If you think that you, or a person you care for, may have bipolar disorder, see your doctor. Getting the right diagnosis is the first step to getting good treatments and being able to live a normal life.
Doctors often find it hard to diagnose bipolar disorder.  And you need the right diagnosis to get the right treatment. It can sometimes take people five years to 10 years before they get the right treatment. 
This is partly because people are more likely to visit their doctor when they have depression (a very low mood) than when they have mania (a very high mood).  If your doctor doesn't know that you also get mania, he or she might think you have ordinary depression.
But the treatments for ordinary depression are different from the ones for bipolar disorder. So be sure to tell your doctor about all of your mood problems, not just the times when you feel depressed.
Tests your doctor may do
If your doctor thinks that you might have bipolar disorder he or she will probably send you to a hospital or clinic. There, you will usually see a professional who specialises in mental health conditions. That person may be a psychiatrist, a psychiatric nurse, or a psychologist. You probably won't need to stay in hospital.
One of these professionals may fill out a form or a questionnaire to get some information about what has been happening to you.  This can help tell if you have bipolar disorder.
There aren't any blood tests or scans for bipolar disorder. But you may have tests or scans to check for other medical conditions that can cause mood problems. For example, you might have blood tests to see if your thyroid gland is too active or too sluggish.
Your doctor may also test your blood or urine for illegal drugs. This isn't to get you into trouble. It's because lots of people with bipolar disorder have problems with illegal drugs. If you are using them it may affect your condition and your treatment. So your doctor needs to know about it. 
Questions your doctor may ask
The most reliable way of diagnosing bipolar disorder is to have a psychiatric examination by a psychiatrist.  Normally, your psychiatrist makes the diagnosis after talking to you.
He or she will do an examination called a mental state examination. This is to check if you have mania or depression. During this examination he or she will:
Check how you look and behave
Listen to the way you speak and what you say
Watch how you move
Note how much energy you have
Ask about your mood and how you feel about yourself
Ask about how you are thinking, if your thoughts are racing or coming slowly
Try to work out if you are having beliefs that aren't true (delusions) or seeing or hearing things that aren't there (hallucinations)
If you are having delusions or hallucinations, try to work out if you know what you believe or perceive is not real.