Damien O’Brien MPSI provides an overview of diabetes, including diagnosis, treatment options, and monitoring strategies
Introduction
Diabetes mellitus is a common chronic metabolic disorder characterised by persistent hyperglycaemia. In Ireland, it is estimated that over 300,000 people have diabetes, with its prevalence continuing to rise due to an ageing population, rising obesity rates and increasingly sedentary lifestyles.
Diabetes is associated with significant morbidity and mortality, contributing to cardiovascular disease, chronic kidney disease, visual impairment and lower limb complications. In recent years, advances in diabetes management have transformed patient care. Alongside established therapies, newer drug classes have improved glycaemic control while also demonstrating significant cardiovascular and renal benefits. Furthermore, developments in diabetes technology such as continuous glucose monitoring systems and insulin pump therapy have enabled more personalised and effective diabetes management.
Pharmacists, as some of the most accessible healthcare professionals, play an important role in supporting patients with diabetes through medicines optimisation, patient education, lifestyle counselling and early recognition of complications. This article provides an overview of diabetes, including its pathophysiology, diagnosis, lifestyle management, pharmacological treatment options, monitoring, and the expanding role of the pharmacist in delivering patient-centred care.
Background on Diabetes
Diabetes is a group of chronic metabolic disorders characterised by elevated blood glucose levels resulting from impaired insulin secretion, impaired insulin action, or both. Persistent hyperglycaemia is associated with progressive damage to multiple organ systems. Macrovascular complications affect the large blood vessels and include coronary artery disease, peripheral arterial disease and cerebrovascular disease, increasing the risk of myocardial infarction, stroke and lower limb amputation. Microvascular complications affect the small blood vessels and typically include retinopathy, nephropathy and neuropathy.
The two most common types of diabetes are type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM). T1DM is an autoimmune condition characterised by the immune-mediated destruction of pancreatic beta cells, resulting in insulin deficiency. It commonly presents in childhood or early adulthood, although it can occur at any age. A combination of genetic predisposition and environmental factors may trigger autoimmunity.
T2DM is characterised primarily by insulin resistance, whereby peripheral tissues become less responsive to insulin. Progressive pancreatic beta cell dysfunction leads to inadequate insulin production, resulting in persistent hyperglycaemia. T2DM accounts for approximately 90-to-95 per cent of all diabetes cases. It typically presents in adults over 45 years of age, but it is increasingly observed in younger populations due to rising obesity rates and physical inactivity.
The development of T2DM involves a complex interplay between genetic susceptibility and lifestyle factors, including poor diet, obesity and a lack of physical activity. T2DM often has a gradual onset, with many patients remaining asymptomatic for years.
Symptoms of T1DM include polyuria, polydipsia, polyphagia, fatigue, unexplained weight loss, and blurred vision. These symptoms typically develop rapidly and, if left untreated, may progress to diabetic ketoacidosis (DKA), a life-threatening medical emergency.
The symptoms of T2DM are often similar and may also include recurrent infections and slow-healing wounds. However, many patients with T2DM remain asymptomatic for several years, highlighting the importance of screening high-risk patients and establishing an early diagnosis to reduce the risk of long-term complications.
Gestational diabetes mellitus (GDM) develops during pregnancy and is associated with an increased risk of maternal and foetal complications, as well as an increased lifetime risk of developing T2DM. Less common forms of diabetes include maturity-onset diabetes of the young (MODY) and diabetes secondary to pancreatic disease or certain medications.
Diagnosis
Early diagnosis and initiation of treatment are essential to reduce the risk of diabetes-related complications. The diagnosis of diabetes is based on characteristic symptoms and confirmed using plasma glucose measurements or glycated haemoglobin (HbA1c). A diagnosis of diabetes can be made if any of the following criteria are met:
? Fasting plasma glucose level ?7.0 mmol/L following fasting for at least eight hours.
? Oral glucose tolerance test (OGTT): A plasma glucose level ?11.1 mmol/L two hours after a 75g oral glucose load.
? Glycated haemoglobin (HbA1c) level ? 48 mmol/mol (6.5%): HbA1c reflects the average plasma glucose concentration over the preceding two-to-three months and is used in both the diagnosis and monitoring of diabetes.
? Random plasma glucose level ?11.1mmol/L along with symptoms of hyperglycaemia.
Early diagnosis and initiation of treatment are essential to reduce the risk of diabetes-related complications
Treatment
Following diagnosis, management of diabetes should be individualised for each patient. Treatment is often complex and requires several interventions, with both lifestyle management and pharmacological treatment often required for successful long-term disease management. Patient education and engagement are vital for effective disease management. Lifelong treatment is often necessary to reduce diabetes-related complications.
HbA1c is the cornerstone for assessing long-term glycaemic control, with a target of <53mmol/mol often appropriate for many patients, although less stringent targets may be suitable in some cases. However, aggressive management may increase the risk of hypoglycaemia. In addition to glycaemic control, optimisation of blood pressure, lipid levels and other cardiovascular risk factors forms an integral part of diabetes management.
