Should I have my daughter checked for diabetes? 3yr old has excessive thirst, frequent urination, and vision problems. Took one fastingblood glucose87

See your Pediatricia. Those frequently are symptoms of diabetes, but with fasting glucose of 87, doubt it. See your pediatrician and voice your concerns.
No. If she is 3 years old and has continuing excessive thirst and frequent urination, the sugar of 87 rules out type i diabetes of acute onset. However, the symptoms need to be investigated in other ways.
Please check. Your daughter may have diabetes, but definitely needs to be checked. Those symptoms may be diabetes, but could be symptoms of other conditions. Checking one fasting glucose would not be diagnostic; please see your pediatrician.