Prediabetes and Diabetes Type 2: Screening and Making the Diagnosis

Clinical Actions:

Diabetes results when the pancreas cannot respond to or produce insulin, leading to abnormal metabolism of carbohydrates and elevated levels of glucose in the blood and urine. Type 2 diabetes (previously “noninsulin-dependent diabetes” or “adult-onset diabetes”) accounts for 90–95% of all diabetes. Type 2 diabetes is caused by a progressive loss of β-cell insulin secretion, usually associated with insulin resistance. Prediabetes is diagnosed when glucose levels start to rise due to β-cell insulin secretion failure, but diagnostic criteria are not yet met for Type 2 diabetes.

Table of Contents  

Evaluate Patients for Risk Factors

Risk Factors for Type 2 Diabetes (NIDDK)

  • Overweight or obese
    • NIDDK BMI chart (see ‘Primary Sources – Learn More’ below)
      • Not Asian American or Pacific Islander: At-risk BMI ≥ 25
      • Asian American: At-risk BMI ≥ 23
      • Pacific Islander: At-risk BMI ≥ 26
  • ≥45 years
  • Family history of diabetes
  • Race/Ethnicity
    • African American, Alaska Native, American Indian, Asian American, Hispanic/Latino, Native Hawaiian, or Pacific Islander
  • Hypertension (or on therapy for hypertension)
  • Dyslipidemia
  • Personal history of
    • Pregnancy: GDM or macrosomia (BW >4000 g)
    • Physical inactivity
    • Heart disease or stroke
    • Depression
    • PCOS
    • Acanthosis nigricans
    • HIV

Screening and Diagnostic Criteria

Who and When to Screen

ADA

  • Overweight or obesity (BMI ≥25 kg/m2 or ≥23 kg/m2 in Asian Americans) and ≥1 of the following risk factors
    • First-degree relative with diabetes
    • High-risk race/ethnicity (e.g., African American, Latino, Native American, Asian American, Pacific Islander)
    • History of CVD
    • Hypertension (≥140/90 mmHg or on therapy for hypertension)
    • HDL cholesterol level <35 mg/dL (0.90 mmol/L) and/or a triglyceride level >250 mg/dL (2.82 mmol/L)
    • Women with polycystic ovary syndrome
    • Physical inactivity
    • Other clinical conditions associated with insulin resistance (e.g., severe obesity, acanthosis nigricans)
  • People with HIV
    • Screen for diabetes and prediabetes with a fasting glucose test
      • Before starting antiretroviral therapy
      • At the time of switching antiretroviral therapy
      • 3 to 6 months after starting or switching antiretroviral therapy
    • If initial screening results are normal, fasting glucose should be checked annually
  • Patients with prediabetes (A1C ≥5.7% [39 mmol/mol], IGT, or IFG) should be tested yearly
  • Women who were diagnosed with GDM should have lifelong testing at least every 3 years
  • For all other patients, testing should begin at age 35 years
  • If results are normal, testing should be repeated at a minimum of 3-year intervals, with consideration of more frequent testing depending on initial results and risk status

AACE/ACE

  • Begin at age 45 without risk factors
  • Screening based on risk factors: In addition to the above list, AACE/ACE includes the following factors
    • Antipsychotic therapy for schizophrenia and/or severe bipolar disease
    • Chronic glucocorticoid exposure
    • Sleep disorders (e.g., obstructive sleep apnea, chronic sleep deprivation, and night shift occupation) with glucose intolerance
  • Normal glucose values: Every 3 years
  • Consider annual screening for patients with 2 or more risk factors

USPSTF

  • Screen for prediabetes and type 2 diabetes in adults aged 35 to 70 years who have overweight (BMI ≥25) or obesity (BMI ≥30)
  • Clinicians should offer or refer patients with prediabetes to effective preventive interventions
  • Above are Grade B recommendations: Offer or provide this service

Diagnostic Criteria

  • Normal
    • Fasting plasma glucose (FPG) <100 mg/dL (5.6 mmol per L)
    • Oral glucose tolerance test (OGTT) with 75g glucose load
      • 2h (plasma glucose) PG <140 mg/dL (7.8 mmol per L)
  • High Risk for Diabetes (prediabetes)
    • Impaired fasting glucose (IFG): FPG ≥100 to 125 mg/dL (5.6 to 6.9 mmol per L)
    • Impaired glucose tolerance (IGT): 2h PG ≥140 to 199 mg/dL (7.8 to 11.0 mmol per L)
    • A1C 5.7% to 6.4%
    • Note: Patients with prediabetes should be tested yearly
  • Diabetes: Glucose criteria are preferred for the diagnosis of DM
    • FPG ≥126 (7.0 mmol per L) mg/dL
    • OGTT: 2h PG ≥200 mg/dL (11.1 mmol per L)
    • Random PG ≥200 mg/dL (11.1 mmol per L) with the following symptoms of hyperglycemia
      • Polydipsia | Polyuria | Polyphagia | Blurred vision | Weakness | Unexplained weight loss
    • A1C ≥6.5%
    • Note: Always confirm diabetes diagnosis with repeat glucose or A1C testing on another day

SYNOPSIS:

Prediabetes is not a clinical disorder but rather an important risk factor for diabetes and cardiovascular disease. While there are some differences between organizations regarding risk factors for screening and diagnostic cut-offs, all agree as to the importance of identifying those at risk for significant cardiovascular events if diabetes is left untreated. The prognosis for type 2 diabetes varies and is very dependent on glucose control.

KEY POINTS:

Symptoms of Diabetes (related to hyperglycemia)

  • Excessive urination, thirst and hunger 
  • Unexpected weight loss 
  • Increased susceptibility to infections, especially yeast or fungal infections 
  • Weak, tired feeling
  • Dry mouth
  • Blurry vision
  • Deposits of blood, or puffy yellow spots in the retina
  • Decreased sensation in the legs
  • Weak pulses in the feet
  • Blisters, ulcers or infections of the feet 

Complications of Type 2 Diabetes

  • Atherosclerosis
  • Retinopathy 
  • Neuropathy 
  • Nephropathy
  • Dermatologic pathology
    • Infections
    • Feet in particular: Ulcerations with poor healing  

Learn More – Primary Sources:

ADA: Classification and Diagnosis of Diabetes: Standards of Medical Care in Diabetes—2022

AACE/ACE Clinical Practice Guidelines for Developing a Diabetes Mellitus Comprehensive Care Plan

Consensus Statement By The American Association Of Clinical Endocrinologists And American College Of Endocrinology On The Comprehensive Type 2 Diabetes Management Algorithm – 2020 Executive Summary

NIDDK: Risk Factors for Type 2 Diabetes

60-Second Type 2 Diabetes Risk Test

USPSTF: Screening for Prediabetes and Type 2 Diabetes

HIV and Diabetes | NIH