Bipolar disorder is quite a common mental health disorder- a large part of the Indian population suffers from it. The symptoms can start as early as the teenage years (or in some cases even earlier) and generally can show even when the person is in their 30s. An accurate diagnosis can be made only after certain laboratory tests are done, a comprehensive psychiatric and medical history, observable behavior, self-testimonials, and testimonies of others (family and loved ones) are taken into account.
There are certain things you can be on the lookout for as far as early symptoms count, which can be on you or a loved one around you. If you feel sad, hopeless, or irritable for a long amount of time, if you are lacking energy, have difficulty concentrating and remembering things, lost interest in things, and have negative feelings such as emptiness, worthlessness guilt, despair being around you- then you should each out and get the help that you need.