Are you aware that GLP-1 treatments used for weight control and metabolism can make you feel cold? As intriguing as it sounds, this question is not uncommon among users of this revolutionary weight management solution. Here at Bolt Pharmacy, we aim to answer queries like this and debunk myths circling GLP-1 medications. Our hope? That our insights help anyone contemplating enduring and effective weight loss options, just like GLP-1. It's time to wrap up warm and dive into the icy waters of understanding weight loss injections.

How Weight Loss Injections Work in the Body

Weight loss injections, primarily glucagon-like peptide-1 (GLP-1) receptor agonists such as semaglutide (Wegovy) and liraglutide (Saxenda), work through several interconnected mechanisms to promote weight reduction. These medications are licensed by the MHRA for weight management in adults with obesity or those who are overweight with weight-related health conditions.

The primary mechanism involves mimicking the action of naturally occurring GLP-1, a hormone released by the intestine after eating. These injections bind to GLP-1 receptors in the brain, particularly in areas that regulate appetite and food intake. This action significantly reduces hunger and increases feelings of fullness (satiety), leading to reduced calorie consumption. Patients typically report feeling satisfied with smaller portion sizes and experiencing fewer food cravings between meals.

Additionally, GLP-1 receptor agonists slow gastric emptying, meaning food moves more gradually from the stomach into the small intestine. This prolonged digestion contributes to sustained feelings of fullness and helps stabilise blood glucose levels. The medications also influence insulin secretion from the pancreas in a glucose-dependent manner, which is why they were originally developed for type 2 diabetes management.

These injections are administered subcutaneously, with doses typically titrated upwards over several weeks. Semaglutide (Wegovy) is given once weekly, while liraglutide (Saxenda) requires daily administration. In the UK, NICE specifically recommends semaglutide (TA875) for adults with a BMI ≥35 kg/m² (or ≥30 kg/m² for certain ethnic groups) who have at least one weight-related comorbidity, with treatment limited to a maximum of 2 years. NICE does recommend liraglutide (Saxenda) as an option for managing overweight/obesity in adults in Tier-3 services and with specific BMI criteria (TA664).

Both medications are intended as adjuncts to a comprehensive weight management programme that includes dietary modification, increased physical activity, and behavioural support. They work most effectively when combined with lifestyle changes rather than as standalone treatments. Contraindications include a personal or family history of medullary thyroid carcinoma and multiple endocrine neoplasia syndrome type 2, with caution advised in those with a history of pancreatitis.

Why Some People Feel Cold During Weight Loss Treatment

Feeling cold during weight loss treatment is a phenomenon reported by some patients, though it's important to understand the multiple potential contributing factors rather than attributing it solely to the medication itself. The sensation of coldness during weight reduction can arise through several physiological mechanisms.

Reduced metabolic rate is a primary consideration. As body weight decreases, the body's overall energy expenditure naturally declines because there is less tissue to maintain. This metabolic adaptation, sometimes called "adaptive thermogenesis," means the body generates less heat as a byproduct of cellular metabolism. This is a normal physiological response to weight loss regardless of the method used to achieve it, as documented in systematic reviews of energy expenditure during weight reduction.

Loss of insulating adipose tissue plays a significant role. Body fat serves as insulation, helping to maintain core body temperature and reduce heat loss to the environment. As subcutaneous fat decreases during weight loss, this insulating layer becomes thinner, potentially making individuals more sensitive to environmental temperatures. People who lose substantial amounts of weight often notice they feel colder in situations that previously felt comfortable.

Caloric restriction itself can influence temperature regulation. When consuming fewer calories, the body may reduce non-essential energy expenditure, including heat production. Some patients using weight loss injections report eating considerably less than before treatment, which may contribute to feeling cold.

Changes in thyroid function have been observed in some studies of rapid weight loss, though there is no established causal link between GLP-1 receptor agonists and clinically significant thyroid dysfunction in humans. Nevertheless, the body's metabolic adjustments during weight loss can affect how efficiently heat is generated and conserved.

It's worth noting that feeling cold can also be caused by other conditions unrelated to weight loss, such as iron-deficiency anaemia, vitamin B12 or folate deficiency, or an underactive thyroid. If cold sensitivity persists or is accompanied by other symptoms, it's important to discuss this with your healthcare provider.

Temperature Changes: What the Evidence Shows

The scientific evidence regarding temperature changes specifically related to GLP-1 receptor agonist injections remains limited and somewhat inconclusive. Cold intolerance is not listed among the common adverse effects in the Summary of Product Characteristics for semaglutide (Wegovy) or liraglutide (Saxenda), which typically include gastrointestinal symptoms (nausea, vomiting, diarrhoea, constipation), injection site reactions, and headache.

The large-scale STEP clinical trials (Semaglutide Treatment Effect in People with Obesity), published in the New England Journal of Medicine and JAMA, did not report increased cold sensitivity as a significant adverse effect. However, patient experience reports and online forums suggest that some individuals do notice feeling colder during treatment. This discrepancy between formal trial data and patient-reported experiences may reflect several factors: cold sensitivity might not have been specifically monitored in trials, it may be attributed to weight loss rather than the medication, or it might affect only a subset of patients.

