I am looking to apply for a 3rd class medical at some point this year. I am in my mid 30s, athletic (runner) in excellent health overall and normal BMI. The only issue I can see is my latest physical had an A1C result come back at 5.7 (prediabetes range). This is up from 5.6 the last time. Apparently this is common in my family as I have relatives who have sat at around this A1C range for years with no issues. I have tested my glucose and found no unusual spikes. I can eat a massive plate of pasta and be lucky to reach 130 before falling. My fasting glucose was 98 from the same labs the A1C came back from. My personal test showed as low as 82 fasting up to 96 after eating high carb the night before. I have no plan to make any major changes other than continuing to monitor A1C yearly.

I have read that prediabetes is a CACI diagnosis. Are there any hurdles I need to pass or specific documentation an AME will need from my general doctor for this? I want to be as prepared as possible to avoid a deferral. Thanks.
The form asks about diabetes, not prediabetes. So you should be fine there.

Has this to say:

18.k. Diabetes. The applicant should describe the condition to include, symptoms andtreatment. Comment on the presence or absence of hyperglycemic and/orhypoglycemic episodes. A medical history or clinical diagnosis of diabetes mellitusrequiring insulin or other hypoglycemic drugs for control are disqualifying. The Examinercan help expedite the FAA review by assisting the applicant in gathering medicalrecords and submitting a current specialty report. (See Item 48, page 123).
Take a look at the FAA "Prediabetes Disposition Table."

It looks like if prediabetes is not treated with medication, then AME can issue if he/she determines the condition is:
• Under control;
• Current medications are acceptable; and
• The individual has no symptoms that would interfere with flight duties

Not 100% how that determination is made. Maybe others who went through this can chime in.

If prediabetes treated with one (non-insulin) medication is a CACI. You need the "prediabetes status report" and a "current, detailed progress note." Two are more medication would be a deferral for SI.
Diabetes controlled by diet and exercise, and prediabetes not in need of treatment (pharmaceutially) are office issuances.