Interpreting Diabetes Measures & Laboratory Data

A1C and Estimated Average Glucose

A1C reflects average blood glucose over roughly the prior two to three months and is the anchor lab value for both diagnosis and ongoing management. Because most people relate more easily to the glucose numbers they see on a meter or CGM than to a percentage, the ADA publishes a validated conversion — drawn from the international A1C-Derived Average Glucose (ADAG) study — that translates A1C into an estimated average glucose (eAG) in mg/dL:

eAG (mg/dL) = (28.7 × A1C%) − 46.7

Use this table when teaching: telling someone their A1C of 8% corresponds to an average glucose of roughly 183 mg/dL over the last few months makes the abstract percentage concrete and actionable. A1C has limits worth knowing — it can be falsely low or high with conditions that alter red blood cell turnover (hemolytic anemia, recent transfusion, pregnancy, certain hemoglobinopathies) — so when A1C and self-monitored glucose or CGM data disagree substantially, investigate rather than default to the A1C. When CGM data is available, Time-in-Range and the CGM-derived Glucose Management Indicator (GMI) supplement A1C with a fuller picture of variability, since two people can share an identical A1C while one has stable readings and the other swings widely between hypoglycemia and hyperglycemia — a distinction A1C alone cannot show.

Lipid Panel

Diabetes is itself an ASCVD risk-enhancing condition, so lipid management is a core part of assessment. A lipid panel is obtained at diagnosis, annually thereafter, and again 4–12 weeks after starting or adjusting lipid-lowering therapy. Statin intensity and the LDL cholesterol goal both depend on whether the person already has established atherosclerotic cardiovascular disease (ASCVD):

For adults 40–75 with diabetes and no ASCVD, moderate-intensity statin therapy is added to lifestyle management; for adults with diabetes and established ASCVD, high-intensity statin therapy is recommended, with ezetimibe or a PCSK9 inhibitor added if the LDL goal is not reached on maximally tolerated statin therapy.

eGFR and UACR: Staging Kidney Involvement

Diabetes is a leading cause of chronic kidney disease, so both estimated glomerular filtration rate (eGFR) and urine albumin-to-creatinine ratio (UACR) are checked at least annually in everyone with diabetes — more often once CKD is established. The two values are read together, not separately, because at any given eGFR the degree of albuminuria independently predicts CKD progression, cardiovascular risk, and mortality.

eGFR stage (mL/min/1.73 m²):

UACR albuminuria category:

A person can have a normal eGFR and still have clinically significant kidney disease if albuminuria is elevated — an A2 or A3 result at a "normal" G1/G2 eGFR still warrants ACE inhibitor/ARB or additional cardiorenal-protective therapy discussion, not reassurance. G1 and G2 are only classified as CKD when accompanied by markers of kidney damage such as albuminuria; a normal eGFR with a normal UACR reflects no CKD.

Liver Enzymes

Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) are checked at baseline and periodically thereafter; typical laboratory reference ranges run roughly 7–56 U/L for ALT and 10–40 U/L for AST, though the exact upper limit varies by laboratory and reference population. Liver enzymes matter in diabetes care for several practical reasons: nonalcoholic fatty liver disease (now more commonly termed metabolic dysfunction-associated steatotic liver disease, MASLD) is common in type 2 diabetes and often first surfaces as mildly elevated ALT; several diabetes medications carry hepatic considerations (pioglitazone is avoided in active liver disease; statins are monitored, though routine repeat LFT testing is no longer required once therapy is stable); and metformin requires caution rather than automatic avoidance in the setting of significant hepatic impairment because of a theoretical lactic-acidosis risk. A CDCES uses an elevated ALT/AST not as an isolated number but as a prompt to review the full medication list, alcohol history, and metabolic risk profile alongside it, and to reinforce that the same lifestyle interventions taught for glycemic control — weight management, activity, and limiting added sugar and alcohol — are first-line therapy for MASLD as well.

Bringing the Data Together

None of these values is interpreted in isolation. A person with an A1C corresponding to an eAG well above target, an LDL above goal, an A2 UACR, and a mildly elevated ALT is not four separate problems — it is one picture of insulin resistance and cardiometabolic risk that should drive one coordinated conversation about medication selection, nutrition, and activity, which is exactly the connective role Domain II plays after this Domain I data-gathering step.