Fasting glucose is the sugar in your blood after an overnight fast. It moves with last night's dinner, a poor sleep, or an early walk. HbA1c reflects the sugar attached to haemoglobin over the life of a red cell, roughly three months. It does not need fasting.
A normal fasting sugar with a high HbA1c happens. So does the reverse. Doctors use the pair, and sometimes a post-meal sugar, before they use the word diabetes or prediabetes.
Conditions that change red cell life, such as some anaemias, can shift HbA1c. Mention them when you book a counselling call.
This article explains how tests are used. It is not a personal diagnosis.