Heart rate 45 on an adult - what does it mean?

Where 45 bpm sits on the adult scale

What a resting pulse of 45 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 45 bpm the heart beats about every 1.33 seconds — roughly 64,800 beats a day.

Reading 45 while on a beta blocker

People who take a beta blocker often notice their pulse settle lower than it used to be. A drop into the high 50s or low 60s is the usual, intended effect. A resting 45 goes further than most prescribers aim for, so it is worth a closer look, even if you feel fine.

The drug works by blocking the receptors that adrenaline and noradrenaline use to speed the heart. The higher the dose, the stronger that block. A few situations can push the rate lower than planned:

• a recent dose increase, or a switch to a longer-acting form
• a second rate-slowing medicine added on top, for example diltiazem, verapamil, digoxin or amiodarone
• weight loss, kidney or liver changes that alter how the drug is cleared
• good aerobic fitness on top of the medicine, since both effects add up
• taking an extra pill by mistake, which is easy with weekly pill boxes and two pharmacies

How to tell if 45 is too slow for you

The key question is whether your body copes with this rate. A beta blocker user who reads 45 at rest, walks briskly without trouble and feels clear-headed may simply be very well controlled. The same number with heavy legs, a foggy head, light-headedness when standing up or breathlessness on the stairs suggests the heart is not keeping up with demand.

Beta blockers also blunt the rise in pulse during effort. If a staircase that used to take you to 100 now only reaches the 70s and you feel drained, mention that too. It helps the doctor judge whether the dose fits your daily life, not only your resting minute.

Write down the time of each reading relative to your dose. Many tablets peak a few hours after they are taken, so a pre-dose reading and a peak reading can differ by several beats.

What to do next

Keep taking the medicine as prescribed and call the prescriber or a pharmacist within a few days to report the 45. Stopping a beta blocker abruptly can cause a sharp rebound in pulse and blood pressure, which is risky after a heart attack or with angina. Any change should come from the person who prescribed it, often as a smaller dose or a different timing.

Call 911 instead if 45 comes with fainting, chest pain, confusion or severe shortness of breath. The page on raising a slow heart rate explains the medical options doctors consider when a pulse is persistently too low.

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

• 40 bpm
• 41 bpm
• 42 bpm
• 43 bpm
• 44 bpm
• 46 bpm
• 47 bpm
• 48 bpm
• 49 bpm
• 50 bpm

Measured on a child instead? See heart rate 45 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.