Seeing "38" flash on your smartwatch in the middle of the night can be terrifying. It’s a low number. Most people sit somewhere between 60 and 100 beats per minute, so when yours drops into the thirties, it feels like your heart is barely trying.
But here is the thing: context matters more than the number itself.
Technically, a 38 bpm heart rate is a condition called bradycardia. In medical speak, anything under 60 is bradycardia. But if you’re a marathon runner or someone who spends five days a week on a Peloton, that 38 might just be a badge of an incredibly efficient cardiovascular system. If you’re feeling dizzy, short of breath, or like you’re about to pass out, that’s a completely different conversation. We need to look at the "why" behind the pulse.
What is actually happening inside your chest at 38 bpm?
Your heart is a pump. It’s a muscular bag that squeezes blood to your brain, toes, and everywhere in between. When your heart rate is 38 bpm, it means that pump is only firing about once every 1.5 seconds.
For a normal person, that’s not enough. The brain gets hungry for oxygen. You start feeling "gray," which is that weird, fuzzy feeling right before a faint. However, elite athletes often have hearts that have grown larger and stronger—the Left Ventricular Hypertrophy (the "athlete's heart"). Because the pump is so powerful, it can move a massive amount of blood in a single squeeze. It doesn’t need to beat 70 times a minute. It can do the same job in 38.
Take Miguel Induráin, the five-time Tour de France winner. His resting heart rate was famously reported at 28 bpm. At 38, he would have been practically "revving" his engine.
But you probably aren't a Tour de France winner.
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If you aren't training for a triathlon, a 38 bpm heart rate often points toward an electrical issue. The heart has its own internal wiring system, starting at the Sinoatrial (SA) node. If that node gets sleepy—sick sinus syndrome—or if the signal gets blocked on its way to the bottom chambers (heart block), the rate plummets. This isn't efficiency; it's a hardware failure.
When 38 bpm is a genuine emergency
Honestly, the symptoms tell the story better than the pulse ox. If you have a 38 bpm heart rate and you feel fine, you likely have high vagal tone. The vagus nerve is like the brake pedal for your heart. Some people just have a heavy foot on that brake, especially during deep sleep.
However, you need to head to the ER if that 38 is accompanied by:
- Chest pain (angina).
- Cold, clammy skin.
- Confusion or "brain fog."
- Syncope (actually passing out).
- Extreme fatigue doing basic tasks like walking to the mailbox.
Basically, if your heart isn't beating fast enough to keep your blood pressure up, your organs start to struggle. This is "symptomatic bradycardia," and it's usually treated with a pacemaker.
The role of medications and outside factors
Sometimes the heart is fine, but it's being suppressed. Beta-blockers are a huge culprit here. Drugs like Metoprolol or Atenolol are designed to slow the heart down to lower blood pressure or protect the heart after a heart attack. If the dose is a bit too high, or if you've recently lost weight, that dose might suddenly be too much, dragging you down into the 30s.
Calcium channel blockers like Verapamil or Diltiazem do similar things.
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Then there’s the chemistry of your blood. Electrolytes are the "juice" that makes the electrical signals happen. If your potassium is too high (hyperkalemia) or your thyroid is sluggish (hypothyroidism), your heart rate will tank. I’ve seen patients come in with a 38 bpm heart rate thinking they need a pacemaker, only to find out their thyroid was barely functioning. Once the hormones were fixed, the heart rate bounced right back to 65.
Why sleep changes everything
It’s totally normal for your heart rate to crater while you sleep. When you enter REM or deep sleep stages, your body’s demand for oxygen drops significantly. For many people, a 38 bpm heart rate during sleep is unremarkable.
The concern is when that low rate is paired with Sleep Apnea. If you stop breathing, your oxygen levels drop, and your heart rate can fluctuate wildly—slowing down significantly before spiking as you gasp for air. If your Apple Watch or Garmin shows you're hitting 38 bpm frequently at night, it might be worth checking if you’re also snoring like a chainsaw or waking up with a headache.
Diagnostics: Getting to the bottom of the 30s
If you go to a cardiologist with this concern, they aren't just going to take your pulse and send you home. They'll start with an EKG (or ECG). This gives a 10-second snapshot of the heart's electrical rhythm. They're looking for things like "P-waves"—the little bumps that signify the top of the heart is telling the bottom to beat.
If the EKG is clean but the low rate persists, you’ll likely wear a Holter monitor.
It's a little device with stickers on your chest that records every single heartbeat for 24 to 48 hours. This is crucial because it catches the 38 bpm heart rate in action. Does it happen when you're stressed? When you're sleeping? When you're standing up? The "when" is just as important as the "what."
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In some cases, they might do a Stress Test. They put you on a treadmill and turn up the speed. If your heart rate stays at 38 or only crawls up to 50 while you're sprinting, that's "chronotropic incompetence." It means your heart can't find the gas pedal. That is a clear sign that the heart's natural pacemaker is failing.
Can you live a normal life with a heart rate this low?
Absolutely. If you’re an athlete, 38 bpm is often a sign of health.
But let’s be real: for the average person, it’s a yellow light. It’s the body saying, "Hey, keep an eye on this." You might find you're more sensitive to cold, or you get tired a little earlier in the evening than your friends.
The treatment, if needed, is surprisingly routine. Modern pacemakers are about the size of a silver dollar and can be implanted in a quick procedure. They don't take over the heart; they just "watch." If the heart rate stays above the set limit (usually 60), the pacemaker does nothing. If the heart tries to drop to 38, the pacemaker gently steps in and provides the beat.
Actionable steps for managing a low heart rate
If you've noticed your heart rate is consistently hitting 38 bpm, don't panic, but don't ignore it either. Start with these concrete steps to figure out where you stand.
- Log your symptoms immediately. Keep a note on your phone. When you see that 38 on your watch, write down exactly how you feel. Are you dizzy? Perfectly fine? Just finished a workout? This data is gold for a doctor.
- Check your supplements. Things like magnesium or certain herbal teas can occasionally influence heart rhythm. Bring the bottles to your appointment.
- Hydrate and check electrolytes. Dehydration or an imbalance in salts can mess with the electrical conduction of your heart. Ensure you're getting enough potassium and sodium, especially if you exercise heavily.
- Review your meds. Look at the side effects of everything you take, including over-the-counter stuff. If "bradycardia" or "slowed heart rate" is on the list, you have your prime suspect.
- Book a baseline EKG. Even if you feel great, having a record of your "normal" 38 bpm is vital. If something changes in the future, doctors need to know that 38 was your starting point.
A 38 bpm heart rate is rarely a "nothing" find, but it's also not an automatic death sentence. It’s a signal from your most vital organ. Listen to it, verify it with a professional, and adjust your lifestyle or treatment accordingly.