Heart rate 143 on an adult - what does it mean?

Where 143 bpm sits on the adult scale

What a resting pulse of 143 means

If you just climbed stairs, exercised or are very anxious, a pulse of 143 can be a normal response and should fall within minutes. A fast rate that persists at rest can come from fever, dehydration, blood loss or anemia, an overactive thyroid, or a heart rhythm disorder such as atrial fibrillation, atrial flutter or supraventricular tachycardia (SVT).

An irregular pulse at this speed is a typical sign of atrial fibrillation, which raises stroke risk and should always be evaluated.

Ranges apply to adults and children aged 10 and older, measured at rest (American Heart Association). By the numbers: at 143 bpm the heart beats about every 0.42 seconds — roughly 205,920 beats a day.

Why 143 is routine for a baby and a warning sign for you

A heart rate only means something next to the right scale. In the first months of life, a resting pulse in the 140s is entirely ordinary. Over childhood the resting rate falls steadily, and from about age 10 the adult range of 60 to 100 applies. So a parent who counts 143 on a calm infant and a grown-up who sees 143 on their own watch are looking at the same number with opposite meanings.

The reason is mostly size. A small heart pushes out only a small amount of blood with each beat. A baby’s body also burns energy quickly for its weight and loses heat fast. To deliver enough blood and oxygen, the little heart has to beat often. As the heart grows, each beat moves more blood, and the rate can drop.

Adults have less room to speed up

A grown-up heart at rest is designed to cruise. An adult reaching 143 without moving means the heart is answering some strong demand: fever, fluid loss, low blood counts, a hormone problem, a stimulant, or a rhythm that is not starting in the normal place. That is why this page rates 143 as high for adults and why the same number can sit in the expected range for a young child.

Teenagers are in between. The adult scale is used for them, but they are often a little faster at rest than their parents, and they speed up more on standing. A teen at 143 at rest still needs the same attention as an adult.

If you measured someone else

• A baby or toddler: switch this page to the child view (the link is under the nearby values) to see the infant and young-child ranges. Count when the child is calm or asleep, since crying and feeding raise the rate a lot.
• A child under 10: the child ranges apply, and they narrow with each year of age.
• A teenager or adult: the adult scale and the advice at the top of this page apply.

In children, how they look matters as much as the number. Call 911 or go to the emergency department for a child who is floppy, very pale or bluish, breathing fast or with effort, or unusually hard to wake. A child who refuses to drink needs a doctor the same day.

For an adult at rest, the rule stays simple: rest, re-measure, and if the rate is still above 120 after ten to fifteen minutes, contact a doctor today. To compare ages, see the human heart rate.

For a reliable resting value, sit quietly for five minutes first and average a few mornings: Resting Heart Rate: What It Says About Your Health. You can also measure by tapping along on the start page.

Nearby values

• 138 bpm
• 139 bpm
• 140 bpm
• 141 bpm
• 142 bpm
• 144 bpm
• 145 bpm
• 146 bpm
• 147 bpm
• 148 bpm

Measured on a child instead? See heart rate 143 in a child.

Sources: American Heart Association: All About Heart Rate · MedlinePlus: Pulse · ACSM position stand on exercise intensity (2011)

This page explains a single reading in general terms. It is not a diagnosis. Heart rate alone cannot tell whether the rhythm is regular or whether the heart is healthy — if you are worried, talk to a doctor.