Diabetes mellitus

Key Information

Appropriate Tests


Laboratory diagnosis is usually based on measurement of fasting Glucose for >7 hours or random glucose (>2 hours post-prandial) >11.1 in plasma.

Glucose tolerance test is indicated when results are equivocal or to establish the diagnosis of gestational diabetes.

The Glucose challenge test is used to screen for gestational diabetes; see Antenatal screening.

Monitoring (control)

Glucose test strips, usually done by patient.

Glycated haemoglobin to assess control over the previous 3 months.

Fructosamine is rarely used, giving an indication of control over the previous 3 weeks.

For insulin-dependent diabetes, Urinalysis for ketones should also be performed.

Acutely ill diabetic, including

Glucose, Electrolytes, Anion bicarbonate gap, Urea, Creatinine.

Blood gas arterial, Hydroxybutyrate, Lactate, Full blood count if indicated.

Urine ketosis.

Osmolality can be calculated; direct measurement is not required.

The possibility of underlying infection should be considered, especially Urinary tract infection.



  • Ketoacidosis

Patients with ketoacidosis may not have severe hyperglycaemia.

If lactic acidosis is present, urine ketone tests may underestimate the degree of ketoacidosis.

Consider: Blood culture, Urea, Electrolytes, Creatinine, Glucose, Full blood count, Blood gas arterial (venous), Ward test urine. See Guideline on Pathology testing in the Emergency department: Appendix 2.

Frequent monitoring of Glucose and Electrolytes, especially Potassium, is required.

  • Hyperosmolar non-ketotic coma




Long-term consequences


Diabetic nephropathy

Albumin urine ('microalbuminuria') for early detection of nephropathy. Albumin to Creatinine ratio.

Urine microscopy and Urinalysis.

Creatinine, Urea, eGFR.

Renal biopsy if considered appropriate.

See also Nephrotic syndrome, Renal failure - chronic.

Diabetic retinopathy



Peripheral neuropathy

Peripheral vascular disease



See Immunodeficiency - secondary and Infection (increased susceptibility).

  • Urinary tract infection


  • Candidiasis


Renal papillary necrosis


Pregnancy and neonatal complications


Difficult control

Management requirements change during pregnancy; monitoring may be required more frequently.

Fetal macrosomia

Birth of a disproportionately large baby is an indication for careful maternal assessment for diabetes during subsequent pregnancies and is associated with an increased risk of diabetes in later life.

Fetal abnormalities


Neural tube defects

Plasma Alpha-fetoprotein at 14-16 weeks gestation; amniotic fluid alpha fetoprotein if plasma level is increased and fetal abnormality has not been identified on ultrasound.

Spontaneous abortion

Fetal death

Respiratory distress syndrome


Neonatal hypoglycaemia

Observation and blood glucose monitoring of neonate.

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