Hello, Possible reasons for dark spots on the tongue include: 1. black hairy tongue - excess keratin (benign), poor oral hygiene and dry mouth can contribute - confirm with dental clinical exam, but usually on top, not sides and tip 2. trauma causing pooled blood - avoid irritations or contributing habits, stay hydrated 3. melanin, blood vessels, geographic tongue - natural pigmentation or pattern variations, flow of blood vessels can give dark blue shadow - hydration may affect appearance, normal individual anatomy, check blood pressure. Pigment change concern for melanoma. 4. vitamin deficiency/excess - check balance, check iron levels, exposure to heavy metals? 5. bacteria overgrowth coating- thrush, oral yeast infection leaves coating - Acidopholus good choice to maintain balance, Nystatin prescription may be necessary to treat chronic condition. 6. surface change - coating from foods, medications, habits- requires increase in oral care, brushing of tongue, change needed to reduce 7. growths - requires clinical evaluation by dentist, monitor condition and ask dentist. Sudden change is of greatest concern. Systemic condition such as Lupus? A clinical exam by a dentist will give you the best diagnosis. Make sure you practice good daily hygiene inclding brushing your tongue, have a balanced diet and keep well hydrated. Look for any triggers or changes to relate to changes with your tongue s appearance. I am glad to answer more questions with additional details. Thank you for your inquiry.