Learning how to inject weight loss medication correctly is essential for safe, effective treatment and optimal results. Injectable weight loss medications, primarily GLP-1 receptor agonists such as semaglutide (Wegovy) and liraglutide (Saxenda), are prescribed within specialist weight management services across the UK for eligible adults with obesity and weight-related health conditions. These subcutaneous injections are designed for self-administration at home following proper training. This comprehensive guide covers preparation, injection technique, site rotation, side effect management, and safe storage to help you confidently manage your treatment as part of a structured weight management programme that includes dietary changes, physical activity, and behavioural support.

Understanding Injectable Weight Loss Medications

Injectable weight loss medications represent a significant advancement in the management of obesity and weight-related health conditions. In the UK, the most commonly prescribed injectable medications belong to a class called glucagon-like peptide-1 (GLP-1) receptor agonists, which include semaglutide (Wegovy) and liraglutide (Saxenda). These medications work by mimicking a naturally occurring hormone that regulates appetite and blood sugar levels.

The mechanism of action involves slowing gastric emptying, which helps you feel fuller for longer periods, and acting on areas of the brain that control appetite. This dual action can lead to reduced calorie intake and, when combined with lifestyle modifications, clinically significant weight loss. According to NICE guidance, these medications are typically prescribed within specialist weight management services. Eligibility criteria vary by medication, but generally include adults with specific BMI thresholds and weight-related health conditions, alongside participation in a structured weight management programme.

These medications are administered via subcutaneous injection, meaning the medication is delivered into the fatty tissue just beneath the skin rather than into muscle or veins. Wegovy (semaglutide) is administered as a once-weekly single-dose pen, while Saxenda (liraglutide) requires daily administration using a multi-dose pen. Both are designed for patient self-administration at home after proper training.

It is essential to understand that injectable weight loss medications are not a standalone solution. They are most effective when used as part of a comprehensive weight management programme that includes dietary modifications, increased physical activity, and behavioural support. Regular reviews with healthcare professionals are required to assess progress, with specific stopping rules if insufficient weight loss occurs (typically <5% body weight after 12 weeks at the maintenance dose).

Preparing for Your Injection: What You Need

Proper preparation is crucial for safe and effective administration of injectable weight loss medication. Before each injection, gather all necessary supplies and ensure you have a clean, well-lit area to work in. You will need:

• Your prescribed medication pen (check it has been stored correctly)

• Alcohol wipes or cotton wool with surgical spirit

• A sharps disposal container (available on prescription or via local council services)

• Clean, dry hands

Before handling your medication, wash your hands thoroughly with soap and warm water for at least 20 seconds, then dry them completely. Inspect the medication pen carefully—check the expiry date on the label and examine the solution through the viewing window. The liquid should be clear and colourless. Do not use the pen if the solution appears cloudy, discoloured, or contains particles, or if the pen appears damaged.

Remove the medication from the refrigerator approximately 30 minutes before injection to allow it to reach room temperature, as injecting cold medication can cause discomfort. However, do not attempt to warm it artificially using hot water or a microwave. Check your prescription label to confirm the correct dose, particularly if your healthcare provider has recently adjusted your dosage.

Ensure you have your sharps bin readily accessible—never dispose of needles in household waste. If this is your first injection or you are using a new pen device, read the patient information leaflet thoroughly and follow the device-specific preparation steps. For Saxenda pens, you'll need to prime a new pen before first use, while Wegovy comes as a pre-set single-dose pen. Many patients find it helpful to set a regular time for their injections to establish a routine and reduce the likelihood of missed doses.

Step-by-Step Guide to Injecting Weight Loss Medication Safely

Administering your injectable weight loss medication correctly ensures optimal absorption and minimises discomfort. Follow these steps carefully, noting that specific details may vary between Wegovy (semaglutide) and Saxenda (liraglutide) devices:

Step 1: Select and prepare your injection site. Choose an area with adequate subcutaneous fat—typically the abdomen (at least 5cm away from the navel), front of the thighs, or upper arms. Clean the chosen site with an alcohol wipe using a circular motion, working outward from the centre, and allow the area to air dry completely for at least 10 seconds.

Step 2: Prepare the pen device. Remove the pen cap and attach a new needle according to the manufacturer's instructions. Most pens require you to remove both the outer and inner needle caps. For Saxenda multi-dose pens, perform a flow check (priming) with a new pen by dialling a small dose and pressing the injection button until a drop of medication appears at the needle tip. Wegovy single-dose pens do not require priming.

Step 3: Set your dose. For Saxenda, turn the dose selector to your prescribed dose, checking carefully that the correct number appears in the dose window. Wegovy pens come pre-set with the correct dose and do not require adjustment.

Step 4: Perform the injection. If you have limited subcutaneous tissue, pinch a fold of skin gently between your thumb and forefinger to lift the tissue away from underlying muscle. Insert the needle at a 90-degree angle using a quick, dart-like motion. Press the injection button fully and hold it down while counting according to your device's instructions (typically 6 seconds for Saxenda; until the counter shows '0' and you hear or feel a click for Wegovy). Release the button, then withdraw the needle straight out.

Step 5: Complete the process. Do not rub the injection site. Carefully remove the needle from the pen and dispose of it immediately in your sharps container. Replace the pen cap and store the pen as directed in your patient information leaflet. Record the injection in a diary or app if you find this helpful for tracking. Never share your pen or needles with another person, even if the needle has been changed.

