Heart palpitations and racing heart after drinking alcohol are extremely common — and usually harmless, though occasionally they signal something more serious. Understanding why alcohol affects your heart rate helps you know when to worry and when to relax. Alcohol causes tachycardia (elevated heart rate) through several mechanisms. First, it's a vasodilator — it relaxes blood vessel walls, causing blood pressure to drop slightly. Your heart compensates by beating faster to maintain blood flow. A single drink can increase heart rate by 5–10 beats per minute; 3–4 drinks may raise it by 15–25 bpm (European Heart Journal, 2017). Second, alcohol triggers the release of catecholamines — stress hormones including adrenaline and noradrenaline. These increase both heart rate and the force of heart contractions. This is especially pronounced during the hangover phase, when your body is metabolizing acetaldehyde and cortisol levels are elevated. Third, dehydration from alcohol's diuretic effect reduces blood volume, forcing the heart to pump faster to circulate the same amount of oxygen. The more serious concern is alcohol's link to atrial fibrillation (AFib) — an irregular heart rhythm that affects the upper chambers. A landmark 2021 study in the European Heart Journal found that even moderate drinking (1.2 drinks/day on average) increased AFib risk by 16%. The phenomenon is well-known enough to have a clinical nickname: "holiday heart syndrome," describing AFib episodes triggered by binge drinking during holidays or celebrations. When to be concerned: occasional palpitations during or after drinking that resolve within hours are typically benign. However, if you experience chest pain, shortness of breath, fainting, or palpitations lasting more than several hours, seek medical attention. People with pre-existing heart conditions should discuss alcohol use with their cardiologist. Sources: European Heart Journal (2017, 2021), American Heart Association, NIAAA "Alcohol and the Heart."