Oral Glucose Lowering Agents (OGLAs)

Last updated: March 18, 2026

Table Of Contents

Drugs Used in Diabetes Mellitus
Metformin
GLP-1 agonists
DPP-4 inhibitors
Sulfonylureas
Thiazolidinediones

Drugs Used in Diabetes Mellitus

Class	Example
Biguanides	Metofrmin
SGLT-2 inhibitors	Canagliflozin, empagliflozin, dapagliflozin
GLP-1 agonists	Exenatide, liraglutide, semaglutide
DPP-4 inhibitors	Sitagliptin, linagliptin
Sulfonylureas	Glipizide, gliburide, chlorpropamide
Thiazolidinediones	Pioglitazone, rosiglitazone

Metformin

Metformin – a biguanide – is one of the cornerstones of pharmacotherapy for T2DM, along with exercise and diet. It has a number of actions that improve glucose tolerance. Unlike sulphonylureas, metformin does not cause hypoglycaemia or weight gain and is therefore preferred as the first-line treatment – particularly in overweight patients.

Mechanism of action
- Inhibits hepatic gluconeogenesis
- Increases insulin sensitivity
- Reduces gastrointestinal absorption of carbohydrates
Indications
- Type 2 diabetes
- Polycystic ovarian syndrome
- Non-alcoholic fatty liver disease
Contraindications
- Chronic kidney disease
  - Review dose if creatinine is > 130 umol/L (eGFR < 45 ml/min)
  - Stop if creatinine is > 150 umol/L (eGFR < 30 ml/min)
- Advanced cirrhosis
- Lung disease
- States of tissue hypoxia, e.g., myocardial infarction, sepsis, acute kidney injury, and severe dehydration
- Iodine-containing contrast media (angiography, pyelography) since these can provoke renal impairment due to contrast nephropathy
  - Stop metformin on the day of the procedure and continue 48 hours after
- Alcohol abuse (relative contraindication)
Adverse effects
- Lactic acidosis
- Gastrointestinal upset i.e., nausea, anorexia, diarrhoea (intolerable in 20% of patients)

GLP-1 agonists

GLP-1 agonists are commonly used as an adjunct to metformin or as an alternative. They are typically given as a subcutaneous injection and are very expensive. GLP-1 agonists have been approved for weight loss. They are therefore an attractive choice for diabetic patients who are obese. They have a few, but severe adverse effects.

Mechanism of action
- Mimics GLP-1 → increased insulin secretion and reduced glucagon secretion
Indications
- BMI > 35 with a specific psychological or medical condition associated with obesity
- BMI < 35 for whom insulin therapy would have significant occupational implications
Contraindications
- MEN-2 syndrome
- Personal history or family history of medullary thyroid cancer
Adverse effects
- Acute pancreatitis

DPP-4 inhibitors

DPP-4 inhibitors are commonly used as adjuncts to metformin or as alternatives. They have a similar mechanism to GLP-1 agonists but are weight-neutral. They have very few adverse effects.

Mechanism of action
- Inhibition of DPP-4 enzymes → reduced degradation of incretins (GLP-1 and GIP) → increased insulin synthesis and reduced glucagon release
Indications
- Monotherapy in patients intolerant to metformin
- Dual therapy with other drugs
- Combination with insulin
- Diabetes with chronic kidney disease
- Diabetic patients at risk of hypoglycaemia
- Elderly patients with diabetes
- Overweight or obese diabetic patients
Contraindications
- Hypersensitivity
- Diabetic ketoacidosis
- Pregnancy and breastfeeding

Sulfonylureas

Sulfonylureas have fallen out of favour (due to weight gain and hypoglycemia). They still may be an appropriate monotherapy for patients in whom metformin is contraindicated.

Mechanism of action
- Bind to ATP-dependent K+ channels → increased insulin release
Adverse effects
- Weight gain
- Hypoglycemia (especially with long-acting preparations)
- Rare side effects
  - SIADH
  - Bone marrow suppression
  - Cholestasis
  - Peripheral neuropathy
Contraindications
- Pregnancy
- Breastfeeding

Thiazolidinediones

Thiazolidinediones have fallen out of favour due to their propensity to cause water retention. They may still be an appropriate monotherapy for patients in whom metformin is contraindicated.

Mechanism of action
- Agonism at PPAR-gamma receptor → increase peripheral insulin sensitivity
- Weight-neutral
Contraindications
- Congestive heart failure
Adverse effects
- Liver disturbances (monitor LFTs)
- Water retention (edema)
- Weight gain
- Increased risk of fractures
- Increased risk of bladder cancer (hazard ratio of 2.64)

