As more[1] weight loss injection users are taking up micro-dosing, Pharmacists are becoming increasingly concerned about the potential repercussions. Namely, the significant hygiene problems that can occur from reusing the same needle several times, as patients look to make one pen last.

With a +5,000% increase in UK searches over the past month for “microdosing Mounjaro”, many are not aware of the health implications that could come from taking less than their prescribed dose.

Jason Murphy, Head of Pharmacy and weight loss injection expert at Chemist4U, commented:

“There has been an increase in weight loss injection users experimenting with their dosing, such as microdosing to make pens last longer. While there isn’t much research into the potential benefits of taking more, smaller doses, it is possible that not taking the recommended dose could exacerbate side effects and come with other, unknown risks. For any medication, you should always read the instructions carefully and stick to taking the correct amount.

“By making your dose last longer, there’s also more risk of your medication expiring: for Mounjaro, that’s 30 days after opening, and potentially up to 24 months if kept in the right conditions sealed (refrigerated between 2 and 8 degrees). Always check the expiry on the box to be sure: taking it after it expires is likely to make the medication ineffective.

“One of the greatest problems that can arise from micro-dosing is needle reuse. Those taking smaller doses will need more injections, and this comes with several serious health risks if you’re not also replacing your needle each time.”

To shed light on the serious health risks that could come with reusing needles, Chemist4U reveal the potential issues such as infection, tissue damage, inaccurate doses and compromised results.

The dangers of needle reuse

Jason Murphy, Head of Pharmacy and weight loss injection expert at Chemist4U, commented:
“The biggest concern around microdosing is that many don’t realise how dangerous it is to reuse a needle.

“Once a needle has pierced your skin, it becomes blunted, harbours bacteria, and it doesn’t deliver the medication as accurately. This can lead to users experiencing bruising, inflammation, and inconsistent results with their treatment, often because they’re not using a fresh needle each time.”

Bacterial contamination

Even a single reuse of a needle can lead to harmful bacteria build-up directly under your skin. This increases the risk of painful infections, redness, swelling, and can even require medical attention. As needles are not sterile after use, each injection with a reused needle creates an opportunity for bacteria to enter your body, putting your health at serious risk.

Blunt needles

Once a needle has pierced your skin, it loses its sharpness, making subsequent injections more painful. Blunt needles can tear tissue instead of delivering the medication smoothly, often leaving bruising and soreness. Over time, repeated use of dull needles can create lasting tissue irritation, making future injections more uncomfortable and potentially more difficult to carry out.

Inaccurate dosing

A used needle can accumulate residue or become partially blocked, which can prevent the full dose of medication from being delivered. This can lead to inconsistent results, meaning you might receive less medication than intended, slowing progress or making side effects less predictable.

If you’re microdosing, even small variations in dose can have a bigger impact on the effectiveness and safety of your treatment. So, important to stick to the recommended dose so results are as effective as possible.

Lipohypertrophy

Repeated injections on the same area, especially with a reused needle, can cause lipohypertrophy, which is a build-up of lumpy, scarred tissue under the skin.

These hardened patches interfere with how well your medication is absorbed, which can reduce effectiveness and make injections more painful. Once lipohypertrophy develops, it can take time to heal, and you will need to rotate injection sites carefully to avoid further complications.