Why does my heart race at 3 a.m. every night – thyroid, anxiety, or something else?

By Sina Hartung, MMSC-BMI, Harvard Medical SchoolReviewed by Eureka Health Medical Group
Published: June 11, 2025Updated: June 11, 2025

Summary

A burst of adrenaline, not your alarm clock, is likely jolting you awake at 3 a.m. The two most common culprits are nighttime anxiety and mild over-active thyroid, but low blood sugar, sleep apnea, medications, or even caffeine after lunch can do the same thing. Check red-flag symptoms first, then ask your clinician for a thyroid panel, fasting glucose, and a sleep study if simple sleep-hygiene fixes don’t stop the episodes within two weeks.

Is it the thyroid, anxiety, or something else when my heart races at 3 a.m.?

Most people who wake abruptly with a fast heartbeat have a surge of stress hormones during the lighter stages of sleep. Anxiety accounts for roughly 45 % of cases, while early hyperthyroidism explains about 15 %. Other metabolic, cardiac, or medication-related issues fill the rest.

  • Anxiety spikes cortisol at 3 a.m.Cortisol naturally rises around this time; in anxious sleepers it can overshoot and push heart rates over 100 bpm.
  • Early hyperthyroidism shortens REM cyclesEven a mildly suppressed TSH (<0.4 mIU/L) can boost resting heart rate by 10-20 bpm during the night.
  • Low blood sugar triggers epinephrineIf your glucose dips below 70 mg/dL, counter-regulatory hormones race the heart to restore fuel to the brain.
  • Certain blood-pressure pills can rebound at nightShort-acting beta-blockers or clonidine may wear off by 3 a.m., letting adrenaline surge.
  • Quote from the experts“In clinic we find that one simple question—‘Do you feel tense before bed?’—helps separate anxiety from thyroid causes in 80 % of cases,” says the team at Eureka Health.
  • Sleep apnea’s oxygen dips jolt the heartTri City Cardiology warns that the paused breathing of sleep apnea can “cause surges of adrenaline that wake you with a pounding heart,” making it a hidden culprit of 3-a.m. palpitations. (TCC)
  • Evening caffeine and alcohol prime palpitationsHealthline lists stimulants such as caffeine, nicotine, and alcohol among the leading triggers for nighttime heart palpitations, especially when consumed close to bedtime. (Healthline)

References

When does a 3 a.m. racing heart signal an emergency?

Most midnight palpitations are benign, but certain patterns suggest a serious cardiac or endocrine problem. Seek immediate care if any red-flag sign appears.

  • Heart rate stays above 120 bpm for 30 minutesPersistent tachycardia raises the risk of arrhythmia.
  • Chest pain or pressure accompanies the poundingCould indicate an acute coronary event especially in adults over 40.
  • Feeling faint or actually passing outSyncope can reflect dangerous rhythm problems like SVT or ventricular tachycardia.
  • Shortness of breath or wheezing while lying flatMay signal heart failure or severe hyperthyroidism (thyroid storm).
  • Quote from the experts“If you wake drenched in sweat, dizzy, and can’t catch your breath, call 911 rather than waiting till morning,” advises Sina Hartung, MMSC-BMI.
  • Snoring or gasping during the episodeSleep expert Dr. Alexa Kane warns that being jolted awake with a pounding heart plus loud snoring or gasping can indicate obstructive sleep apnea and should prompt a medical work-up. (Surrey)
  • Waking at 3 a.m. is common but usually harmlessAbout 35 % of Americans wake near 3 a.m. at least three nights a week, mainly because an early-morning cortisol surge can spike heart rate and anxiety—episodes without other red flags are rarely dangerous. (KB)

References

What harmless habits can make your heart pound at night?

Everyday choices often raise nighttime heart rate more than disease does. Tweaking these can stop episodes within days.

  • Late-day caffeine lingers six hoursA double espresso at 4 p.m. keeps half its stimulant power at 10 p.m.
  • Alcohol fragments REM sleepTwo drinks can increase midnight heart-rate variability by 20 % and provoke awakening.
  • Phone screens suppress melatoninBlue light after 9 p.m. delays sleep onset and spikes sympathetic activity.
  • Over-warm bedrooms raise heart rateSleeping above 70 °F (21 °C) increases basal heart rate by about 5 bpm.
  • Quote from the experts“Switching from wine to herbal tea after dinner stopped palpitations for one out of three patients in our pilot program,” notes the team at Eureka Health.
  • Sugary snacks spike adrenalineA high-sugar dessert before bed can create a blood-glucose swing that “your body interprets as stress,” triggering an adrenaline rush and a pounding heart. (HL)
  • Bedtime nicotine jolts the heartCleveland Clinic lists nicotine among the most common nighttime palpitation culprits because the stimulant rapidly activates the sympathetic nervous system and elevates pulse. (CC)

References

What can I do tonight to calm my heart and stay asleep?

Simple, evidence-based steps lower nocturnal adrenaline and stabilize heart rhythm.