Reference Intervals ›

Biochemistry

ACTH	P: <80 ng/L
ALT	P: 5–35 U/L
Albumin	P: 35–50 g/L
Aldosterone	P: 100–500 pmol/L
Alk. phosphatase	P: 30–130 U/L
α-Amylase	P: 0–180 IU/dL
α-Fetoprotein	S: <10 kU/L
Angiotensin II	P: 5–35 pmol/L
ADH	P: 0.9–4.6 pmol/L
AST	P: 5–35 U/L
Bicarbonate	P: 24–30 mmol/L
Bilirubin	P: 3–17 μmol/L
BNP	P: <50 ng/L
CRP	P: <10 mg/L
Calcitonin	P: <0.1 mcg/L
Calcium (ionized)	P: 1.0–1.25 mmol/L
Calcium (total)	P: 2.12–2.60 mmol/L
Chloride	P: 95–105 mmol/L
Cholesterol	P: <5.0 mmol/L
VLDL	P: 0.128–0.645 mmol/L
LDL	P: <2.0 mmol/L
HDL	P: 0.9–1.93 mmol/L
Cortisol AM	P: 450–700 nmol/L
Cortisol Midnight	P: 80–280 nmol/L
CK ♂	P: 25–195 U/L
CK ♀	P: 25–170 U/L
Creatinine	P: 70–100 μmol/L
Ferritin	P: 12–200 mcg/L
Folate	S: 2.1 mcg/L
FSH	P: 2–8 U/L ♂; >25 menopause
GGT ♂	P: 11–51 U/L
GGT ♀	P: 7–33 U/L
Glucose (fasting)	P: 3.5–5.5 mmol/L
Growth hormone	P: <20 mu/L
HbA1C (DCCT)	B: 4–6%
HbA1C (IFCC)	B: 20–42 mmol/mol
Iron ♂	S: 14–31 μmol/L
Iron ♀	S: 11–30 μmol/L
Lactate (venous)	P: 0.6–2.4 mmol/L
Lactate (arterial)	P: 0.6–1.8 mmol/L
LDH	P: 70–250 U/L
LH	P: 3–16 U/L
Magnesium	P: 0.75–1.05 mmol/L
Osmolality	P: 278–305 mosmol/kg
PTH	P: 0.8–8.5 pmol/L
Potassium	P: 3.5–5.3 mmol/L
Prolactin ♂	P: <450 U/L
Prolactin ♀	P: <600 U/L
PSA	P: 0–4 mcg/mL
Protein (total)	P: 60–80 g/L
Red cell folate	B: 0.36–1.44 μmol/L
Renin (erect)	P: 2.8–4.5 pmol/mL/h
Renin (recumbent)	P: 1.1–2.7 pmol/mL/h
Sodium	P: 135–145 mmol/L
TBG	P: 7–17 mg/L
TSH	P: 0.5–4.2 mU/L
T4	P: 70–140 nmol/L
Free T4	P: 9–22 pmol/L
TIBC	S: 54–75 μmol/L
Triglycerides	P: 0.50–2.3 mmol/L
T3	P: 1.2–3.0 nmol/L
Troponin T	P: <0.1 mcg/L
Urate ♂	P: 210–480 μmol/L
Urate ♀	P: 150–390 μmol/L
Urea	P: 2.5–6.7 mmol/L
Vitamin B12	S: 0.13–0.68 nmol/L
Vitamin D	S: 50 nmol/L

Arterial Blood Gases

pH	7.35–7.45
PaCO₂	4.7–6.0 kPa
PaO₂	>10.6 kPa
Base excess	±2 mmol/L

Urine

Cortisol (free)	<280 nmol/24h
Hydroxyindole acetic acid	16–73 μmol/24h
Hydroxymethylmandelic acid	16–48 μmol/24h
Metanephrines	0.03–0.69 μmol/mmol cr.
Osmolality	350–1000 mosmol/kg
17-Oxogenic steroids ♂	28–30 μmol/24h
17-Oxogenic steroids ♀	21–66 μmol/24h
17-Oxosteroids ♂	17–76 μmol/24h
17-Oxosteroids ♀	14–59 μmol/24h
Phosphate (inorganic)	15–50 mmol/24h
Potassium	14–120 mmol/24h
Protein	<150 mg/24h
Protein/creatinine ratio	<3 mg/mmol
Sodium	100–250 mmol/24h

Haematology

WCC	4.0–11.0 ×10⁹/L
RBC ♂	4.5–6.5 ×10¹²/L
RBC ♀	3.9–5.6 ×10¹²/L
Hb ♂	130–180 g/L
Hb ♀	115–160 g/L
PCV ♂	0.4–0.54 L/L
PCV ♀	0.37–0.47 L/L
MCV	76–96 fL
MCH	27–32 pg
MCHC	300–360 g/L
RDW	11.6–14.6%
Neutrophils	2.0–7.5 ×10⁹/L (40–75%)
Lymphocytes	1.0–4.5 ×10⁹/L (20–45%)
Eosinophils	0.04–0.44 ×10⁹/L (1–6%)
Basophils	0–0.10 ×10⁹/L (0–1%)
Monocytes	0.2–0.8 ×10⁹/L (2–10%)
Platelets	150–400 ×10⁹/L
Reticulocytes	0.8–2.0% / 25–100 ×10⁹/L
Prothrombin time	10–14 s
APTT	35–45 s

Paediatric

Pulse Rate (bpm)
Neonate	140–160
Infant <1yr	120–140
1–5 years	110–130
5–12 years	80–120
>12 years	70–100
Respiratory Rate (tachypnoea)
0–2 months	≥60/min
2–12 months	≥50/min
1–5 years	≥40/min
>5 years	≥30/min
Blood Pressure (mmHg)
Term	65/45
1 year	75/50
4 years	85/60
8 years	95/65
10 years	100/70
Weight Formulas
3–12 months	(a + 9)/2 kg
1–6 years	2a + 8 kg
>6 years	(7a − 5)/2 kg
Haemoglobin (g/dL)
Term newborn	13–20
1 month	11–18
2 months	10–15
1–2 years	10–13
>2 years	11–14
MUAC (6 months–5 years)
Obese	>17.5 cm
Normal	13.5–17.4 cm
At risk	12.5–13.4 cm
Moderate malnutrition	11.5–12.4 cm
Severe malnutrition	<11.5 cm
Developmental Milestones
Social smile	1.5 months
Head control	4 months
Sits unsupported	7 months
Crawls	10 months
Stands unsupported	10–12 months
Walks	12–13 months
Talks	18 months
CSF WBC (/mm³)
Term newborn	0–25
>2 weeks	0–5

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