GLP-1 Drugs and Nutritional Deficiencies in Children: Which Nutrients Are at Risk and What the Evidence Shows (2026)

A landmark 2026 study from Ann & Robert H. Lurie Children's Hospital of Chicago found that 16.8% of children aged 10–17 taking GLP-1 receptor agonists developed at least one nutritional deficiency within their first year of treatment — roughly one in six young patients. Vitamin D deficiency was the most frequently diagnosed problem, affecting 12.4% of the cohort, while nutritional anemia and iron-deficiency anemia rounded out the top three concerns. These findings, published in the peer-reviewed journal Childhood Obesity, arrive at a moment when GLP-1 prescriptions for pediatric obesity and diabetes are accelerating rapidly, making the nutritional safety profile of these drugs an urgent clinical question.

GLP-1 receptor agonists mimic the action of glucagon-like peptide-1, a gut hormone that stimulates insulin secretion, suppresses glucagon, slows gastric emptying, and reduces appetite. Originally developed for type 2 diabetes, they have since received regulatory approval for obesity management in both adults and, more recently, select pediatric populations. The appetite-suppressing and gastric-slowing mechanisms that make GLP-1 drugs therapeutically effective are precisely the mechanisms that raise nutritional red flags in growing children.

Key Findings at a Glance

Outcome Measured	Result (within 1 year)	Source
Any nutritional deficiency diagnosed	16.8% of 2,031 children	Kerr et al., Childhood Obesity, 2026
Vitamin D deficiency	12.4% of children	Kerr et al., Childhood Obesity, 2026
Nutritional anemia	1.55% of children	Kerr et al., Childhood Obesity, 2026
Iron-deficiency anemia	1.44% of children	Kerr et al., Childhood Obesity, 2026
Any deficiency within 180 days	10.2% of children	The Pharmaceutical Journal, 2026
Received nutritional counseling within 30 days	Only 5% of children	Northwestern University News, 2026
Received nutritional counseling within 180 days	Only 23.3% of children	Kerr et al., Childhood Obesity, 2026
Mean time to first nutrition counseling visit	149 days	Kerr et al., Childhood Obesity, 2026
Most prescribed GLP-1 in study cohort	Liraglutide (78.6%)	ScienceDaily, 2026

What Was the Study, and How Was It Conducted?

The research is a retrospective cohort analysis using national administrative claims data from the Inovalon database, spanning 2017 to 2022 and covering more than 100 million patients. From that dataset, researchers at Northwestern University and Lurie Children's Hospital identified 2,031 GLP-1 users aged 10 to 17 years who met continuous enrollment criteria and had no prior diagnosis of a nutritional deficiency before starting therapy.

The study cohort had a mean age of 15 years (±1.8 years), and 61.5% were female. Clinically, 62.6% had obesity, 67.2% carried a diagnosis of type 2 diabetes mellitus, 5.1% had prediabetes, and 27.7% had no recorded diabetes diagnosis at all — suggesting a meaningful proportion were receiving GLP-1 drugs primarily for weight management rather than glycemic control.

Nutritional deficiencies were identified using International Classification of Diseases, 10th edition (ICD-10) diagnostic codes for up to one year following GLP-1 initiation. Researchers also tracked nutrition therapy and counseling (NT/C) visits, time to first NT/C visit, and whether receiving counseling was associated with different deficiency rates. Group comparisons used chi-square tests.

The study's lead author was Kirk W. Kerr; the senior author was Justin Ryder, PhD, Vice Chair of Research for the Department of Surgery at Lurie Children's Hospital and Associate Professor of Surgery and Pediatrics at Northwestern University Feinberg School of Medicine. Funding was provided by Abbott.

One important methodological note: because this is a claims-based study, it captures diagnosed deficiencies — those detected and coded by a clinician. The true prevalence of nutritional inadequacy in this population is likely higher, since subclinical deficiencies that were never tested for or documented would not appear in administrative records.

Which Nutrients Are Most at Risk in Children Taking GLP-1 Drugs?

The three nutrients that researchers and clinicians consistently flag as highest-risk during GLP-1 therapy in pediatric patients are vitamin D, iron, and calcium. Each plays a distinct and irreplaceable role during adolescent development.

