Your tongue may reveal a lot about your overall health. White tongue can indicate leukoplakia, lichen planus, or oral thrush. A dark and hairy tongue might indicate poor dental hygiene or diabetes. If your tongue is brilliant red, like a strawberry, it might indicate folic acid, vitamin B12, or iron deficiency. Your tongue may reveal a lot about your overall health. White tongue can indicate leukoplakia, lichen planus, or oral thrush. A dark and hairy tongue might indicate poor dental hygiene or diabetes. If your tongue is brilliant red, like a strawberry, it might indicate folic acid, vitamin B12, or iron deficiency.