A low-carbohydrate diet restricts the intake of sugars and starches, prompting the body to shift its primary energy source from glucose to fat. Heart palpitations are the sensation of a racing, pounding, or fluttering heart. This common and often harmless experience can feel alarming, and many people report experiencing it, particularly during the initial phase of dietary change. This occurrence is a widely recognized phenomenon due to several interconnected physiological shifts during the metabolic transition.
The Primary Cause: Electrolyte Depletion
The most direct cause of heart palpitations when beginning a low-carbohydrate diet stems from rapid water loss and subsequent electrolyte depletion. When carbohydrate intake is severely reduced, the body quickly burns stored glucose, known as glycogen. Glycogen is stored in the muscles and liver bound to significant amounts of water, and as these stores are used up, the associated water is flushed out. This leads to a temporary state of diuresis, or increased urination.
This rapid fluid loss is compounded by hormonal changes inherent to carbohydrate restriction. Lowered carbohydrate intake results in a decrease in circulating insulin levels. Lower insulin signals the kidneys to excrete more sodium than usual, which regulates fluid balance. As sodium is lost, other electrolytes follow suit, including potassium and magnesium.
These three minerals—sodium, potassium, and magnesium—are electrically charged particles that coordinate the precise electrical signaling required for a steady heartbeat. Sodium and potassium maintain the electrical gradient across heart muscle cells, governing the heart’s contraction and relaxation cycle. Magnesium helps regulate the flow of these ions across cell membranes, acting as a natural calcium channel blocker. A deficiency in any of these electrolytes can directly disrupt the heart’s electrical stability, manifesting as skipped beats, fluttering, or a racing heart.
Secondary Triggers: Fluid Loss and Stress Hormones
Beyond the specific electrolyte imbalance, generalized fluid loss contributes to palpitations through a change in overall blood volume. The initial rapid loss of water reduces the total volume of blood circulating through the body. The heart must then compensate by increasing its rate and force of contraction to maintain adequate blood pressure and oxygen delivery.
This compensatory mechanism, known as tachycardia, is experienced as a faster or harder heartbeat, which is recognized as a palpitation. The metabolic shift into a fat-burning state can also be interpreted as physiological stress. This transition phase, often called the “keto flu,” can trigger an increased release of stress hormones, specifically adrenaline and cortisol.
The surge in these stress hormones is a natural response to the change in energy supply, but they act as stimulants on the cardiovascular system. Adrenaline directly increases the heart rate and the force of contraction, which can lead to transient palpitations. While typically short-lived, this hormonal stimulation adds to the feeling of a racing or pounding heart during the first few weeks of the diet.
Actionable Steps for Management
The most effective strategy for managing low-carb-induced heart palpitations is proactively replacing lost electrolytes and fluids. Since sodium excretion is significantly increased, increasing salt intake is recommended to restore fluid balance. This can be achieved by adding extra salt to meals or consuming bone broth, which naturally contains sodium and other minerals.
It is also important to pay close attention to the intake of potassium and magnesium, which are often depleted alongside sodium. Foods rich in potassium, such as avocados, spinach, and mushrooms, should be regularly incorporated. Magnesium-rich options like nuts, seeds, and dark leafy greens help stabilize the heart’s rhythm.
Consistent and adequate water intake is necessary to counter dehydration and support electrolyte balance. Drinking plain water, or water with added electrolytes, throughout the day helps maintain blood volume, reducing the need for the heart to pump harder. Introducing the low-carbohydrate restriction gradually, rather than abruptly, allows the body more time to adapt to the metabolic shift. This potentially minimizes the severity of initial symptoms.
Recognizing When to Seek Medical Help
While heart palpitations related to low-carb dieting are generally temporary, certain symptoms warrant immediate medical attention. Any palpitation accompanied by chest pain or significant discomfort requires urgent evaluation, as these may signal a more serious underlying issue.
If you experience shortness of breath, profound dizziness, or feel faint, consult a healthcare professional without delay. Palpitations that do not resolve within the first few weeks of the diet, or that worsen over time, also require a medical check-up.
Individuals with pre-existing heart conditions, diabetes, or high blood pressure should consult a physician before beginning a restrictive diet. These conditions may interact with the physiological changes of a low-carb diet, potentially requiring medication adjustments or specialized monitoring.