The condition that the left side of the testicle is large and the right side is small is recommended to be checked at the hospital. Because the size of bilateral testicles is different at different ages, an ultrasound can determine whether it is within the normal range according to the age. If you are an adult, the majority of bilateral testicles are not normally large in size, but the difference is not significant. Be careful to determine if there is pain in both testicles. If one testicle becomes larger and there is pain, this may be an inflammation of the testicle. If one testicle is normal and the other side is significantly smaller, this may be a result of testicular dysplasia on this side, or the testicles may have descended too late, causing the testicles to not undergo normal development. A sex hormone test and testicular ultrasound should be done to assess the function of the testicles.