Research into metabolic effects of GLP-1 receptor agonists shows these medications can influence energy expenditure and substrate metabolism. The STEP trials demonstrated that semaglutide promotes greater fat loss than muscle loss, which may help preserve metabolically active tissue. Some studies suggest these medications may have modest effects on resting metabolic rate, though findings are inconsistent.

Comparative evidence from other weight loss methods shows that cold intolerance is commonly reported following bariatric surgery and with very low-calorie diets, supporting the hypothesis that the sensation relates primarily to the weight loss itself rather than the specific mechanism. Research in weight management has found that cold sensitivity often correlates with the magnitude of weight loss, regardless of method.

Currently, there is no robust evidence to suggest that GLP-1 receptor agonists directly impair thermoregulation through pharmacological action on temperature control centres in the hypothalamus. The European Medicines Agency's European Public Assessment Report (EPAR) for Wegovy does not highlight thermoregulatory concerns as a safety signal. The sensation of coldness appears more closely linked to the metabolic and physical changes accompanying weight reduction.

Managing Cold Sensitivity While Using Weight Loss Injections

If you experience increased cold sensitivity during weight loss treatment, several practical strategies can help you maintain comfort whilst continuing your therapeutic programme. These approaches focus on supporting your body's temperature regulation without compromising your weight management goals.

Layered clothing is particularly effective, allowing you to adjust insulation according to your environment and activity level. Natural fibres such as wool and cotton provide good insulation whilst allowing moisture to escape. Thermal undergarments can be worn discreetly under regular clothing. Pay particular attention to extremities—hands, feet, and head—as these areas lose heat rapidly. Quality gloves, warm socks, and hats can significantly improve overall comfort.

Maintaining adequate nutrition within your reduced calorie intake is essential. Ensure you're meeting the minimum calorie recommendations provided by your healthcare team. Protein intake is particularly important, as the thermic effect of protein (the energy required to digest and process it) is higher than that of carbohydrates or fats, contributing to heat production. Include warm foods and beverages throughout the day, such as soups, herbal teas, and warm meals. If cold sensitivity persists, consider discussing with your healthcare provider whether you should be tested for iron, vitamin B12, or folate deficiencies.

Regular physical activity generates body heat and helps maintain muscle mass, which is metabolically active tissue that contributes to baseline heat production. The UK Chief Medical Officers' Physical Activity Guidelines recommend at least 150 minutes of moderate-intensity activity weekly, plus muscle-strengthening activities on at least two days. Exercise also improves circulation, helping distribute warmth throughout the body.

Environmental adjustments at home and work can make a significant difference. Slightly increasing room temperature, using a small personal heater, or employing heated blankets during sedentary activities can improve comfort.

Monitoring your overall wellbeing is crucial. Keep a symptom diary noting when cold sensitivity occurs, its severity, and any associated symptoms. This information will be valuable if you need to discuss concerns with your GP. Ensure you're staying well-hydrated, as dehydration can impair temperature regulation.

When to Speak to Your GP About Side Effects

While mild cold sensitivity during weight loss is generally not concerning, certain warning signs warrant prompt medical attention . Understanding when to seek professional advice ensures your safety whilst using weight loss injections.

Contact your GP or prescribing clinician if you experience cold intolerance accompanied by other symptoms that might suggest thyroid dysfunction, such as:

• Extreme fatigue or weakness that interferes with daily activities

• Unexplained weight gain or cessation of weight loss despite adherence to treatment

• Significant hair loss or changes in hair texture

• Persistent constipation unresponsive to usual measures

• Dry, flaky skin or changes in skin texture

• Muscle aches, cramps, or weakness

• Slowed heart rate

• Depression or significant mood changes

• Cognitive difficulties, including memory problems or difficulty concentrating

These symptoms could indicate hypothyroidism, which requires investigation through thyroid function tests (TSH, free T4). Whilst there is no established causal link between GLP-1 receptor agonists and acquired hypothyroidism, weight loss itself can sometimes unmask underlying thyroid conditions.

Seek urgent medical attention (call NHS 111 or 999 for severe symptoms) if you experience:

• Severe, persistent abdominal pain, especially in the upper right quadrant (potential pancreatitis or gallbladder disease)

• Yellowing of the skin or eyes (jaundice)

• Signs of dehydration or significantly reduced urine output

• Symptoms of hypoglycaemia (particularly if you're taking insulin or sulfonylureas for diabetes)

• Allergic reactions (rash, swelling, difficulty breathing)

• Visual changes or severe headaches (especially if you have diabetes with pre-existing retinopathy)

You should also discuss with your healthcare provider if cold sensitivity significantly impacts your quality of life, even without other concerning symptoms. Your prescriber can review your overall response to treatment, assess whether dose adjustment might be appropriate, and ensure your weight loss is occurring at a safe, sustainable rate. Regular monitoring during weight loss treatment typically includes weight, blood pressure, and assessment of any adverse effects.

Never discontinue prescribed medication without consulting your healthcare provider, as abrupt cessation may lead to rapid weight regain and loss of metabolic benefits achieved during treatment.

Frequently Asked Questions