Weight-Loss Pen Not Clicking or Dosing? A Calm Checklist

If your weight loss pen is not clicking, or it clicked and you're still not sure the dose went in, pause before you do anything else. The two four-dose pens dispensed in the UK, the Mounjaro KwikPen and the Wegovy FlexTouch, give different feedback, and clicks are not how either confirms a dose. Here is what the sounds and symbols mean, and what the instructions say.

Why a weight-loss pen that isn't clicking is rarely broken

Much of the confusion comes from expecting one pen to behave like another. Single-dose pens such as the Wegovy 7.2 mg pen are pressed against the skin and show their own progress; the standard four-dose pens are manual: you dial, you push, you read a window.

• Mounjaro KwikPen. Lilly's instructions mention clicks once: as you slowly turn the dose knob you should hear 2 clicks and see an extended line in the dose window: the prime position. Dialling the dose is "turn until it stops" and a full-dose symbol appears; pushing the knob in is a counted hold, not a click.
• Wegovy FlexTouch. Novo Nordisk's leaflet says you hear a click each time you turn the dose selector, that it clicks differently forwards, backwards or past your dose, and that you must not set the dose by counting clicks. You may hear or feel a click when the counter returns to 0, but the counter is the proof.

Our Mounjaro pen and Wegovy pen pages describe each device; this comparison sets the routines side by side.

The calm checklist

Work through these in order.

1. Put the pen down

A quiet pen is not an emergency. The one mistake that can't be undone is a second injection on top of a dose that did go in, so stop and look first.

2. Check the needle before you blame the pen

When a pen seems to do nothing, both leaflets look at the needle and the technique before the pen. Both leaflets say to use a new needle for every injection, and both needle shields must be off. If a Mounjaro dose knob is hard to push, Lilly's advice is to push more slowly, then fit a new needle and prime again. Never store a KwikPen with a needle attached: it can leak, block the needle or let air in. Our needle guide covers single use and disposal.

3. Mounjaro: prime, then read the window

Lilly's instructions put priming before the injection itself. With a new needle on, slowly turn the dose knob to the 2-click prime position, hold the pen needle-up, tap the cartridge holder so air bubbles rise, then push the knob in until it stops and count slowly to 5, into the air. Medicine at the needle tip means it's working. If none appears, repeat no more than two further times, then change the needle and try once more; if that fails, the instructions say to contact the manufacturer.

For the injection, turn the knob until it stops and the full-dose symbol shows, insert the needle, push the knob in until it stops and hold for a slow count of 5. Then check the window for the completed-dose symbol pictured in the instructions. If it isn't there, put the needle back into your skin and finish without redialling; if you still think you missed some, Lilly says not to start over or repeat the injection.

4. Wegovy: flow check once, then trust the counter

The FlexTouch gets a flow check only before the first injection from each new pen. Turn the selector to the flow-check symbol, hold the pen needle-up and press the button until the counter shows 0; a drop should appear. If not, check again, twice at most, then change the needle and check once more. Still no drop? Do not use the pen.

When injecting, keep the counter visible (fingers over it can interrupt the injection), press and hold until it shows 0, then keep pressing for a slow count of 6. If 0 never appears despite continuous pressing, the leaflet says the needle may be blocked or damaged and you have not received any Wegovy, even though the counter moved: fit a new needle and set your dose again. A drop at the tip afterwards is normal.

5. The dial won't go all the way

If a KwikPen knob won't turn to the full-dose symbol, or a FlexTouch counter stops before your prescribed dose, there may not be enough medicine left for a full dose. Both manufacturers then say the same: dispose of the pen and don't inject the leftover. Each four-dose pen holds four weekly doses, and then it is finished.

6. Look at the pen itself

Don't use a pen that looks damaged, or whose medicine is cloudy, discoloured or has particles in it (Mounjaro should be colourless to slightly yellow; Wegovy clear and colourless), or one that may have frozen; take it back to the dispensing pharmacy. Novo Nordisk warns that rough handling can cause inaccurate dosing, so if a pen has been dropped or knocked hard, ask the pharmacy before using it. Our guide to storing weight-loss pens covers the temperature rules.

7. Still unsure? Ask before the next dose

Tell the dispensing pharmacist or your prescriber exactly what the window or counter showed. Both are once-weekly medicines: Mounjaro's leaflet says at least 3 days must separate two doses, and Wegovy's says never to take a double dose to make up for a missed one, so doubling up is never the safe default.

Faulty pens, unregulated pens and side effects

If you think the pen itself is faulty, tell the pharmacy that supplied it and, through them, the manufacturer. The MHRA's Yellow Card scheme takes reports of device problems as well as suspected side effects. Use only a pen prescribed for you and dispensed by a GPhC-registered pharmacy, and avoid unlicensed or "compounded" versions.

If the worry is how you feel rather than the pen: nausea, diarrhoea, constipation and vomiting are the most common side effects of both medicines. Our side effects page explains when to seek help; severe, persistent stomach pain needs urgent medical advice. Report suspected side effects via the Yellow Card scheme and tell your pharmacist or GP.

For the weekly routine and storage, see using your pen; more answers are in our FAQ and on the homepage.

Frequently asked questions

Related reading

• Mounjaro pen vs Wegovy pen: how the two devices differ
• Weight-loss pen needles: size, single use and disposal
• How weight-loss pens work: the device, not just the drug