Chicken thighs need to reach a specific temperature during cooking to ensure that all harmful bacteria have been killed and the meat is cooked through. Checking the appearance and color of meat is not an accurate or safe method to use to ensure doneness. You will find that in some cases, meat will appear done and yet it has not reached the proper internal temperature. When cooking chicken -- particularly thigh meat -- you should never use the "eyeball" method. Instead, check the internal temperature with a meat thermometer.
Remove one chicken thigh from your cooking surface using a pair of tongs or other cooking implement.
Pierce the chicken thigh with a meat thermometer in the thickest portion of the thigh. Ensure the thermometer is not touching bone.
Watch the thermometer until the dial stops moving or, if using a digital thermometer, the numbers cease to rise. If the internal temperature is lower than 165 degrees F, continue cooking the chicken until it reaches the proper internal temperature.