  • 4-7-8 breathing slows the pulseIn a 2022 study, exhalation-focused breathing cut heart rate by 14 bpm within 60 seconds.
  • Keep glucose steady with a protein snackA small handful of nuts at 9 p.m. prevented hypoglycemia-related palpitations in 70 % of people with night sweats.
  • Lower room temperature to 65-68 °FCool sleep environments increase deep-sleep time and reduce sympathetic surges.
  • Schedule worry time before bedWriting anxieties down at 9 p.m. cut nocturnal awakenings by 35 % in a randomized trial.
  • Quote from the experts“Patients who pair diaphragmatic breathing with a cooler bedroom often notice results by the third night,” says Sina Hartung, MMSC-BMI.
  • Screen for nocturnal panic attacksAs many as 7 in 10 people with panic disorder also wake with sudden racing heart and sweating, so recognizing a possible nocturnal panic attack can ease worry and guide treatment choices. (CC)
  • Gentle Valsalva can reset your rhythmHealthline lists vagal maneuvers—holding your breath and bearing down—for a few seconds as a quick way to restore normal heart rate when palpitations strike at night (do this only if your doctor has okayed it). (HL)

References

Which tests and treatments matter for recurrent 3 a.m. palpitations?

If lifestyle fixes fail, targeted labs and, occasionally, medication help pinpoint and ease the problem.

  • TSH, free T4, and total T3 catch subclinical hyperthyroidismA TSH below 0.4 mIU/L with high-normal T4 justifies an endocrinology referral.
  • Overnight oximetry screens for sleep apneaAn oxygen saturation drop >4 % more than five times an hour suggests the need for a polysomnogram.
  • Continuous glucose monitor spots nocturnal lowsValues under 70 mg/dL correlate with adrenaline-driven awakenings.
  • Extended Holter or patch monitors arrhythmiasCaptures atrial fibrillation episodes that an office ECG might miss.
  • Quote from the experts“Don’t jump to a beta-blocker before ruling out untreated hyperthyroidism—masking the symptom can delay the cure,” warns the team at Eureka Health.
  • Echocardiogram rules out structural heart issuesMayo Clinic guidelines advise an echo when palpitations persist despite normal rhythm strips, because ultrasound can detect valve disease or cardiomyopathy that trigger night-time racing. (Mayo)
  • CBC and electrolytes catch hidden triggersAccording to AACSM cardiologist Lee Surkin, routine blood tests for anemia, electrolyte shifts, and vitamin deficits are part of the first-line workup for nocturnal palpitations. (AACSM)

References

How Eureka Health’s AI doctor can help you sort out midnight palpitations

Eureka’s secure chat lets you describe each episode, upload smartwatch heart-rate graphs, and receive a clinician-reviewed action plan within hours.

  • Symptom triage in under five minutesThe AI asks targeted follow-up questions to flag emergency patterns.
  • Lab and monitor ordering at your paceIf indicated, the AI suggests a TSH panel or Holter; licensed doctors approve and route orders to your local lab.
  • Medication review catches stimulant side-effectsThe system cross-checks your current prescriptions for drugs known to cause tachycardia.
  • Personalized sleep-hygiene planUsers receive step-by-step bedtime routines based on their triggers.
  • Quote from the experts“Eureka turns raw data—like your 2:57 a.m. step count—into clinically useful patterns clinicians can act on,” explains Sina Hartung, MMSC-BMI.

Why people with nighttime palpitations rate Eureka 4.8⁄5

Users appreciate practical guidance without judgment, plus fast access to human oversight when needed.

  • Privacy-first design keeps sensitive data secureAll chat data are end-to-end encrypted and never sold.
  • One-tap follow-up with cardiologyIf the AI flags an arrhythmia, a board-certified cardiologist reviews the case the same business day.
  • Progress tracking shows trendsThe app graphs nightly heart-rate spikes, helping users see improvement after lifestyle changes.
  • High satisfaction among women 30-55In a 2024 survey, women with perimenopausal palpitations rated Eureka 4.8 out of 5 for usefulness.
  • Quote from the experts“Patients feel heard because the AI never shrugs off a 3 a.m. message—it answers instantly,” notes the team at Eureka Health.

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Frequently Asked Questions

Can low iron cause my heart to race at night?

Yes. Iron-deficiency anemia forces the heart to pump faster to deliver oxygen. A ferritin test below 30 ng/mL can explain palpitations.

Will cutting out caffeine completely stop the episodes?

If caffeine is your main trigger, palpitations often improve within 7–10 days of total avoidance, but other causes may still need attention.

Are smartwatch ECG readings reliable at 3 a.m.?

They can detect arrhythmias like atrial fibrillation with about 90 % specificity, but a medical-grade Holter is more accurate.

Does magnesium before bed help?

A small study showed 300 mg of magnesium glycinate reduced nighttime PVCs, but always ask your clinician before starting supplements.

Can menopause trigger 3 a.m. palpitations?

Yes. Fluctuating estrogen increases sympathetic tone, and up to 40 % of perimenopausal women report nocturnal heart racing.

How long should I try lifestyle changes before seeing a doctor?

If episodes persist longer than two weeks or worsen despite good sleep hygiene, schedule a professional evaluation.

Is it safe to take over-the-counter sleep aids for this?

Some antihistamine-based sleep aids can actually raise heart rate; consult a clinician before using them.

Could beta-blockers taken at night solve the problem?

They often slow the heart but may mask the root cause. Only start them under medical supervision after proper testing.

This content is for informational purposes only and is not intended as medical advice. Always consult with a qualified healthcare provider for diagnosis, treatment, and personalized medical recommendations.

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