I was diagnosed with major depressive disorder for years and it didn't change to bipolar until I had a major manic episode. You have to have been at both ends of the pole major depression and manic. It usually happens in cycles with periods of stable moods in between. It is not just a little moody like adel_ezz said it can be crippling because it is so extreame.
Depression;
*loss of interest in daily activities
*feelings of hopelessness
*loss of appetite or increase in appetite
*sleeping too little or too much
*become withdrawn from friends and family
*irritability
*thoughts of death and suicide
*attempted suicide
*tearful
*inability to concentrate
*decreased energy and motivation
*delusional thoughts
Mania;
*euphoria or irritability
*racing thoughts
*sleeping very few hours or not at all
*Grandiose or inflated self esteem
*increased sex drive
*shopping sprees
*engaging in risky behavior
*become more goal oriented
*inability to concentrate
*increased energy
*delusional thoughts hallucinations or other forms of psychosis
Here is a brief overview of some symptoms. Note these symptoms effect your daily life, because they are so extreme. For example you don't bathe for a week or do your dishes for a month, or get fired from your job, become thousands of dollars in debt due to shopping sprees, etc.You can always do a google search for bipolar to get more information.
How does a pregnant woman know she will deliver a baby, her neighbors will tell her. It's easy she will start to scream and suffer meaning she feels the labor with its heavy contractions.
Had it been like schizofriendia said: if you're feeling depressed half the time and then elated the other half of the time, then I wouldn't be worried at all.
Bipolar disorder has more than that, much much more. Otherwise you are simply moody and you bear it a bit until your mood switches over.
In BP depression means real depression NOT mood but clinically depressed you are crippled in terms of mood and energy, you may commit suicide while in mood elation you eat like the devil sleep much less can have hallucinations and psychosis you lose connection. Among this you have comorbid issues like being tense to the point you can't concentrate you feel lost with total anxiety.
Again there are cases where one phase may last for years not just cycling all the time. In my case my bipolar mania started after 6 years due to an antidepressant.
Don't go to a pdoc unless you start not functioning due to your serious mood change. If you you go to see one for a change then you may risk being put on a drug due to which you are imprisoned for life in this business.
Bipolar disorder is not just a moody behavior rather a serious mental illness that manifests itself in mood among other things.
DON'T fetch for trouble until trouble search you
It's a good indicator if you're feeling depressed half the time and then elated the other half of the time.