Diabetes Medications

Article Last Updated:02/01/2026

Pharmacology and Prescription Information

Drug class	MoA	Examples	Overall clinical profile	Important side effects	Caution and contraindications
Biguanides	Metformin	Enhances the effect of insulin by: ↑ Peripheral insulin sensitivity (increases glucose uptake into cells) ↓ Hepatic gluconeogenesis	Promotes weight loss No risk of hypoglycaemia	GI upset – most common Metallic taste in the mouth Vitamin B12 deficiency Lactic acidosis (rare but serious)	Avoid if eGFR <30 Acute metabolic acidosis (including lactic acidosis and DKA) Stop in states of hypoxia (due to risk of lactacidosis) Shock Sepsis Respiratory failure
SGLT-2 inhibitor	Dapagliflozin, empagliflozin	Inhibit SLGT-2 in proximal renal tubule → ↓ glucose reabsorption	Promotes weight loss Cardioprotective effect	DKA (euglycaemic DKA possible) Risk of hypoglycaemia From the effects of glycosuria UTIs and genital infections Dehydration Fournier’s gangrene (necrotising fasciitis of the genitalia / perineum) It is normal to see glycosuria (typically ++ / +++ on urine dipstick) in those who take SGLT-2 inhibitors	T1DM Previous DKA (use with caution) Recurrent UTI (use with caution) Avoid if eGFR <15 Reduced efficacy if eGFR <45
Thiazolidinediones (TZD)	Pioglitazone	Activation of PPARγ in adipocytes → ↑ insulin sensitivity (increases glucose uptake into cells)	No warnings in renal impairment	ELBOW: E: oedema (↑ risk of heart failure) L: liver toxicity B: bladder cancer O: osteoporosis W: weight gain	Heart failure Previous / active bladder cancer Uninvestigated macroscopic haematuria
Sulfonylurea	Glicazide, glimepiride	↑ Insulin secretion	Useful to rapidly lower blood glucose	Risk of hypoglycaemia Weight gain	Presence of ketoacidosis G6PD deficiency (use with caution)
DPP-4 inhibitor	Sitagliptin, linagliptin	Inhibits DPP-4 (enzyme that breaks down GLP-1) → ↑ GLP-1 activity	Weight neutral Good tolerability No risk of hypoglycaemia Can be used in renal impairment	Headache – common Acute pancreatitis Constipation	History of pancreatitis (use with caution) Dose reduction if eGFR <45 (apart from linagliptin)
GLP-1 agonist	Liraglutide, exenatide, semaglutide	3 main effects of GLP-1: Delayed gastric emptying ↑ Insulin secretion ↓ Glucagon secretion	Has multiple additional benefits: Weight loss Cardioprotective Renoprotective Note that it is given via an injection	Effect of delayed gastric emptying Gastroparesis-like symptoms Risk of pulmonary aspiration during GA / deep sedation DKA (when used in combination with insulin, esp. after insulin discontinuation or rapid dose reduction) Acute pancreatitis Gall bladder disorder Risk of medullary thyroid carcinoma	Diabetic gastroparesis Chronic pancreatitis Personal / family history of medullary thyroid carcinoma or MEN2 syndrome

Acarbose is another anti-diabetic drug, but rarely used:

It has a poorer anti-hyperglycaemic effect than many other antidiabetic drugs
MoA: Reduce GI glucose absorption
AEs: bloating, flatulence, diarrhoea

High-Yield Facts

Metformin Dosing

Starting dose: 500mg daily
Maximum dose: 2g daily (usually 1g BD)
Timing to take metformin
- OD → take with breakfast
- BD → take with breakfast and dinner
- TDS → take with breakfast, lunch and evening meal

Drugs at Risk of Hypoglycaemia

2 main drugs:

Insulin
Sulfonylurea

SGLT-2 inhibitors carry a smaller risk of hypoglycaemia, but can occur if used in combination with insulin / sulfonylurea

Drugs at Risk of Weight Gain

Drugs that can cause weight gain:

Insulin
Sulfonylurea
TZD (pioglitazone)

Effect on weight for other drugs:

Weight neutral: metformin, DPP-4 inhibitor
Weight loss: GLP-1 agonist, SGLT-2 inhibitor

Drugs in Renal Impairment

The following drugs can be safely used in renal impairment:

TZD (pioglitazone)
Linagliptin (NB other DPP-4 inhibitors require dose-reduction)

Summary of other drugs in renal impairment:

Drug	Use in renal impairment
Metformin	Avoid if eGFR <30
SGLT-2 inhibitor	Avoid if eGFR <15 NB reduced efficacy if eGFR <45
Sulfonylurea	Dose reduction in renal impairment Avoid in severe renal impairment (due to risk of hypoglycaemia)
DPP-4 inhibitor (apart from linagliptin)	Dose reduction if eGFR <45
GLP-1 agonist	Avoid in renal impairment (exact cut-offs depend on the drug)

Drugs to avoid in T1DM

The only drugs that should be used in T1DM are:

Insulin – all patients
Metformin – if BMI >25 kg/m²

ALL other drugs should NOT be used in T1DM. See this article on management of T1DM.

Drugs and Pregnancy

The only drugs that are safe in pregnancy are:

Insulin
Metformin

All other drugs should be stopped. See this article on management of diabetes in pregnancy

Drugs to Avoid in Pancreatitis

DPP4 inhibitors and GLP-1 agonists should NOT be used in patients with a history of pancreatitis, or should be stopped immediately if a patient on them develops acute pancreatitis

References

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