Why sometimes pulse rate above 100 in rest time?

A pulse rate above 100 beats per minute at rest, known as tachycardia, can occur for various reasons. Common causes include stress, anxiety, dehydration, fever, or an overactive thyroid. Certain medications, stimulants like caffeine, and underlying medical conditions such as anemia or heart disorders can also contribute. It's important to monitor persistent elevated heart rates and consult a healthcare professional if they occur frequently.