Glucose is used throughout your body for energy. For your body to use glucose, It needs insulin, a hormone produced by your pancreas that helps muscles, fat, and other cells absorb glucose for fuel. When you are pregnant, your body naturally becomes more resistant to insulin, which means more glucose remains in your blood. The Glucose Challenge Screening is a standard preliminary screening test performed between 24-28 weeks to evaluate how your body processes sugar. Exercise affects both glucose and insulin levels, and this Q&A answers a question about whether working out before a glucose test will affect the results.