The tongue has a coating, which represents the state of digestive function in your body. The coating of the tongue is actually made up of bacteria that reside on the tongue. It is interesting in that most people think they can scrape the coating off of the tongue.
http://www.wholehealthinsider.com/general-health/the-secrets-hidden-in-your-tongue/
Otherwise, if your kidneys didn't concentrate urine during sleep, you would have to wake up to urinate.) After the urinating the first time after waking up, your urine should be light coloured and odorless for the remainder of the day.
https://answers.yahoo.com/question/index?qid=20080806040512AAHUjtJ
As such, you cannot actually remove the bacteria from your tongue just by scraping it. The ideal tongue coating consists of a thin, white film on the surface of the tongue. A thin, white coating indicates that the stomach and digestive system is healthy and functioning in the process of transforming and digesting food.
http://www.wholehealthinsider.com/general-health/the-secrets-hidden-in-your-tongue/
If there is a red tongue with a yellow coating, there is a chronic inflammatory condition in the body. A red, shiny tongue with no coating usually indicates a loss of the body’s ability to regulate and offset thermogenic hormones in the body. This is often seen in women who start menopause and men who use Lupron®.
http://www.wholehealthinsider.com/general-health/the-secrets-hidden-in-your-tongue/
1 Why is my tongue sometimes yellow in the morning? Yellow tongue: Possibly due to debris and bacteria in the mouth and on the tongue overnight. Be sure that your night time oral care includes brushing your tongue gently, but thoroughly.
https://www.healthtap.com/topics/why-is-my-tongue-yellow-in-the-morning
When it comes to cracks in the tongue, this could be a sign of a yeast infection, as well as a biotin deficiency. A cracked tongue is also a symptom of Sjögren’s syndrome. This would be accompanied by a dry mouth, fatigue, joint pain and burning or itching of the eyes.
http://www.wholehealthinsider.com/general-health/the-secrets-hidden-in-your-tongue/
1 You can only upload photos smaller than 5 MB. 2  You can only upload videos smaller than 600MB. 3  You can only upload a photo (png, jpg, jpeg) or a video (3gp, 3gpp, mp4, mov, avi, mpg, mpeg, rm).  You can only upload a photo or a video.
https://answers.yahoo.com/question/index?qid=20080806040512AAHUjtJ
Hot countries in the world happen to have the worst water supplies. Many women walk over 10 miles a day (15 kilometers) just to get water. If you find this website helpful please consider donating some money to one of our charities, Water Aid by going to our discussion forum. It is easier to pay attention to the color of your urine each time you urinate.
https://answers.yahoo.com/question/index?qid=20080806040512AAHUjtJ
Current recommendations for water are 8, eight ounce glasses per day which would equal 64 ounces. This amount should be sufficient for most healthy persons who are not in a hot, humid environment or sweating from physical work or exercise and should drink more water more often.
https://answers.yahoo.com/question/index?qid=20080806040512AAHUjtJ
1 doctor agreed: Yellow tongue: Possibly due to debris and bacteria in the mouth and on the tongue overnight. Be sure that your night time oral care includes brushing your tongue gently, but thoroughly. ...Read more.
https://www.healthtap.com/topics/why-is-my-tongue-yellow-in-the-morning
what causes yellow material on my tongue when i wake up
The causes of yellow material on your tongue when you wake up are debris and bacteria in the mouth and on the tongue overnight. Due to debris and bacteria in the mouth and on the tongue overnight causes yellow material on your tongue.