Heart rate 38 on an adult - what does it mean?

Where 38 bpm sits on the adult scale

What a resting pulse of 38 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 38 bpm the heart beats about every 1.58 seconds — roughly 54,720 beats a day.

Asleep at 38 versus awake at 38

Many people first meet the number 38 on a sleep report from a watch or ring, not on a daytime check. That context changes everything. During sleep the heart rate typically falls 10 to 20 bpm below the waking resting value, and in fit people the drop can be larger. Someone who rests at 50 during the day may well touch the high 30s for a while at night.

The same 38 measured while you sit awake at a desk is a different matter. The band text above applies to that situation: a waking adult who is not a highly trained endurance athlete should get this checked promptly.

How the night-time curve normally looks

Heart rate is not flat through the night. It usually falls in the first hours, when deep non-REM sleep dominates and the vagus nerve slows the heart most, and it stays low for much of the night. During REM sleep, when dreams are vivid, the rate becomes more variable and may jump briefly. It climbs again toward waking, and rises further as you sit up and stand.

So a single low figure on the overnight graph says less than its shape. A smooth dip that recovers by morning is typical. Things that deserve a closer look include:

• sudden flat drops to a much lower value followed by quick jumps
• a saw-tooth pattern of repeated dips and rises through the night
• night-time lows paired with loud snoring, gasping or morning headaches
• a waking resting value that is also below 40

Making sense of wearable sleep data

Optical sensors are fairly accurate when you lie still, so a sleeping low of 38 is usually close to the truth. Brief gaps or wild spikes are more likely when the strap loosens or you lie on the arm. Look at the trend over several nights rather than one minimum value, and compare it with your morning resting value taken before getting up.

If you are fit, feel rested and your awake rate is in the 40s to 60s, a sleeping 38 fits the normal pattern. If you are not particularly active, if the low night values are new, or if you wake unrefreshed, take a week of graphs to your doctor. The resting heart rate page explains how to take the morning value.

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

• 33 bpm
• 34 bpm
• 35 bpm
• 36 bpm
• 37 bpm
• 39 bpm
• 40 bpm
• 41 bpm
• 42 bpm
• 43 bpm

Measured on a child instead? See heart rate 38 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.