Many people starting GLP-1 receptor agonist therapy for type 2 diabetes or weight management wonder whether these medications will affect their energy levels. Whilst GLP-1 receptor agonists are not stimulants and do not directly increase energy production, some patients report feeling more energetic during treatment. This improvement is typically linked to better blood glucose control, weight loss, and overall metabolic health rather than a direct pharmacological effect on energy. Understanding how these medications work and what to realistically expect can help you make informed decisions about your treatment.

What Are GLP-1 Receptor Agonists and How Do They Work?

GLP-1 receptor agonists are a class of medications that mimic the action of glucagon-like peptide-1, a naturally occurring hormone produced in the intestine. These medicines are primarily prescribed for the management of type 2 diabetes and, in specific formulations, for weight management in adults with obesity or overweight with weight-related comorbidities.

In the UK, commonly prescribed GLP-1 receptor agonists include:

• Semaglutide (Ozempic for type 2 diabetes; Wegovy for weight management)

• Dulaglutide (Trulicity for type 2 diabetes only)

• Liraglutide (Victoza for type 2 diabetes; Saxenda for weight management)

The mechanism of action centres on several key physiological effects. GLP-1 receptor agonists work by:

• Enhancing insulin secretion from pancreatic beta cells in a glucose-dependent manner, which helps lower blood glucose levels without causing excessive hypoglycaemia

• Suppressing glucagon release from alpha cells, reducing hepatic glucose production

• Slowing gastric emptying, which prolongs the feeling of fullness after meals

• Acting on appetite centres in the brain, particularly the hypothalamus, to reduce hunger and food intake

These medications are administered via subcutaneous injection, typically once weekly or once daily depending on the specific formulation. The MHRA has approved various GLP-1 receptor agonists for use in the UK, and NICE provides guidance on their appropriate prescribing within NHS pathways. Weight management formulations (Wegovy, Saxenda) are typically initiated by specialist weight management services (tier 3 or 4) according to NICE criteria.

GLP-1 receptor agonists are not classified as stimulants and do not directly increase energy expenditure in a clinically meaningful way. Their effects on glucose regulation, weight, and overall metabolic health may indirectly influence how patients perceive their energy levels. These medications are not indicated for type 1 diabetes or diabetic ketoacidosis.

Why Some People Feel More Energetic on GLP-1 Treatment

Many patients report feeling more energetic after starting GLP-1 therapy, though there is no official direct link between these medications and increased energy production at a cellular level. Instead, the perceived improvement in energy is likely multifactorial and related to the broader metabolic improvements these medications facilitate.

Improved glycaemic control is perhaps the most significant contributor. People with poorly controlled type 2 diabetes often experience fatigue due to fluctuating blood glucose levels. Hyperglycaemia can cause symptoms including tiredness, lethargy, and difficulty concentrating. By stabilising blood glucose within target ranges, GLP-1 receptor agonists may alleviate these symptoms, leading to a subjective sense of having more energy throughout the day.

Weight loss associated with GLP-1 therapy can also contribute to improved energy levels. Carrying excess weight places additional strain on the cardiovascular system and musculoskeletal structures, and obesity is associated with increased fatigue. The degree of weight loss varies by medication and dose; semaglutide 2.4 mg (Wegovy) has demonstrated weight loss of 10-15% in clinical trials, while other GLP-1 medications and lower doses typically produce more modest results. As patients lose weight, they often report:

• Improved mobility and reduced joint discomfort

• Better sleep quality and reduced sleep apnoea symptoms

• Improved exercise tolerance

• Improved mood and psychological wellbeing

Some patients may experience reduced inflammatory markers (such as C-reactive protein) as metabolic health improves. Chronic low-grade inflammation associated with obesity and insulin resistance may contribute to fatigue, though the direct relationship between reduced inflammation and energy levels requires further research.

It is important to note that these energy improvements typically develop gradually over weeks to months as metabolic changes take effect, rather than immediately upon starting treatment. Persistent or worsening fatigue despite treatment warrants medical review to investigate other potential causes such as anaemia, thyroid disorders, sleep apnoea, depression, or medication side effects.

Potential Side Effects That May Affect Your Energy

Whilst some patients report increased energy on GLP-1 therapy, others may experience side effects that temporarily reduce energy levels, particularly during the initial treatment phase. Understanding these potential adverse effects is essential for setting realistic expectations.

