Diabetes Mellitus Initial Assessment

Clinical Presentation

Patients with diabetes mellitus usually present with polyuria, polydipsia, and unexplained weight loss. Most patients with type 1 diabetes present with ketoacidosis or acute onset of hyperglycemia. Other patients have presentations similar to type 2 diabetes. Patients may have a late onset and slow disease progression. Patients may also have other autoimmune disorders (eg Graves’ disease, Hashimoto’s thyroiditis, Addison’s disease).  

The majority of type 2 diabetes mellitus patients are asymptomatic. Ketoacidosis is uncommon and usually secondary to stress (eg infection). Patients may remain undiagnosed until complications have appeared. Hyperglycemia develops gradually and during the early stage, symptoms are often not severe enough for the patient to recognize.

History

The following are the important components of medical history:

• Age and symptoms of diabetes mellitus at the onset
• Lifestyle of the patient (eg eating habits, physical activities, nutritional status, and weight history)
• History of weight loss
• History of diabetes mellitus education
• History of recurrent hypoglycemia
• Current and previous treatment regimen and corresponding response (based on HbA1c records) including patient’s glucose monitoring result
• Frequency, severity, or cause of diabetic ketoacidosis
• Incidence, cause, and severity of hypoglycemia, and patient’s awareness
• History of diabetes mellitus-related complications including retinopathy, nephropathy, coronary heart disease (CHD), cerebrovascular disease, peripheral arterial disease (PAD)
• Current or history of skin, foot, dental, and genitourinary (GU) infections
• History of drug or alcohol use
• Occupational history

Physical Examination

A complete physical examination should be done which includes:

• Height, weight, body mass index (BMI), and waist measurement
• Blood pressure (BP) including orthostatic measurement if appropriate
• Thyroid palpation/status
• Skin examination to check for acanthosis nigricans and insulin injection sites
• Neurological examination
• Cardiovascular system, chest, and abdominal examinations
• Fundoscopic examination
• Complete foot examination

Please see Screening and Management of Diabetes Mellitus Complications or Comorbidities discussion for further information.

Diagnosis or Diagnostic Criteria

Diabetes mellitus is diagnosed without further testing in patients presenting with unequivocal hyperglycemia with acute metabolic decompensation (eg diabetic ketoacidosis [DKA], hyperosmolar non-ketotic hyperglycemic coma).  

The same tests are used for screening and diagnosis. Diagnosis of diabetes mellitus is based either on fasting plasma glucose (FPG), a 2-hour value in the 75-g oral glucose tolerance test (OGTT), or glycosylated hemoglobin A1c (HbA1c) in which a single abnormal value is diagnostic for a symptomatic individual. HbA1c levels may vary with the patient’s ethnicity, presence of anemia, or hemoglobinopathy. Diagnosis should also be based solely on plasma blood glucose criteria in patients with abnormal red cell turnover (eg pregnancy, recent blood loss or transfusion, sickle cell disease, hemodialysis). Patients with established cardiovascular disease should be screened using fasting plasma glucose and/or HbA1c, however, an oral glucose tolerance test may be done if fasting plasma glucose and HbA1c are inconclusive.  

A diagnosis of diabetes mellitus can be given if any of the following is present:

• HbA1c level of ≥6.5% (48 mmol/mol)*
  • The test should be performed in a laboratory using a national glycohemoglobin standardization program (NGSP) certified method and standardized to Diabetes Control and Complications Trial (DCCT) assay
• FPG of ≥7 mmol/L (≥126 mg/dL)
  • Fasting is considered as no caloric intake for at least 8 hours
• 2-hour plasma glucose of ≥11.1 mmol/L (≥200 mg/dL) during OGTT
  • Performed using a glucose load that contains the equivalent of 75-g anhydrous glucose dissolved in water
• Random plasma glucose of ≥11.1 mmol/L (≥200 mg/dL) in a patient presenting with hyperglycemic crisis or classic symptoms of hyperglycemia

If typical hyperglycemic symptoms are not present, diagnosis requires two abnormal test results from the same sample or in two separate test samples. If two different tests are available and are both above the diagnostic thresholds, the diagnosis of diabetes is made. If two different test results are discordant, the test whose result is above the cut-off point should be repeated and the diagnosis is made based on the result of the confirmatory test.

Pre-diabetes is considered in patients with the following:

• Impaired fasting glucose (IFG): FPG of 5.6-6.9 mmol/L (100-125 mg/dL)
• Impaired glucose tolerance (IGT): 2-hour plasma glucose of 7.8 to 11 mmol/L (140-199 mg/dL) in the 75-g OGTT
• HbA1c of 5.7-6.4% (39-47mmol/mol)
  • HbA1c of 6-6.5% have a 25-50% 5-year risk of developing diabetes mellitus
  • Baseline HbA1c is a stronger predictor of subsequent diabetes mellitus and cardiovascular events

*Recommendations may vary between countries. Please refer to available guidelines from local health authorities.

Screening

Screening for diabetes mellitus is recommended for all adults who are overweight (body mass index of ≥23 kg/m² for Asians) or with a waist circumference of ≥80 cm for Asian women and ≥90 cm for Asian men plus the following other risk factors: 

• Physical inactivity
• Diabetes mellitus in a first-degree relative
• Female diagnosed with gestational diabetes mellitus (GDM) or who gave birth to a baby weighing >9 lb (>4 kg)
• Females diagnosed with polycystic ovarian syndrome (PCOS)
• With severe obesity, acanthosis nigricans, or other conditions associated with insulin resistance
• With hemoglobin A1c (HbA1c) ≥5.7%, impaired glucose tolerance (IGT), and impaired fasting glucose (IFG) on previous testing
• With high-density lipoprotein cholesterol (HDL-C) level of 0.9 mmol/L (<35 mg/dL) and/or triglyceride (TG) level of 2.82 mmol/L (>250 mg/dL)
• Diagnosed with hypertension (≥130/80 mmHg) or on antihypertensive drugs
• With a history of cardiovascular disease (CVD)
• Race/ethnicity that is at high risk (eg Chinese, Indians, Asian Americans, African Americans, Latinos, Pacific Islanders)
• With schizophrenia and/or severe bipolar disease on antipsychotic therapy
• Those receiving antiretroviral therapy or long-term systemic steroid therapy
• Those born from mothers with gestational diabetes mellitus

It must be noted that autoantibody screening for presymptomatic type 1 DM should be done for those with a family history of type 1 diabetes. According to the American Diabetes Association (ADA) 2024 recommendations, screening for diabetes mellitus in all patients should begin at age 35 years*. Patients should be screened for diabetes within 3-6 months after an episode of acute pancreatitis. Patients with chronic pancreatitis should be screened for diabetes annually.  

HbA1c, FPG, or a 2-hour 75-g OGTT test may be used to diagnose diabetes mellitus or to identify future risks for diabetes mellitus. Testing should be repeated every 3 years if results are normal and may be more frequent depending on the initial results and risk status. Annual screening should be done in patients with pre-diabetes.  

Referral to other specialties should be done for annual dilated fundoscopic examination, family planning in women of reproductive age, medical nutrition therapy (MNT), diabetes self-management education (DSME), dental examination, and mental health assessment, if necessary. Screening for depression, diabetes mellitus-related distress, anxiety, eating disorder, and cognitive impairment should be considered in patients with poor self-management.  

*Recommendations may vary between countries. Please refer to available guidelines from local health authorities.

Diabetes Mellitus_Initial Assesment