Diabetes Mellitus- Notes for PLAB 1

Need to quickly review Diabetes – Diagnosis, Medication mnemonics, Pre-op management of diabetes and more? Have a quick read below:


  • Blood glucose <4mmol/L or <72mg/dL
  • Important Cause- Alcohol

Dx- Whipple’s Triad

  1. Low plasma glucose (usually <4)
  2. Manifestations (sweating, confusion, tachycardia, hypotension, altered mentation)
  3. If blood glucose is corrected- rapid resolution of symptoms occur


Conscious/ Drowsy

  • 200mL Fruit Juice
  • Oral Glucose Gel

Unconscious/Cannot Swallow

  • IV Glucose / 1mg Glucagon IM/SC (2 Tubes)


  • Glucagon


  • IV Glucose

Unconscious + Alcohol

  • Set IV line then IV Glucose (cannot use Oral and Glucagon)

Preparations of IV Glucose


  • 10 minutes- 150mL
  • 15 minutes- 200mL
  • Every 1-2 minutes- 50mL until patient conscious or 250mL given (5 times)


  • 10 minutes- 75mL
  • 15 minutes- 100mL


  • Diagnosis by C-peptide Test

Hyperosmolar Hyperglycaemic State

  • High Glucose + High Serum Osmolality but Without DKA


  • IVF 0.9% NS and Electrolyte Correction

Diabetic Ketoacidosis

  • Glucose >11 + Abdominal pain + Vomiting + Kussmaul breathing + Dehydration


  • Glucose>11 + Ketonuria ++/Ketonemia + ABG- pH < 7.3 + HCO3<15


0.9% NaCl initially > Insulin pump at 0.1unit/kg/hour > ABG or VBG> KCL 40mmol/L > D5/D10 when Glucose<12 > Don't use HCO3 (cerebral oedema)
  • 1 ltr IV fluid 0.9% over 1 hour (if systolic BP >90)


  • 1 ltr IV fluid 0.9% over 10-15 minutes (if systolic BP <90)

DKA or Sepsis

  • Baby with Severe dehydration (dry mucous membranes, sunken eyes and fontanelles, reduced skin turgor) + Hyponatremia + Hypokalemia


  • IV Fluids (0.9% NaCl + KCl)

Diabetes Mellitus


  • 1 Abnormal Value + Symptoms


  • 2 Abnormal values Without Symptoms

Abnormal values (FBG and not RBS, Preferred over HbA1c because cheaper)

  • FBS >_ 7 mmol/L (126 mg/dL)
  • HbA1c >_ 48 mmol/L (>6.5%) (Normal- 42, Target in DM= <48)

Pre-Diabetes (Impaired Glucose Tolerance)

Fasting- 5.5-6.9
2 hour Post-Prandial/ OGTT- 7.8-11 (140-200)
HbA1c- 42-47
  • Tiredness is not a symptom of DM alone
  • In Asymptomatic People with 1 abnormal value> repeat test in 2 weeks to confirm the diagnosis

Gestational DM/ Acromegaly

  • OGTT is DxOC


MODY (Maturity Onset Diabetes of Young)

  • DM <25 Y/O + FHx (2 generations) + Mild Hyperglycaemia
  • Rx- Refer to Endocrinology for Genetic Counselling + Lifestyle modifications
  • Sulphonylureas before Insulin
  • Rx- Refer to Endocrinologist

LADA- Late Autoimmune Diabetes of Adults (30-50 YO)

  • DM1 Variant with Slow Progression + Autoimmune Disease

DM1 vs DM2

  • GAD Antibodies (Glutamic Acid Decarboxylase)

Diabetes Treatment

  • Target- <_ 48 (<6.5)
  • Newly Diagnosed
  • First- Lifestyle Modifications
  • Still HbA1c>48? – Start 1 OHA (usually metformin)
  • Still High HbA1c?
  • <58- Lifestyle modifications

Diabetes Medications

  • Impaired KFT- Insulin/ Gliptins (DDP4)
  • C/I- With Bad Kidneys, avoid MS (Metformin, Sulfonylurea)
  • Biguanides- Metformin (<30 eGFR, reduce dose if <45)
  • Sulphonylureas (risk of Hypoglycaemia)


  • Increase (SPR)- Sulphonylureas (e.g., Glibenclamide), Glitazones (Pioglitazone), Repaglinide
  • Decreases- Biguanides (Metformin)
  • No effect- DDP4 (Gliptins)


  • Good- Insulin, Gliptins (DDP4)
  • Bad- Metformin, Sulphonylureas (With Bad Kidneys, avoid MS (Metformin, Sulfonylurea)
  • SGLT-2 inhibitors (Gliflozin)- contraindicated if GFR<60

Heart failure

  • Gliptins (DDP 4 inhibitors- also in Pancreatitis) and Glitazones (also in Bladder Cancer)
  • Preferred- SGLT2 Inhibitors (Dapagliflozin)
  • SGLT-2 inhibitors- contraindicated if GFR<60


  • With bad kidneys (GFR <30), do not use MS (Metformin, Sulphonylureas)
  • The heart has 4 chambers, so with Heart Failure (and Pancreatitis), do not use DDP4 inhibitors (Gliptins)
  • The Pie (Pioglitazone) comes with the die (Risk of bladder cancer). Pioglitazone is also contraindicated in Heart Failure
  • Hypoglycaemic that cause weight gain are SPR- Sulphonylureas, Pioglitazone, Repaglinide
  • The rest cause weight loss except DDP4 inhibitors (Gliptins) which have no effect on the weight
  • SPR without the P (SR) have the risk of hypoglycaemia: Sulphonylureas and Repaglinide

Euglycemic DKA

  • Occurs in SGLT-2 (Gliflozin)- All features of DKA but Blood Glucose is not elevated (<11), Ix- Capillary Ketones>Urinary Ketones, ABG, Rx- IV Fluids

Autonomic Neuropathy

  • Both Sympathetic and Parasympathetic branches (ANS)
  • Causes- Diabetes, Alcohol, Aging
  • Features- Sweating, Incontinence, Diarrhoea or Constipation, Impotence, Postural hypotension
  • Suspect it in DM patients with Persistent Diarrhoea
  • Metformin (Biguanide) can cause Diarrhoea as well
  • Stop DAMN drugs in any patients with Diarrhoea or Vomiting

Pre-Op Mx for Diabetes

T2DM (on OHAs)

  • Minor Surgery- Continue
  • Major Surgery (1 meal skip)- Continue
  • Longer Surgery (>1 meal skip)/ Uncontrolled DM- Switch to Insulin
  • Emergency Surgery- R/O DKA
  • Omit- Sulphonylureas (cause hypoglycaemia)
  • Longer surgery- Consider omitting Metformin
  • Safe to Use- Rest all

T1DM (on Insulin)

  • Minor Surgery- Omit Dose (morning if AM surgery, lunchtime if PM surgery)
  • Major- Switch to VRIII (Variable Rate Intravenous Insulin Infusion Ratio)
  • Before Sx- 80% of total once daily in VRIII (long-acting) + Continue Other Insulin
  • Intra-op- 80% of total once daily in VRIII (long-acting) + Stop Other Insulin
  • Target during Sx- 6-10 (max 12)
  • KCl + Glucose + NaCl also given
  • Emergency- Switch to VRIII
  • For Major Sx- In all cases, restart the previous regimen when per mouth diet is re-established + Check Blood glucose 4 hourly

Read our other guides for PLAB 1

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