This is one simple test that you can do from your home that will tell you a lot about your health. It is best to do it in the morning before you have your breakfast and also you should not drink water before.
All you have to do is take one spoon and then rub it on your tongue until it gets all wet of the saliva. Then take a plastic bag and put the spoon inside and put it under sunlight or other bright light. Keep it for one minute and then take it out of the bag.
You have a good health if there is no odor or stains on the spoon. However, if there is a smell of ammonia that may mean problems with the kidneys. If the smell is some kind of fruity then the reason may be diabetes.
If there is a white stain on the spoon, that may mean a problem with the respiratory system. If the stain is purple then the reason is your poor blood circulation, high cholesterol level or maybe bronchitis.
If the stains are yellow and with a tick coating it indicated a problem with the function of the thyroid gland.
And lastly, if they are orange then they are indicating to a kidney issue.