Gastrointestinal side effects are the most commonly reported adverse reactions with GLP-1 receptor agonists. These include:

• Nausea (affecting 20-40% of patients initially)

• Vomiting

• Diarrhoea

• Constipation

• Abdominal discomfort

These symptoms can be debilitating during the first few weeks of treatment and may cause fatigue, reduced appetite, and general malaise. The gastrointestinal effects typically diminish as the body adjusts to the medication, usually within 4-8 weeks. Starting with a lower dose and gradually titrating upwards, as recommended in prescribing guidelines, helps minimise these effects.

Reduced caloric intake resulting from appetite suppression may initially cause feelings of low energy, particularly if patients are not consuming adequate nutrition. It is important to maintain a balanced diet with sufficient protein, vitamins, and minerals even when appetite is reduced. Some patients may benefit from consultation with a dietitian to ensure nutritional adequacy.

Hypoglycaemia is uncommon with GLP-1 receptor agonists alone due to their glucose-dependent mechanism, but the risk increases when used in combination with insulin or sulfonylureas. Low blood glucose can cause symptoms including fatigue, weakness, dizziness, confusion, tremor, sweating, and irritability.

Other important side effects that may affect wellbeing include:

• Gallbladder problems (pain in the right upper abdomen, fever, jaundice)

• Dehydration leading to acute kidney injury, especially if vomiting or diarrhoea is severe

• Worsening of diabetic retinopathy in some patients, particularly with semaglutide

• Allergic reactions (rash, swelling, breathing difficulties)

Patients should report suspected side effects to their healthcare provider and can also report them through the MHRA Yellow Card scheme. Those experiencing recurrent hypoglycaemia, severe gastrointestinal symptoms, or concerning new symptoms should contact their GP or diabetes specialist team promptly.

What to Expect When Starting GLP-1 Therapy in the UK

If you are considering or have been prescribed a GLP-1 receptor agonist through the NHS or private healthcare in the UK, understanding what to expect can help you navigate the treatment journey more effectively.

Initial assessment and prescribing: GLP-1 receptor agonists for type 2 diabetes are typically prescribed by GPs, practice nurses with prescribing rights, or specialist diabetes teams according to NICE guidance. For weight management, medications like Wegovy (semaglutide 2.4 mg) and Saxenda (liraglutide 3 mg) are usually initiated by specialist weight management services (tier 3 or 4) with specific eligibility criteria and treatment duration limits (typically up to 2 years).

Dose titration and monitoring: Treatment usually begins with a low starter dose, which is gradually increased over several weeks to months. This stepwise approach minimises side effects. For example:

• Ozempic (for diabetes) typically starts at 0.25 mg weekly, increasing to 0.5 mg, then potentially to 1 mg (with a 2 mg option in some cases)

• Wegovy (for weight management) follows a different titration schedule up to 2.4 mg weekly

Regular follow-up appointments will monitor:

• Blood glucose levels (HbA1c testing every 3-6 months)

• Weight changes

• Blood pressure

• Renal function

• Side effects and tolerability

• Injection technique

• Retinal screening (particularly important for people with diabetes on semaglutide)

Timeline for effects: Regarding energy levels specifically, patients should understand that any improvements are likely to be gradual rather than immediate. Glycaemic control typically improves within the first few weeks, whilst significant weight loss and associated energy improvements may take 3-6 months to become apparent.

When to contact your healthcare provider: You should seek medical advice if you experience:

• Severe or persistent nausea and vomiting preventing adequate fluid intake

• Signs of pancreatitis (severe abdominal pain radiating to the back)

• Gallbladder symptoms (pain in the right upper abdomen, fever, jaundice)

• Symptoms of hypoglycaemia if taking other diabetes medications

• Visual changes or worsening eyesight

• Severe allergic reactions (rash, swelling, breathing difficulties)

• Unexplained fatigue that worsens rather than improves

These medications are not recommended during pregnancy or breastfeeding. Women of childbearing potential should use effective contraception and stop treatment before planned pregnancy.

Your healthcare team can adjust your treatment plan, provide supportive management for side effects, or consider alternative therapies if GLP-1 receptor agonists are not suitable for you. Realistic expectations and open communication with your healthcare providers are key to successful treatment outcomes.

Frequently Asked Questions