Growth Spurts and Blood Health: What Parents Should Know About Iron, Energy, and Development

Your child suddenly needs new shoes.

Their pants seem too short overnight. They're eating everything in sight, sleeping longer, and somehow still seem tired.

Welcome to a growth spurt.

Most parents expect growth spurts to bring bigger appetites and extra sleep. But sometimes, they also notice something else:

Lower energy.
Less endurance.
More naps.
A child who suddenly seems exhausted.

It's easy to assume this is simply part of growing up.

And sometimes, it is.

But rapid growth places significant demands on the body—including the systems responsible for making blood, transporting oxygen, and supporting energy production.

Understanding how growth spurts affect blood health can help parents better support their child's development and recognize when certain changes may deserve closer attention.

 

What Happens During a Growth Spurt?

Growth spurts are periods of accelerated physical development.

During these phases, children and adolescents experience rapid changes in:

• Height
• Muscle mass
• Bone development
• Hormonal activity
• Brain maturation
• Blood volume

These periods of rapid growth require substantial amounts of energy and nutrients.

In fact, adolescence represents one of the fastest periods of growth outside of infancy [1].

The body isn't simply getting taller—it is building and reorganizing multiple systems simultaneously.

 

Why Growth Increases the Demand for Iron

As children grow, their bodies need to produce more blood.

Blood volume naturally expands to support a larger body, and additional red blood cells are needed to transport oxygen efficiently throughout growing tissues.

This process increases demand for nutrients involved in red blood cell production, particularly:

• Iron
• Protein
• Vitamin B12
• Folate

Iron is especially important because it helps produce hemoglobin, the protein in red blood cells that carries oxygen throughout the body [2].

As growth accelerates, iron requirements increase as well.

 

Why Growing Kids Sometimes Feel Tired

Many parents notice that children seem unusually tired during growth spurts.

Several factors can contribute:

The body is using significant amounts of energy for growth.

Sleep requirements often increase.

Nutrient demands rise rapidly.

At the same time, expanding blood volume and increased red blood cell production place additional demands on iron stores.

If nutritional intake doesn't keep pace with growth, children may experience symptoms such as:

• Fatigue
• Lower exercise tolerance
• Difficulty concentrating
• Reduced endurance
• Feeling sluggish

Because these symptoms often develop gradually, they're easy to attribute entirely to growing up.

 

 

Why Teenagers Are at Higher Risk

Adolescence is a particularly important period for blood health.

Rapid growth, changing hormone levels, and increased activity all increase nutritional needs.

According to the National Institutes of Health, adolescents are among the groups at increased risk for iron deficiency because of these heightened physiological demands [2].

Certain groups may face additional challenges:

Teenage Girls

The combination of rapid growth and menstrual blood loss can further increase iron needs.

Young Athletes

Intense physical activity increases oxygen demands and places additional stress on recovery systems.

Picky Eaters

Restrictive eating patterns may make it more difficult to meet increased nutrient requirements.

 

The Signs Parents Often Miss

Growth spurts don't always look the way parents expect.

Sometimes the signs are obvious:

Suddenly outgrown clothes.
Increased appetite.
Sleeping later.

Other times, the signs are more subtle.

A child who:

• Gets tired more easily
• Seems less motivated during sports
• Has difficulty focusing
• Needs more rest than usual
• Complains of feeling low energy

None of these symptoms automatically indicate a health problem.

But they can serve as reminders that rapid development increases demands on the body.

 

Why Blood Health Matters During Development

Blood plays a central role in supporting growth.

It delivers:

• Oxygen to developing tissues
• Nutrients to muscles and organs
• Hormones throughout the body
• Energy-producing resources for cells

When nutrient demands increase during growth spurts, blood health becomes even more important.

Supporting healthy development isn't only about tracking height and weight. It's also about understanding the physiological changes happening behind the scenes.

 

Why Monitoring Patterns Matter

Growth doesn't happen on a predictable schedule.

Children may experience periods of rapid change followed by slower phases of development.

That's why paying attention to patterns can be helpful.

Parents may notice:

• Changes in appetite
• Shifts in energy levels
• Differences in athletic performance
• Increased sleep needs
• Fluctuations in recovery

Observing these trends over time often provides more meaningful insight than focusing on any single day or symptom.

 

Looking Beyond the Growth Chart

Growth charts tell an important story—but they're only one part of development.

Blood health helps support the processes happening behind every growth spurt.

The Ruby app offers a simple way to monitor blood health trends over time. Using fingernail selfie technology, Ruby estimates an Iron Score, which reflects the likelihood of iron-related changes, and a Circulation Score, which reflects how blood is moving through the fingertips.  

These wellness insights aren't diagnostic, but they can help families better understand patterns that may influence energy, recovery, and overall wellness during periods of rapid growth.

Download Ruby on  iOS  or  Android  to start tracking today.

As always, if your child experiences persistent fatigue, weakness, dizziness, or concerning symptoms, consult a qualified healthcare provider.

 

References

[1] Centers for Disease Control and Prevention. "Child and Teen BMI Categories and Growth Charts."
https://www.cdc.gov/bmi/child-teen-calculator/bmi-categories.html

[2] National Institutes of Health Office of Dietary Supplements. "Iron Fact Sheet for Health Professionals."
https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/

[3] American Academy of Pediatrics. "Ages and Stages: Adolescent Development."
https://www.healthychildren.org/English/ages-stages/teen/Pages/default.aspx

[4] Nemours KidsHealth. "Growth and Your 13- to 18-Year-Old."
https://kidshealth.org/en/parents/growth-13-to-18.html