What Causes Blood Sugar to Fluctuate? Blood sugar (glucose) levels naturally rise and fall throughout the day, but excessive fluctuations can lead to health issues such as fatigue, irritability, insulin resistance, or even diabetes over time . Understanding what causes these changes can help you better manage your blood sugar and maintain stable energy levels. Food Choices The most immediate and significant cause of blood sugar fluctuation is diet, specifically, the types of carbohydrates you consume. Simple carbs (like white bread, candy, and sugary drinks) cause a rapid spike in blood sugar, followed by a crash. Complex carbs (like oats, brown rice, and legumes) are digested more slowly, leading to a gradual rise in glucose. Skipping meals or irregular eating can also cause your blood sugar to drop, followed by overeating, which spikes it again. Physical Activity Exercise helps muscles use glucose for energy, which can lower blood sugar levels. Moderate exercise helps maintain...