Keto and Heart Palpitations: Causes and Fixes

Few side effects of a new diet are as unsettling as feeling your own heart. A flutter, a skipped beat, a short run of pounding while you are sitting still: it is alarming in a way that a bit of tiredness never is, and it sends plenty of new keto dieters straight to a search engine at two in the morning. The reassuring headline is that palpitations in the early weeks of keto are common, usually harmless, and almost always traceable to one fixable cause. Here is what is going on and how to settle it, along with the signs that mean you should stop reading and ring a doctor.

What a palpitation actually is

A palpitation is simply an awareness of your own heartbeat when you would not normally notice it. People describe it as fluttering, thumping, racing, flip-flopping, or a single hard thud followed by what feels like a pause. Most of the time these are ordinary variations in heart rhythm that everyone has, including extra beats the heart throws in now and then. On a normal day you do not feel them. Something about being on keto makes some people suddenly very aware of them, and that something is mostly about minerals and water.

Why keto sets the heart fluttering

When you cut carbohydrate, your insulin levels fall. Low insulin tells the kidneys to let go of sodium, and sodium leaves the body with a fair amount of water attached. This is the same mechanism behind the rapid “whoosh” of weight people drop in week one, and it is the root of the keto flu too. The trouble is that as sodium goes, potassium and magnesium tend to follow, and those two minerals are exactly the ones your heart’s electrical system relies on to keep a steady beat. Drop them low enough and the heart becomes twitchy, firing off extra beats you can feel. Add in the mild dehydration from all that lost water, and the stage is set for palpitations.

There is a second thread worth knowing. Early keto can nudge up stress hormones like adrenaline and cortisol while the body learns to run on fat, as the piece on stress and cortisol explains, and adrenaline makes the heart beat harder and faster. Between the mineral shortfall and the hormonal shuffle, a fluttery heart in the first fortnight is less a warning sign than a predictable part of the adjustment for some people.

The electrolyte shortfall behind most of it

If palpitations have a single culprit on keto, it is low electrolytes, and of the three the two that matter most for heart rhythm are potassium and magnesium. These are not minerals you can afford to guess at. A rough daily target that works for many people is around 3,000 to 5,000 mg of sodium, 3,000 to 4,000 mg of potassium, and 300 to 400 mg of magnesium, spread across the day rather than taken in one hit. The full detail, including how to hit those numbers from food rather than pills, lives in the guide to getting your electrolytes right, and the broader overview of electrolytes on keto is worth a read if this is all new.

In practice that looks like salting your food properly and without guilt, drinking a cup of broth or salted water when you feel off, and leaning on potassium-rich keto foods such as avocado, spinach, salmon and mushrooms. Magnesium is the one most people fall short on even off keto, so a supplement in the evening, magnesium glycinate or citrate rather than the cheap oxide, is a sensible move. For which forms and doses are worth bothering with, see the rundown of vitamins and minerals to watch.

Caffeine turns the volume up

If your heart is already a little twitchy from low minerals, caffeine will happily make it worse. Coffee, strong tea, energy drinks and pre-workout powders all stimulate the same system that adrenaline does, and keto can change how sharply you feel caffeine once your usual carby buffer is gone. I am not going to tell anyone to give up their coffee, but if palpitations have started, a few days of cutting back, switching to decaf after midday, and seeing whether the flutters ease is a cheap and quick experiment. The article on caffeine and keto goes further into why the two interact. Alcohol deserves the same suspicion, since it both dehydrates you and can trigger extra beats of its own.

When it tends to happen, and for how long

The classic pattern is palpitations that show up in the first one to three weeks, peak somewhere around the time the keto flu would, and fade as the body adapts and you get the minerals under control. For most people they are a passing feature of the transition rather than a permanent fixture. If you have been on keto for months and palpitations appear out of nowhere, that is a different situation and more worth investigating, because it is less likely to be simple adaptation and more likely to be either a slip in your electrolyte habits or something unrelated to the diet entirely.

A simple plan to settle them

Try this before anything more dramatic. Add half a teaspoon of ordinary salt to your day across meals and drinks. Take a magnesium supplement in the evening. Eat a potassium-rich food at every meal. Drink enough that your urine is pale, without drowning yourself in plain water, which can actually dilute your sodium further. Ease off caffeine and alcohol for a week. Give it several days, because minerals take a little while to top back up. The great majority of keto palpitations respond to exactly this, and quickly enough that you will usually know within a few days whether minerals were the problem.

When palpitations mean see a doctor

This is the part not to skim. Electrolyte-driven flutters are one thing; some symptoms are not to be managed with broth and patience. Seek medical advice promptly, and urgently if they come together, for palpitations that are accompanied by chest pain or pressure, breathlessness, fainting or near-fainting, dizziness that does not pass, or a fast beat that will not slow down and lasts more than a few minutes. The same applies if you have a known heart condition, and if you take medication, since keto can change how some drugs behave, as the note on keto and your medications explains, and blood-pressure and diuretic medicines in particular interact with the very mineral shifts described here. Palpitations that keep returning despite good electrolytes also warrant a proper look, if only to rule things out. A doctor can check your bloods and run a simple heart trace, and that reassurance is worth having.

The bottom line

A racing or fluttering heart in the early weeks of keto is common, usually down to the sodium, potassium and magnesium your body sheds along with water, and often made worse by caffeine. Salt your food, top up potassium and magnesium, stay sensibly hydrated, and go easy on the coffee, and most people find the flutters settle within days. Keep a clear line in your head, though: anything that comes with chest pain, breathlessness or fainting, or that will not stop, is a reason to get checked rather than a reason to reach for the salt.

This is general information about the ketogenic diet, not medical advice. Keto does not suit everyone; if you are pregnant, on medication, or managing a condition such as diabetes or a heart problem, speak to a doctor or dietitian first.