Injection Site Selection and Rotation

Proper injection site selection and systematic rotation are essential practices that help prevent complications and ensure consistent medication absorption. Using the same injection site repeatedly can lead to lipohypertrophy (thickening or lumps in the fatty tissue) or lipoatrophy (loss of fatty tissue), both of which can affect how well your medication is absorbed and may cause discomfort.

The three recommended injection sites for subcutaneous weight loss medications are:

• Abdomen: The preferred site for many patients, offering a large surface area. Inject at least 5cm (approximately two finger widths) away from the navel and avoid areas with scars, moles, or stretch marks.

• Thighs: Use the front and outer aspects of the thighs, in the middle section between the hip and knee. Avoid the inner thigh where there are more blood vessels and nerves.

• Upper arms: The back of the upper arms can be used, though this site may be more difficult to reach for self-injection and is best administered by another person.

Develop a systematic rotation pattern to ensure you change the injection site with each dose. Rotate both within a region (e.g., different areas of the abdomen) and between regions (e.g., abdomen to thigh). Keep each new injection at least 1-2cm away from the previous injection site. Some patients find it helpful to keep a simple diagram or use a smartphone app to track their injection sites.

Avoid injecting into areas that are tender, bruised, red, hard, or scarred, as these conditions can affect absorption and increase discomfort. If you notice any persistent lumps, nodules or changes in the skin at injection sites, inform your healthcare provider promptly.

Common Side Effects and When to Seek Medical Advice

Injectable weight loss medications are generally well-tolerated, but like all medicines, they can cause side effects. Understanding what to expect and recognising warning signs that require medical attention is crucial for safe use.

Common gastrointestinal side effects are the most frequently reported and typically include nausea, vomiting, diarrhoea, constipation, and abdominal discomfort. These effects are usually most pronounced when starting treatment or increasing the dose, and often improve over time as your body adjusts. To minimise these symptoms, eat smaller, more frequent meals, avoid high-fat foods, and stay well-hydrated. If nausea is troublesome, try taking the injection in the evening or discuss anti-nausea medication with your GP.

Injection site reactions such as mild redness, itching, or bruising are common and usually resolve within a few days. Applying a cold compress after injection may provide relief. However, if you develop significant swelling, persistent pain, or signs of infection (increasing redness, warmth, or discharge), contact your healthcare provider.

Seek urgent medical advice or attend A&E if you experience:

• Severe, persistent abdominal pain, particularly if radiating to the back (potential sign of pancreatitis)

• Persistent vomiting preventing fluid intake (risk of dehydration and acute kidney injury)

• Signs of allergic reaction: difficulty breathing, swelling of face or throat, severe rash

• Symptoms of gallbladder problems: yellowing of skin or eyes, fever with abdominal pain

• Severe palpitations or significant heart rhythm disturbances

Contact your GP or specialist team if you experience persistent side effects that do not improve, unexplained weight loss that seems excessive, or if you have concerns about your medication. If you have diabetes and notice changes in vision, seek prompt review from your GP or ophthalmology service.

These medications should not be used during pregnancy or breastfeeding. If you are of childbearing potential, use effective contraception while on treatment. For semaglutide, discontinue at least 2 months before a planned pregnancy.

You can report suspected side effects to the MHRA through the Yellow Card scheme at yellowcard.mhra.gov.uk. Never stop taking your medication without consulting your prescriber first.

Storage and Disposal of Injectable Weight Loss Medications

Proper storage and disposal of injectable weight loss medications are essential for maintaining medication efficacy and ensuring public safety. Incorrect storage can render the medication ineffective, whilst improper disposal poses risks to others and the environment.

Storage requirements vary by product:

• Wegovy (semaglutide): Unopened pens must be stored in a refrigerator at 2–8°C. Keep them in the original carton to protect from light. As a single-dose pen, it should be used immediately after preparation or discarded according to the patient information leaflet.

• Saxenda (liraglutide): Unopened pens must be refrigerated at 2–8°C. Once in use, the pen can be stored either in the refrigerator or at room temperature (below 30°C) for up to 30 days.

For both medications:

• Do not freeze; discard if accidentally frozen.

• Always store pens with the cap on to protect from light and contamination.

• Keep medications out of reach of children and pets.

• Do not store pens with the needle attached, as this can cause air bubbles and potential leakage.

When travelling, use a cool bag with ice packs (ensuring the medication does not come into direct contact with ice). Carry your medication in hand luggage when flying, along with your original packaging and a copy of your prescription or a letter from your prescriber if travelling internationally.

Safe disposal is a critical aspect of medication management. Used needles must never be placed in household waste or recycling bins. Immediately after each injection, place the used needle into a sharps container—a rigid, puncture-proof container specifically designed for this purpose. These are available on prescription or through local council services, though provision varies by area. When your sharps container is three-quarters full, seal it according to the instructions and follow local guidance for return or collection—this may involve your pharmacy, GP surgery, or local council waste services.

Dispose of expired or unused medication pens by returning them to your pharmacy—do not throw them in the bin or flush them down the toilet. If you accidentally stick yourself with a used needle, wash the area immediately with soap and water and seek medical advice from your GP or local urgent care centre.

Frequently Asked Questions