Heart rate 48 on an adult - what does it mean?

Where 48 bpm sits on the adult scale

What a resting pulse of 48 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 48 bpm the heart beats about every 1.25 seconds — roughly 69,120 beats a day.

Potassium and a heart that slows to 48

Every heartbeat depends on charged particles moving in and out of heart cells. Potassium, sodium, calcium and magnesium set the electrical charge that lets the pacemaker cells fire and the signal travel to the ventricles. When one of these minerals drifts far from its normal level, the rhythm can change. A resting pulse of 48 in someone who is not an endurance athlete is one situation where a doctor will usually check them.

Too much potassium in the blood, called hyperkalemia, is the classic electrolyte cause of a slow heart. High levels make heart cells less excitable and can slow conduction, leading to a slower rate or heart block. Very high potassium is dangerous because it can trigger serious rhythm problems with little warning.

Who is more likely to have a high potassium level

Healthy kidneys remove extra potassium efficiently, so a high level usually has a reason behind it. Common ones include:

• chronic kidney disease or a sudden drop in kidney function, for instance during dehydration or severe illness
• blood pressure and heart medicines that hold on to potassium, such as ACE inhibitors, ARBs, spironolactone and other potassium-sparing diuretics
• potassium supplements or salt substitutes made with potassium chloride, especially combined with the drugs above
• uncontrolled diabetes and some hormone problems of the adrenal glands

Several of these often appear together. An older adult with kidney disease who takes an ACE inhibitor and a beta blocker, then uses a potassium salt substitute, has more than one push toward a slow pulse.

Low potassium and low magnesium matter too, but they more often cause extra beats and fast irregular rhythms than a steady slow one. Low calcium is rarely a cause of a slow rate on its own.

What to do with a reading of 48

If you have kidney disease or take any of the medicines listed and see a new resting rate in the 40s, contact your doctor soon and ask whether a blood test for electrolytes and kidney function is due. Do not stop prescribed drugs or start cutting potassium-rich foods on your own; changes should be based on a measured level.

Muscle weakness, nausea, a fluttering or irregular beat, or feeling faint together with a slow pulse can signal a dangerous potassium level and needs emergency care. A basic metabolic panel and an ECG answer the question quickly. More on what drives a slow resting value is on the resting 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

• 43 bpm
• 44 bpm
• 45 bpm
• 46 bpm
• 47 bpm
• 49 bpm
• 50 bpm
• 51 bpm
• 52 bpm
• 53 bpm

Measured on a child instead? See heart rate 48 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.