Many people self-medicate because they feel they can't afford the medications that are commonly used to treat bipolar disorder; however, in nearly all cases there is aid available to those with mental illness who need reduced price or free medications.
Others who have bipolar may self-medicate after years of medical care because of frustration stemming from the need to periodically readjust medications - they may feel that since the doctors can't seem to get it right, they can probably "experiment" with it just as well themselves. This is extremely dangerous, though, because even small changes in drugs like Lithium and other drugs can lead to serious episodes or worse. With Lithium, small changes in dosage can lead to hallucinations, severe illness and even death. For this reason Lithium use should always be carefully monitored by a doctor with regular blood tests. If you self medicate incorrectly, you risk your life and you risk your health.
Others "self medicate" by using alcohol or drugs as a way to temporarily relieve their symptoms when they are in the grips of an episode of either mania or depression. Both of these are common responses that can have dangerous or fatal results.
When using drugs or alcohol while suffering a manic or depressive episode, you may temporarily feel better or at least feel like you are "numbing" yourself, but this is only an illusion. In reality you are blurring your sense of reality even further and inhibiting your ability to react properly to the world around even more. Your judgment is severely damaged. Combine this with the lack of common sense found in mania or the sorrow and lack of self-preservation found in depression and you have a recipe for disaster.
In fact, many people who have bipolar disorder aren't diagnosed for years because they are too busy self-medicating with alcohol or drugs and don't seek medical advice. In the meantime, since they aren't being properly regulated, their manic phases aren't being controlled. They are medicating themselves with booze and pills and still going into episodes of wild spending, promiscuous sexual activity and bizarre, risky behavior. They may lose spouses, friends, jobs and their life savings.
People who are depressed and bipolar will self-medicate to keep the depression at bay, but this actually only pushes the depression back temporarily. When it returns it can feel even worse, and will sometimes result in a suicide attempt or, in some instances, a successful suicide.
Obviously, self-medicating with drugs and/or alcohol doesn't work. It doesn't get rid of the symptoms of bipolar disorder, and in many cases they actually make the characteristics of an episode much worse, causing the extremes to be more violent or explosive.
If you don't believe this, take a look at some examples of individuals who were not properly medicated who ended up in extremely bad situations. Some actual stories can be found at http://www.leverageteamllc.com/bipolarnews19/ . These include one where a woman in Palm Desert, CA ran over a man she referred to as, "road kill," during a manic episode. In other stories, two unrelated shootings (one in Portland, ME and the other in Philadelphia, PA) were both tied to bipolar sufferers who weren't properly medicated.
Please don't take your situation into your own hands - you'll be gambling with your own life and the life of others. Self medicating isn't the answer. A licensed, professional doctor's supervision and prescription medication is the only way to adequately control bipolar disorder effectively.