Vitamin D is a fat-soluble prohormone essential for calcium absorption, bone mineralization, immune function, and muscle development. In the study cohort, 12.4% of children were diagnosed with vitamin D deficiency within one year of starting GLP-1 therapy — making it by far the most common deficiency identified. This is not entirely surprising: vitamin D deficiency is already prevalent among adolescents with obesity even before pharmacologic treatment begins, since vitamin D is sequestered in adipose tissue and less bioavailable in individuals with higher body fat. GLP-1-driven appetite suppression and reduced dietary intake can compound this pre-existing vulnerability.

Iron is a trace mineral critical for hemoglobin synthesis, oxygen transport, cognitive development, and immune competence. The study found nutritional anemia in 1.55% and iron-deficiency anemia specifically in 1.44% of children within one year. While these percentages appear small in absolute terms, they represent clinically meaningful outcomes in a population screened out for pre-existing deficiencies at baseline. Iron deficiency during adolescence — particularly in females, who represented 61.5% of this cohort — can impair cognitive function, physical performance, and menstrual health.

Calcium is the primary mineral constituent of bone, with approximately 99% of the body's calcium stored in the skeleton. Adolescence is the single most critical window for bone accrual: roughly 40% of peak bone mass is accumulated during the teenage years. A calcium shortfall during this period cannot be fully compensated for later in life. While calcium deficiency was not separately broken out as a top-line finding in the study's ICD-10 coding results, senior author Justin Ryder explicitly named calcium alongside vitamin D and iron as nutrients of particular concern during adolescence.

Beyond these three, the broader literature on GLP-1-induced weight loss in adults points to potential inadequacies in zinc, folate, vitamin B12, and protein — all nutrients that support growth, neurological development, and immune function. The pediatric-specific data on these micronutrients remains thin, and the current study did not report them as primary findings, but they warrant monitoring in clinical practice.

Why Do GLP-1 Drugs Create Nutritional Risk in the First Place?

GLP-1 receptor agonists work through several overlapping mechanisms that, while therapeutically beneficial for weight and glycemic control, can reduce the quantity and quality of food children consume.

These drugs slow gastric emptying — food moves more slowly from the stomach into the small intestine, prolonging feelings of fullness and reducing meal size. They also act on appetite-regulating centers in the hypothalamus, directly suppressing hunger signals, while enhancing satiety hormones and blunting the reward response to food. The net effect is a substantial reduction in caloric intake, which drives the weight loss that makes these drugs effective.

The problem is that caloric restriction, especially when unplanned and unmonitored, does not selectively reduce empty calories. It reduces the intake of micronutrient-dense foods alongside everything else. A child eating significantly less food overall is at risk of eating significantly fewer vitamins and minerals — regardless of whether the food they do eat is nutritionally balanced.

This dynamic is well-documented in the adult GLP-1 literature. Evidence from adult populations suggests that pharmacologically induced weight loss and reduced intake may be accompanied by micronutrient inadequacies and loss of lean mass. The analogy to bariatric surgery is instructive: nutrient deficiencies are common in adolescents with severe obesity even before metabolic and bariatric surgery, and they frequently worsen after surgery despite supplementation. The researchers explicitly draw this parallel, suggesting a similar trajectory may apply to GLP-1 therapy.

For children and adolescents specifically, the stakes are higher than for adults. Adults have largely completed their skeletal development and pubertal maturation. Children have not. A nutritional shortfall during the growth window — particularly for bone-building minerals and hematopoietic nutrients — can have consequences that persist into adulthood.

Which GLP-1 Drugs Are Children Actually Being Prescribed?

In the study cohort drawn from 2017 to 2022, liraglutide (sold under the brand names Victoza and Saxenda) was by far the most commonly prescribed GLP-1 medication, accounting for 78.6% of prescriptions. Dulaglutide (Trulicity) accounted for 10.4%, and semaglutide (Ozempic and Wegovy) accounted for 9.1%.

This distribution reflects the regulatory space of the study period. Liraglutide received FDA approval for pediatric obesity (ages 12 and older) in 2020, making it the dominant agent in the early years of pediatric GLP-1 use. Semaglutide's pediatric obesity approval came later, in 2023, which is why it represents a smaller share in a dataset ending in 2022. The current prescribing landscape in 2026 likely looks quite different, with semaglutide now accounting for a much larger share of new pediatric starts.

