Keto Heart Palpitations at Night: The Real Cause and Fix

You wake up at 2:47am with your heart thumping so loud you can hear it in the pillow. Not a normal thump — a heavy, uneven, sometimes-skipping-a-beat thump. You lie there wondering if this is finally The Big One. It isn't.

Heart palpitations at night on keto are one of the most alarming symptoms anyone can have, but they're almost never cardiac. In healthy low-carb eaters they're an electrolyte problem, specifically potassium and magnesium, with sodium pulling the trigger.

What's actually happening

Every heartbeat is a controlled electrical impulse. That impulse is regulated by three minerals moving in and out of your heart cells: potassium, magnesium, and sodium. Get the ratio wrong and the rhythm gets sloppy — extra beats, skipped beats, or a pounding "I can feel every beat" sensation.

On low-carb, insulin drops. Low insulin tells your kidneys to dump sodium. Sodium leaves and takes potassium and water with it. Magnesium — which most people are already low on — falls further because you're peeing more. By week two of strict keto, most people are running low on all three.

Why it happens at 2 or 3am specifically

The pre-dawn cortisol pulse (the same one behind classic 3am wakeups) makes your heart more sensitive to mineral imbalances. During the day your adrenaline is high enough that a little rhythm noise is masked. At 3am your body is quiet — so a small potassium dip that would be silent at 2pm shows up as a pounding pulse.

The fix (usually 2–4 nights)

1. Magnesium glycinate, 300–400 mg, 30–45 minutes before bed. This is the biggest single lever. Glycinate absorbs; oxide doesn't.
2. Potassium chloride ("No Salt" or "Lite Salt"), 1–2 g through the day. A quarter-teaspoon in dinner covers most of the gap.
3. Sodium, 3,000–5,000 mg total. Push the second half of the day — a big pinch of salt with dinner and a small pinch in water at bedtime.

When to see a doctor

Palpitations with chest pain, fainting, shortness of breath, or a family history of arrhythmia are not electrolytes — get seen. But run-of-the-mill low-carb "my heart is thumping at 3am" almost always resolves within a week of getting the three minerals right.