Female, age 35.Excessive thirst, dry mouth, urination. No diabetes, no thyroid, have dental cavities. What can be the reason of dry mouth?

More info needed... Your problem is not due to your dental caries. Do you drink eight glasses of water a day? High salt diet? Medications? How much alcohol a day? Any other medical conditions? You really need to be seen by a local physician for your dry mouth and your dentist for your cavities. Dry mouth will only exacerbate your dental problems.
Measure urine volume. Hi. There is a rare condition where the pituitary water hormone (ADH (vasopressin)) is deficient. As long as your blood glucose is normal, I recommend you collect for volume measurement a 24 hour urine collection. ADH (vasopressin) deficiency, called diabetes insipidus (not to be confused with diabetes mellitus, the high blood sugar condition) is straight forward to diagnose, and would be warranted if 24-h urine volume high.

Related Questions

If I have no diabetes but excessive thirst then what to Diagnosis of my body? I almost can't sleep for dry mouth and excessive thirst.

Should evaluate. Various medications cause dry mouth, which is often perceived as thirst. A rare possibility is diabetes insipidus. In this condition, the kidneys fail to concentrate the urine, creating excessive urination of mostly water. People with this condition need to drink large quantities of water to keep up with losses. Urine and blood testing, usually by a nephrologist, can help make this diagnosis. Read more...
Dry mouth. It could just be dry mouth from mouth breathing . Some medications can cause dry mouth too. Read more...