growth chart. Percentiles get increasingly difficult to interpret when a child falls below the 1st percentile, while z-scores can continue to quantify changes. That makes it easier to see whether a child at the low end of the chart is improving, remaining stable, or continuing to fall.

Fortunately, you don’t necessarily need to calculate this yourself. Tools such as PediTools can calculate pediatric growth z-scores, and this is also a great opportunity to advocate for automatically displaying z-scores in your EHR.

How is faltering weight diagnosed?

The guideline's diagnostic criteria rest on three z-score cutoffs. A child may meet criteria for faltering weight with any one of the following:

• Weight-for-length or BMI-for-age below a z-score of -1.65, corresponding to the 5th percentile

• In children younger than 2 years, weight-gain velocity below a z-score of -2.00 for age

• A decline in weight, weight-for-length, or BMI that drops at least 1.00 z-score

But, and this is an important but, meeting one criterion does not automatically mean a child is undernourished or unhealthy.

A large-for-gestational-age infant may naturally settle onto a lower growth trajectory after birth. A child who was born small may remain small while otherwise growing appropriately.

The growth chart is telling you that something deserves a closer look. It doesn’t tell you what that something is.

Before Ordering Labs, Ask Better Questions

Here’s where the guideline may save clinicians — and families — from unnecessary testing.

For children with faltering weight, the AAP recommends against routine diagnostic testing as part of the initial workup when there are no specific signs, symptoms, or examination findings pointing toward an underlying condition. Instead, the initial evaluation should include a thorough history and physical examination, developmental evaluation, family and social history, medical and surgical history, and a detailed assessment of growth and feeding.

In other words, our first diagnostic tools are ones we already have: a good history and physical.

What Should You Ask About Feeding?

Feeding history deserves particular attention. Instead of simply asking, “Is she eating okay?” dig into what eating actually looks like.

How long does a meal take? Does the child eat the same foods as the rest of the family? Which foods do they accept or refuse? Do they seem hungry at mealtimes? What happens when a new food is introduced?

Ask about coughing, gagging, or choking. Does the child arch, cry, or seem uncomfortable during feeds? Do they sweat or tire while eating?

And don’t forget the question that can reveal an enormous amount: “Is mealtime stressful for you?”

The answers can point toward feeding difficulties, inadequate intake, swallowing problems, GI symptoms, cardiopulmonary concerns, or behavioral dynamics.

The guideline defines persistent faltering weight as faltering weight lasting more than 3 months despite initial treatment with higher-calorie foods, with therapy added when indicated. Persistence despite intervention is one of the signals that it may be time to broaden the workup.

When Should You Order Labs for Faltering Weight?

If the child has signs or symptoms suggesting a focal condition — or if the faltering weight is severe or persistent — targeted diagnostic testing may be appropriate.

But the guidelines don’t provide a go-to lab workup. Instead of thinking: Faltering weight = CBC, CMP, ESR, thyroid, celiac panel, stool studies…

Think targeted workup: What am I looking for, and what in this child’s history or examination makes me think it’s there?

When Should You Think About Endoscopy?

Not routinely.

Endoscopy should be reserved for children whose symptoms or clinical picture suggest a condition that requires it. If a child has persistent faltering weight, findings that might push you toward a GI evaluation include:

• Persistent vomiting

• Significant feeding problems

• Associated atopic disease

• Positive celiac screen

• Family history of conditions such as celiac disease or eosinophilic esophagitis.

When available, referral to pediatric gastroenterology is appropriate at this point.

How do you treat faltering weight?

Once you’ve identified inadequate intake, treatment gets wonderfully practical.

The AAP/NASPGHAN guideline recommends increasing calories and energy intake for children with faltering weight.

So start with what the child is actually eating.

A food diary can sometimes help clarify how much the child is taking in and where there may be opportunities to add calories. For infants and young children, this may involve increasing the energy density of foods rather than amount. The goal for breastfeeding infants is to add needed calories while minimizing unnecessary disruption to lactation. For children eating solids, families can add calorie-dense foods such as avocado, cream, butter, peanut butter, or oil.

Just as important is what not to do.

Excessive liquids, including juice, sweetened drinks, milk, and even water, can blunt appetite. Grazing throughout the day can make structured meals harder. Force-feeding can turn an already difficult mealtime into a battleground.

Instead, encourage predictable meals with the family when possible, model healthy eating behaviors, and continue offering foods multiple times and in different forms rather than immediately catering to a child’s narrow list of preferred foods.

When additional support is needed, a nutrition professional can help families incorporate supplemental protein or calories. For children who aren't able to meet their needs through food alone, the guideline supports the use of higher-energy formulas or oral nutritional supplements when appropriate.

When Is Feeding Therapy Appropriate?

Not every child who is a picky eater needs feeding therapy. But if feeding difficulties are contributing to a child's faltering weight, it's important to address the feeding problem itself, not just the number of calories going in.

The AAP/NASPGHAN guideline recommends feeding therapy for children with documented feeding difficulties. That might be a child who struggles with textures, has difficulty chewing or swallowing, eats a very limited variety of foods, or has meals that have become consistently stressful for the child and family.

In these cases, simply telling a family to “add more calories” may not get us very far. If a child can't tolerate the foods we're asking them to eat, or if every meal has become a battle, we need to address that piece of the puzzle, too.

The challenge, of course, is access. Feeding therapy can be difficult to find and even harder for families to fit into their schedules. But when feeding difficulty is part of why a child isn't taking in enough, it deserves to be part of the treatment plan.

Key Takeaways

Get good measurements. Ask good questions. Feed the kid. Follow closely.

And if that doesn’t work, then dig deeper.

That’s a framework clinicians can actually use and one that gives families a clearer, more compassionate path forward.

References:

1. Kersten HB, Goday PS, Abdelhadi R, et al; American Academy of Pediatrics; 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