Heart rate 40 on an adult - what does it mean?

Where 40 bpm sits on the adult scale

What a resting pulse of 40 means

Endurance training makes the heart muscle stronger, so it moves more blood per beat and needs fewer beats at rest. Runners, cyclists and swimmers commonly rest between 40 and 60 bpm. During sleep, almost everyone's heart rate drops 10–20 bpm below the daytime resting value.

If you are not particularly fit, possible causes include medications (beta blockers and other heart-rate-lowering drugs), an underactive thyroid (hypothyroidism), sleep apnea and conduction problems of the heart. These are easy to check with an ECG and a blood test, or a sleep study for sleep apnea.

Ranges apply to adults and children aged 10 and older, measured at rest (American Heart Association). By the numbers: at 40 bpm the heart beats about every 1.50 seconds — roughly 57,600 beats a day.

Forty bpm: same number, two very different people

A resting rate of 40 is where the low band begins on this scale, and it is a number that means opposite things for different readers. For a runner, cyclist, rower or triathlete training most days, 40 at rest is often a sign of an efficient heart. Athletes’ resting rates commonly fall between 40 and 60. For someone who rarely exercises, the same 40 has no obvious explanation and deserves a look for causes.

So the useful question is not whether 40 is good or bad, but which group you honestly belong to. Jogging twice a week is healthy, but it rarely produces this degree of slowing on its own.

A quick self-check: does the athletic explanation fit?

• Training load. Do you do several hours of sustained aerobic exercise each week, and have you done so for months or years?
• Trend. Did your resting rate fall gradually as your fitness rose, or did it drop suddenly without any change in training?
• Effort response. Does your pulse climb quickly and high when you push hard, and come back down promptly afterwards?
• How you feel. Are you free of dizzy spells, blackouts, unusual breathlessness and unexplained loss of performance?

Yes to all four makes an athletic slow heart likely. A no to any of them, especially the last, is a reason to see a doctor even if you are fit.

What a check-up at 40 usually involves

For a non-athlete with a confirmed resting 40, the first steps are simple. The doctor reviews medicines, since beta blockers, some calcium channel blockers and digoxin commonly lower the rate. An ECG shows whether the beat starts normally and passes through the heart without blocks. Blood tests check thyroid function and electrolytes. Questions about snoring and daytime sleepiness screen for sleep apnea.

Athletes are sometimes offered an exercise test to confirm that the rate rises properly. A drop in training for a few weeks, with resting rates creeping back up, also supports the athletic explanation.

Keep in mind that even fit people take medicines, have thyroid problems and age. A slow pulse that was once explained by training can later have another cause. If your rate stays at 40 while you are less active, for example during an injury break, mention it. To compare your number with the general population, see the normal adult heart rate overview.

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

• 35 bpm
• 36 bpm
• 37 bpm
• 38 bpm
• 39 bpm
• 41 bpm
• 42 bpm
• 43 bpm
• 44 bpm
• 45 bpm

Measured on a child instead? See heart rate 40 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.