I have a smooth red patch on my tongue , which I notice about 1-2 weeks ago. It is on the right side, near the edge of the tongue. It sound not cause any pain. I have had a canker sore before but this is not like that. I have looked at geographic tongues but mine does not seem to have any outline, which seems characteristic of geographic tongues. I am 22 years old; weigh approx. 50kg; height is 164 cm. I do not suffer from any medical conditions. I have family history of diabetes and heart disease.
Hello and thank you for your question.  Any time you have a red lesion on the side of the tongue that persists longer than a few weeks it is important to have it evaluated in person by a dentist and possibly biopsied.  Oral cancer can occur at any age and is very common on the side of the tongue.  The tried and true method of identification is through biopsy.  Many lesions can appear flat, red and on the side of the tongue.  Highly unlikely that it is cancer at your age, but safe to rule out if it doesn't go away.  Geographical tongue does have a border but not always apparent.  It can also be lichen plans, trauma from an adjacent tooth, chemical burn from medication, new toothpaste, mouth rinse or spicy/citric foods.  I hope this helps you. Best wishes, good health.