Diagnosis and Tests for Diabetes Mellitus

Diabetes diagnosis is simple, cheap and exact - a blood test, not a guess. Here are the numbers that define it and the tests that track it.

The diagnostic tests

• Fasting plasma glucose: 8 hours without eating, then blood drawn. Normal under 100 mg/dL; 100-125 is prediabetes; 126 or above, confirmed on a second occasion, is diabetes
• HbA1c: the 3-month sugar average - no fasting needed. Under 5.7% normal; 5.7-6.4% prediabetes; 6.5% or above is diabetes. Also the main control-tracking test - most adults with diabetes aim for around 7%
• Oral glucose tolerance test (OGTT): fasting sugar, then a measured glucose drink, then a 2-hour reading - 200 mg/dL or above at 2 hours is diabetes. The standard test in pregnancy (screening around 24-28 weeks)
• Random plasma glucose: 200 mg/dL or above WITH classic symptoms (thirst, urination, weight loss) is diabetes - no second test needed

The tracking tests (after diagnosis)

• HbA1c every 3-6 months: the report card
• Home glucose monitoring: fasting and post-meal readings as advised - essential for insulin users, useful for many on tablets
• Urine albumin and kidney function yearly: catches kidney involvement early
• Dilated eye examination yearly: catches retinopathy while it is still treatable
• Foot examination at every visit: sensation, circulation, skin

Who should test and when

• Everyone over 30-35: a baseline sugar test, then yearly if risk factors (family history, belly fat, sedentary work)
• Pregnant women: universal screening mid-pregnancy
• Anyone with classic symptoms: test this week, not someday

One-line summary

Diabetes is diagnosed by numbers - fasting 126, HbA1c 6.5%, OGTT 2-hour 200, or random 200 with symptoms - and managed by tracking: HbA1c every few months, and yearly kidney, eye and foot checks that catch complications while they are still reversible or stoppable.