The UK regulatory picture is notably more restrictive. Sukhi Basra, vice chair of the National Pharmacy Association, noted that in the UK only liraglutide (Saxenda; Novo Nordisk) is licensed for adolescents aged 12 to 17 with a BMI of 30 or above and a body weight of over 60kg, and only as part of a specialist paediatric weight management service. Semaglutide and tirzepatide remain adult-only medicines in the UK. This means the nutritional risk profile identified in the US study may be less acute in countries with tighter prescribing guardrails — but the underlying pharmacological mechanism is the same wherever these drugs are used.

Off-label prescribing is also a meaningful factor. Research has shown off-label prescribing of semaglutide to be sizable, with 2023 estimates ranging from 22.1% to 30% of semaglutide prescriptions, and that patients receiving off-label prescriptions are younger and more likely to have an obesity diagnosis. Off-label use, by definition, occurs outside the structured monitoring frameworks that accompany approved indications — which may mean these patients are at even greater risk of falling through nutritional safety nets.

How Big Is the Gap in Nutritional Counseling?

The counseling data in this study is its most actionable finding. Only 5% of patients received nutritional counseling within 30 days of starting GLP-1 treatment, and fewer than 25% received it within six months. The mean time to a first nutrition therapy or counseling visit was 149 days — nearly five months after treatment initiation.

This gap is striking given that the study also found patients who did receive nutrition therapy/counseling had higher rates of nutritional deficiencies and deficiency-related complications than those without (23.2% vs. 14.8%, p < 0.01). This counterintuitive finding almost certainly reflects selection bias rather than a harmful effect of counseling: children referred to a dietitian were probably those already showing signs of nutritional concern, or those whose clinicians had flagged them as higher risk. The counseling was reactive rather than preventive.

That reactive pattern is precisely what the study authors argue must change. "Nutritional support needs to play a critical role once treatment with a GLP-1 medication is initiated," said Dr. Ryder, "as opposed to waiting until a nutritional deficiency is diagnosed." The current data suggests the system is doing the opposite.

The contrast with specialist pediatric care in the UK is instructive. Basra noted that within specialist paediatric services, dietetic and nutritional input is not an add-on — it is part of the fabric of care from day one, because clinicians are not just treating a number on a scale, they are safeguarding a child's growth and development. The US data suggests that this integrated model is not yet the norm in American prescribing practice, particularly in non-specialist settings.

What Are the Long-Term Implications of These Deficiencies?

The developmental stakes of nutritional deficiency during adolescence are well established in the broader medical literature, even if the GLP-1-specific long-term data in children is still nascent.

Vitamin D deficiency during the teenage years is associated with reduced bone mineral density, increased fracture risk, impaired muscle function, and — in severe cases — rickets or osteomalacia. Because peak bone mass is largely determined by age 25, deficiencies that occur during the adolescent growth spurt can permanently reduce skeletal reserve, increasing the risk of osteoporosis decades later.

Iron deficiency, even without frank anemia, impairs cognitive function, attention, and academic performance. In adolescent females, it can disrupt menstrual cycles and, in severe cases, affect reproductive health. The 1.44% rate of iron-deficiency anemia in this cohort — again, in children who had no deficiency at baseline — represents a real clinical burden.

Calcium shortfalls compound the vitamin D problem: without adequate calcium, even sufficient vitamin D cannot fully support bone mineralization. The two nutrients work in tandem, and a deficit in either undermines the other's effectiveness.

For children being treated for obesity or diabetes, the irony is sharp. GLP-1 drugs are prescribed to improve long-term cardiometabolic health, but if nutritional monitoring is inadequate, they may simultaneously create new long-term risks in skeletal and hematological health. This does not mean the drugs should not be used — their benefits for metabolic disease are substantial and well-documented — but prescribing them without nutritional infrastructure is incomplete care.

What Should Clinicians and Families Do?

The study's authors are explicit that their findings are not a call to restrict GLP-1 use in children, but rather a call to restructure how that use is supported. Several practical implications emerge from the data.