Non-Pharmacological Treatment
Lifestyle modification is the cornerstone of diabetes management for all patients. Although pharmacological treatment is essential in T1DM, lifestyle interventions also play an important role in optimising glycaemic control, reducing cardiovascular risk and improving overall health outcomes. In T2DM, lifestyle changes may delay disease progression, improve insulin sensitivity and achieve diabetes remission in some cases.
An individualised nutritional plan reflecting the patient’s preferences, lifestyle and treatment goals is recommended. Patients should be encouraged to consume a balanced diet rich in vegetables, fruit, wholegrains, legumes and lean protein sources, while limiting refined carbohydrates, saturated fats and foods high in free sugars.
Patients with T1DM may benefit from consultation with a dietitian to support carbohydrate estimation and to optimise mealtime insulin dosing. Regular physical activity is also an important consideration, with adults encouraged to undertake at least 150 minutes of moderate-intensity aerobic exercise each week. In overweight or obese patients with T2DM, sustained weight loss can improve insulin sensitivity, glycaemic control and overall cardiovascular health. Smoking cessation should be strongly encouraged in both T1DM and T2DM, as smoking further increases cardiovascular risk. Alcohol intake should be moderated, with patients advised that alcohol may increase the risk of hypoglycaemia.
Pharmacological Treatment
Pharmacological management is essential in T1DM and is often required in T2DM when lifestyle interventions alone are insufficient to achieve glycaemic targets. Treatment should be individualised, with medication choices guided by glycaemic control, comorbidities, cardiovascular risk, renal risk, body weight, risk of hypoglycaemia and patient preferences.
Type 1 Diabetes Mellitus
Lifelong insulin replacement therapy is required for T1DM. The objective of treatment is to mimic physiological insulin secretion through the administration of basal and prandial insulin. This can be achieved using either a multiple daily injection regimen (basal-bolus therapy) or continuous subcutaneous insulin infusion.
A multiple daily injection regimen typically involves administering a long-acting basal insulin once or twice daily, with a rapid-acting insulin before meals. Insulin doses should be individually titrated to achieve optimal glycaemic control while minimising the risk of both hypoglycaemia and hyperglycaemia.
Long-acting basal insulin analogues, including insulin glargine, insulin degludec and insulin detemir, provide background insulin coverage throughout the day. Rapid-acting insulin analogues, such as insulin lispro, insulin aspart and insulin glulisine, are administered before meals to control postprandial glucose levels.
Continuous subcutaneous insulin infusion, commonly referred to as insulin pump therapy, is increasingly used in the management of T1DM. This delivers a continuous infusion of rapid-acting insulin to provide basal insulin requirements, with patient-activated bolus doses administered before meals for prandial coverage. This therapy offers greater flexibility and may improve glycaemic control in appropriate patients.
Continuous subcutaneous insulin infusion, commonly referred to as insulin pump therapy, is increasingly used in the management of T1DM
Type 2 Diabetes Mellitus
Pharmacological management of T2DM is often progressive and highly individualised. Pharmacological management is indicated if glycaemic targets cannot be achieved through diet and exercise. The objective of treatment is to achieve optimal glycaemic control, to reduce the risk of cardiovascular and renal complications, and improve quality of life.
Metformin is considered first-line treatment for many patients with T2DM. It is a biguanide that lowers blood glucose by decreasing hepatic glucose production, reducing intestinal glucose absorption, and improving insulin sensitivity. Metformin may be used as monotherapy or in combination with other glucose-lowering therapies. It has the benefits of a low risk of hypoglycaemia and having a well-established safety profile. Common adverse effects include nausea, vomiting, diarrhoea and abdominal pain, which may be minimised through gradual dose titration, administration with food or the use of modified-release formulations.
Sulfonylureas are an effective glucose-lowering treatment option in T2DM, with gliclazide an example. They stimulate pancreatic beta cells to increase insulin secretion. They can be used as monotherapy or in combination with other antidiabetic drugs, except the meglitinides, as they have a similar mechanism of action. Treatment should be initiated at a low dose and titrated according to glycaemic response. Sulfonylureas are associated with weight gain and an increased risk of hypoglycaemia, particularly in older adults, after missing meals or with high doses. Although they continue to have an important role in selected patients, their use has declined with the availability of newer therapies that offer additional cardiovascular and renal benefits with a lower risk of hypoglycaemia.
Dipeptidyl peptidase-4 (DPP-4) inhibitors, including sitagliptin, linagliptin and saxagliptin, provide another treatment option for T2DM. They inhibit degradation of endogenous incretin hormones, increasing glucose-dependent insulin secretion while reducing glucagon secretion. They can be used as monotherapy or as an add-on treatment option with other antidiabetic medications. They are typically well-tolerated with a low risk of hypoglycaemia.
Sodium-glucose co-transporter-2 (SGLT2) inhibitors work by inhibiting glucose reabsorption in the proximal renal tubules, thereby promoting urinary glucose excretion. Dapagliflozin, empagliflozin and canagliflozin are commonly prescribed examples. In addition to lowering blood glucose levels, SGLT2 inhibitors have demonstrated significant cardiovascular and renal benefits, making them particularly beneficial in patients with heart failure or chronic kidney disease. They may also promote modest weight loss and have a relatively low risk of hypoglycaemia.
