Heart rate 39 on an adult - what does it mean?

Where 39 bpm sits on the adult scale

What a resting pulse of 39 means

Very slow resting rates in people who are not highly trained can mean the heart's electrical system is not keeping pace — for example sinus node dysfunction or a heart block — or can be a medication effect (beta blockers, some calcium channel blockers, digoxin). An underactive thyroid, low body temperature and electrolyte problems are other causes.

Rule out a measuring error first: a weak or irregular pulse is easy to undercount by hand, and some wrist wearables miss beats. Count for a full 60 seconds at the wrist or use a chest-strap or blood-pressure monitor.

Ranges apply to adults and children aged 10 and older, measured at rest (American Heart Association). By the numbers: at 39 bpm the heart beats about every 1.54 seconds — roughly 56,160 beats a day.

The top of the very low band

On this site’s scale, 39 is the last whole number in the very low group. One beat more and the reading moves into the low band that starts at 40. That border is a convenience for sorting readings, not a biological switch. A doctor will not treat 39 very differently from 41. What tells the two apart in practice is the rhythm behind the number, and that is what an ECG is for.

Doctors also weigh who is attached to the number. A 25-year-old rower, a 70-year-old on a beta blocker and a tired middle-aged office worker can all read 39 for completely different reasons.

What the ECG tracing actually shows

A resting 12-lead ECG takes a few minutes and is painless. Sticky electrodes on the chest, arms and legs pick up the tiny electrical signals of each heartbeat. For a slow rate, the doctor reads a handful of features:

• P waves: small bumps that show the upper chambers firing. Their presence and shape reveal whether the beat starts in the sinus node.
• PR interval: the delay between upper and lower chambers. A long but fixed delay is first-degree block, often harmless; a delay that grows until a beat drops, or beats that drop suddenly, is second-degree block.
• The link between P waves and QRS complexes: if every P is followed by a QRS, the conduction path works. If they march independently, the upper and lower chambers are disconnected.
• QRS width: narrow complexes suggest the beat starts high up; wide ones suggest a backup rhythm lower in the heart.

The report may simply say sinus bradycardia, meaning the natural pacemaker is in charge and just slow. That is the most common finding in fit people and in people on rate-lowering medicine.

When one tracing is not enough

A resting ECG captures only about ten seconds of rhythm. If symptoms come and go, a portable recorder worn for a day or longer may follow. Blood tests for thyroid function, potassium and kidney function are usually done at the same visit.

Bring a log of home readings with times, and note how you felt. Until you are seen, which should be soon at this rate, avoid driving if you feel light-headed, and call 911 for fainting, chest pain or severe breathlessness. More on heart rhythm basics is on the human heart rate page.

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

• 34 bpm
• 35 bpm
• 36 bpm
• 37 bpm
• 38 bpm
• 40 bpm
• 41 bpm
• 42 bpm
• 43 bpm
• 44 bpm

Measured on a child instead? See heart rate 39 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.