Baseline nutritional screening before initiation. Given that adolescents with obesity already have elevated rates of vitamin D and iron deficiency before any pharmacologic treatment, a baseline panel of micronutrient levels — at minimum vitamin D, iron studies, and a complete blood count — should be standard before starting GLP-1 therapy. This establishes a reference point and identifies children who are already at the lower end of normal.

Proactive, not reactive, nutritional counseling. The 5% rate of counseling within 30 days is a system failure, not a patient failure. Integrating a dietitian referral into the GLP-1 initiation workflow — rather than waiting for a deficiency diagnosis — is the structural change the authors advocate. The mean 149-day lag to first counseling visit means that, for most children, a deficiency has already had months to develop before any nutritional support is provided.

Ongoing monitoring during treatment. Nutritional status is not static. A child who starts GLP-1 therapy with adequate vitamin D levels may become deficient as appetite suppression reduces dietary intake over months. Periodic re-testing — particularly at the 3-month and 6-month marks — allows early detection and correction before deficiencies become clinically significant.

Supplementation as a bridge. For children at high risk — particularly those with severe obesity, those on very low-calorie intakes, or those in rapid pubertal growth phases — prophylactic supplementation with vitamin D and iron (where appropriate) may be warranted while dietary counseling is being established. This is consistent with practice in bariatric surgery programs, which routinely provide post-operative micronutrient supplementation.

Family and patient education. Children and their caregivers need to understand that GLP-1 medications reduce appetite by design, and that eating less does not automatically mean eating worse — but it requires deliberate attention to food quality. Practical guidance on nutrient-dense eating patterns, even at reduced caloric volumes, is a core component of safe GLP-1 management in pediatric patients.

For families navigating these questions, nutritional support tools — including algae-based omega-3 supplements and evidence-based micronutrient strategies — may be worth discussing with a pediatric dietitian as part of a full care plan.

What Are the Limitations of This Evidence?

The study is important and timely, but it has real limitations that should inform how the findings are interpreted.

As a claims-based analysis, it captures only diagnosed deficiencies — those that were tested for, identified, and coded by a clinician. Children who were not tested, or whose deficiencies were subclinical, would not appear in the data. This means 16.8% is almost certainly an undercount of the true prevalence of nutritional inadequacy in this population.

The study also cannot establish causation. Children taking GLP-1 drugs for obesity and diabetes are a clinically complex population with multiple risk factors for nutritional deficiency independent of the medication — including dietary patterns associated with obesity, socioeconomic factors affecting food access, and the metabolic effects of diabetes itself. The study design does not include a matched control group of children with obesity or diabetes who did not receive GLP-1 therapy, which would be needed to isolate the drug's specific contribution to deficiency risk.

The dataset spans 2017 to 2022, a period when liraglutide dominated pediatric GLP-1 use. The nutritional risk profile of newer, higher-potency agents like semaglutide and tirzepatide — which produce greater appetite suppression and larger reductions in food intake — may differ from what this study captured. The 2026 prescribing space, in which semaglutide is far more prevalent, may carry different and potentially greater nutritional risks than the historical data suggests.

Finally, the study was funded by Abbott, a manufacturer of nutritional products. This does not invalidate the findings — the methodology is sound, and the results were published in a peer-reviewed journal — but it is a relevant disclosure for readers evaluating the evidence.

The Bottom Line

GLP-1 receptor agonists carry meaningful nutritional risk in pediatric patients — not as a reason to avoid them, but as a reason to prescribe them more carefully. The evidence from this 2026 study is clear: nearly one in six children developed a nutritional deficiency within their first year of GLP-1 therapy, and the current standard of care is failing to provide timely nutritional support. Only 5% of patients received counseling within 30 days, and fewer than one in four received it within six months.

Adolescence is the developmental window during which the body builds the skeletal, hematological, and metabolic foundations it will rely on for decades. Vitamin D, iron, and calcium are not optional nutrients during this period — they are structural requirements. A medication that reduces appetite without a corresponding system to protect nutritional adequacy is an incomplete treatment.

The fix is not complicated in concept, even if it requires system-level change in practice: screen before prescribing, counsel at initiation, monitor throughout treatment, and supplement where needed. These are the standards already embedded in specialist pediatric weight management services in countries like the UK. They should become the standard everywhere GLP-1 drugs are prescribed to children.