Patients should be counselled on the importance of maintaining adequate hydration and the need to temporarily withhold treatment during acute illness in accordance with sick day rules, due to the rare risk of diabetic ketoacidosis. The most common adverse effects include genital mycotic infections, increased urination and volume depletion, while urinary tract infections may also occur.
Glucagon-like peptide-1 (GLP-1) receptor agonists activate the GLP-1 receptor, which enhances glucose-dependent insulin secretion, suppresses glucagon release and delays gastric emptying. Dulaglutide, semaglutide and liraglutide are examples of GLP-1 receptor agonists used to treat T2DM. They can be used as monotherapy or in combination with other glucose-lowering therapies. In addition to improving glycaemic control, these agents promote significant weight loss and have demonstrated cardiovascular and renal benefits, making them particularly valuable in patients with obesity or established cardiovascular disease.
Most GLP-1 receptor agonists are administered by subcutaneous injection. An oral formulation of semaglutide is available in other countries, although not yet in Ireland. Gastrointestinal adverse effects, including nausea, vomiting and diarrhoea, are the most common and may be minimised through gradual dose escalation, while there is a relatively low risk of hypoglycaemia. Their use has increased substantially in recent years and pharmacists have an important role in counselling patients on administration, dose titration, adherence, and management of adverse effects.
Thiazolidinediones, such as pioglitazone, may be appropriate for selected patients but are not considered first-line treatment because of their adverse effect profile. They work by acting on intracellular metabolic pathways to improve insulin action and increase insulin sensitivity. Potential adverse effects include weight gain, fluid retention, increased risk of fractures, worsening heart failure, and possible increased risk of bladder cancer with prolonged use. However, they may be useful in selected cases as they are not contraindicated in patients with renal disease.
Meglitinides work by binding to receptors on beta cells in the pancreas, stimulating insulin secretion. Repaglinide is an example of an agent in this class. The most clinically significant adverse effects are hypoglycaemia and weight gain. However, they are now rarely used in clinical practice following the introduction of newer glucose-lowering therapies.
As T2DM progresses, many patients will require insulin therapy due to declining pancreatic beta cell function. Insulin may also be required temporarily during acute illness, surgery, or at the time of diagnosis in patients presenting with marked hyperglycaemia. Insulin remains the most effective glucose-lowering therapy but is associated with an increased risk of hypoglycaemia and weight gain. Pharmacists play a role in supporting patients on insulin therapy by providing education on injection technique, storage requirements, dosing, blood glucose monitoring and management of hypoglycaemia.
The expanding range of pharmacological treatment now allows treatment to be tailored to the individual patient. Modern diabetes management extends beyond glycaemic control, with increasing emphasis on reducing cardiovascular and renal complications while improving quality of life through a personalised, patient-centered approach.
Monitoring
Effective diabetes management requires regular monitoring to assess treatment efficacy, identify complications and support timely intervention when required. Routine assessment should include measurement of HbA1c, blood pressure, lipid profile and renal function. Patients should also be encouraged to undergo regular diabetic retinal screening and foot assessments to enable the early detection and management of complications. Patients should be counselled on the importance of recognising and managing hypoglycaemia. Furthermore, they should be up to date with recommended vaccinations, including influenza, Covid-19 and pneumococcal vaccines where appropriate, due to their increased susceptibility to infection and associated complications. Community pharmacists are ideally placed to reinforce these measures.
Self-monitoring of blood glucose levels is an important component of diabetes care, particularly for patients receiving insulin therapy. Blood glucose testing helps patients understand the effects of diet, exercise and medication on glycaemic control, while also allowing for the recognition and management of hypoglycaemia and hyperglycaemia.
Recent advances in diabetes technology have transformed patient care. Continuous glucose monitoring systems measure glucose levels throughout the day and provide real-time glucose readings and alerts for both hypoglycaemia and hyperglycaemia. These technologies improve glycaemic control when compared with traditional testing. Many continuous glucose monitoring systems are now integrated with insulin pumps to create systems that can automatically adjust insulin delivery in response to glucose readings, representing a significant advancement in the management of T1DM.
The Role of the Pharmacist
Pharmacists have an important role in the management of diabetes beyond the traditional dispensing of medication. Pharmacists are one of the most accessible healthcare professionals and are frequently in contact with patients, allowing them to support patients at various points of their journey.
Medication adherence is often an issue in T2DM due to its asymptomatic nature and adverse effects of certain medications. Pharmacists can address this challenge through thorough patient counselling, medicines optimisation and regular medication reviews. They also play an important role in educating patients about the safe and effective use of diabetes therapies, including demonstrating injection technique, advising on storage of medication, reinforcing sick day rules and counselling on the use of continuous glucose monitoring systems and insulin pumps. In addition to pharmacological management, pharmacists can support lifestyle interventions through smoking cessation services, weight management advice, and the promotion of physical activity.
Optimal diabetes management requires a collaborative multidisciplinary approach involving many healthcare specialists. Pharmacists, through accessible and patient-centred care, can make a significant contribution to improving health outcomes for patients with diabetes.
References available upon request
