Rapid heart rate in infants and toddlers.
A fast heart rate in a young child isn’t always serious — but it’s one of the most important vital signs to track. It can be an early indicator of fever, dehydration, respiratory distress, or something that needs prompt attention.
Why heart rate matters in young children
In infants and toddlers, the heart rate is one of the most sensitive indicators that something is wrong. Unlike older children and adults, young children cannot reliably tell you they feel unwell — their vital signs speak for them.
A rapid heart rate (tachycardia) occurs when the heart beats faster than normal for the child’s age. Because the ranges vary so much by age, what looks fast in a 5-year-old may be completely normal in a 2-month-old.
Heart rate rises in response to fever, pain, dehydration, and breathing difficulty. When a child’s heart is working harder than usual, it’s worth taking seriously — and documenting accurately so your provider has the full picture.
What’s normal — and what’s rapid?
Heart rate norms change significantly as children grow. Always measure when your child is calm and resting — crying, activity, and fever all raise the rate.
| Age | Normal Resting Rate | Rapid (Tachycardia) |
|---|---|---|
| Newborn (0–1 month) | 70–190 bpm | Above 190 bpm |
| Infant (1–11 months) | 80–160 bpm | Above 160 bpm |
| Toddler (1–2 years) | 80–130 bpm | Above 150 bpm |
| Preschool (3–4 years) | 80–120 bpm | Above 140 bpm |
| School age (5–6 years) | 75–115 bpm | Above 130 bpm |
What causes a rapid heart rate in young children?
Most causes are treatable — but some require prompt attention.
Fever
The most common cause. Heart rate rises approximately 10 bpm for every 1°F above normal. Once fever is treated, heart rate typically returns to normal within 30–60 minutes.
Dehydration
When fluid volume drops, the heart compensates by beating faster. Watch for dry mouth, fewer wet diapers, and dark urine alongside a fast heart rate.
Respiratory distress
When breathing is labored, the heart works harder to deliver oxygen. A rapid heart rate alongside noisy or fast breathing warrants prompt evaluation.
Pain or distress
Crying, pain, and anxiety all raise heart rate temporarily. Always measure when your child is calm — ideally when they’re asleep or settled.
Anemia
Low red blood cell counts mean the heart must beat faster to circulate enough oxygen. Often accompanied by pallor, fatigue, and poor feeding in infants.
Cardiac arrhythmia
Rare, but a persistently elevated heart rate without fever or distress — especially above 220 bpm — may indicate a rhythm problem requiring immediate evaluation.
Signs that need prompt attention
Contact your provider — or go to the emergency department — if your child’s rapid heart rate is accompanied by any of the following:
- Heart rate persistently above the upper limit for their age, at rest, without fever or distress
- Difficulty breathing, chest retractions, or noisy breathing alongside a fast heart rate
- Pale, grey, or bluish skin — especially around the lips or fingernails
- Unusual drowsiness, limpness, or difficulty waking
- Poor feeding, vomiting, or signs of significant dehydration
- Heart rate above 220 bpm at any age, at rest
- A rapid heart rate that doesn’t slow down after fever is treated and your child is calm
Check your child’s heart rate now
Enter your child’s age, start the 20-second timer, count each heartbeat, then enter the number — the calculator tells you if it’s within the normal range for their age.
1. Child’s age
2. Measure the pulse
How to measure your child’s heart rate
This short video walks you through checking your child’s heart rate at home accurately — and what to watch for.
See it. Treat it. Track it.
Log your child’s heart rate in MamaBear and share it directly with your provider — no appointment needed.