Help protect children from gaming harms.

Take our survey

Please or to access all these features

Weight loss injections/treatments

Discuss weight-loss injections and treatments, including personal experiences. Mumsnet hasn't checked the qualifications of anyone posting here. You may wish to speak to a medical professional before starting any treatments.

Using pen after 1 month of being open

5 replies

Elfie23 · 25/07/2026 08:33

Hi.
Ive been reading some threads about micro dosing etc and wonder how this works with the ‘rule’ about using up a pen within 1 month of opening it?

I ask as I’ve just got a 5mg pen to use leading up to my holiday, but I still have one dose left in my 2.5mg pen. I want to get started on the 5mg but equally don’t want to waste the last of the 2.5mg! I have just under 4 weeks till my holiday and want to shift the last stubborn 10lbs or as much of it as I can!

So - if I don’t use the last 2.5mg now when is it safe to leave it till?

OP posts:
BalakayAARon · 25/07/2026 08:45

When are you planning to use it if you move up to 5mg? If you are happy to calculate doses/ click count, you could use it up now and take the remainder of the dose from the next pen.

How long have you been on 2.5mg?

Have you had 4 doses from it already, and are asking about the extra dose, or 3 doses taken out of 4?

Have you kept the pen in the fridge throughout?

Personally, I am happy to stretch longer than 30 days if the pen is kept in the fridge throughout using excellent hygiene practices, and the liquid remains clear. I do not keep dregs to use up sometime later. I finish the pen before moving on to the next one. This can occasionally mean taking some of the dose from the end of one pen and some from the new one.

KrazyKatty · 25/07/2026 08:46

Why don’t you want to use the last drops in the 2.5mg pen before starting the 5mg pen? Do you have the old style pen with the golden dose? You can use an insulin syringe to extract the rest of the medication.

Also, if you’re still getting good suppression at 2.5mg, there’s no need to jump up to 5mg from 2.5mg. You could always go up in increments of 0.5mg to reduce the risk of severe side effects. I’m still only on 3.75mg after 10 months and over 4 stones lost.

If you keep the pen in the fridge, it will last much longer than 4 weeks. Posters on MJ for a while who are in maintenance mode and titrating down are using higher dose pens such as 10mg and taking small doses by click counting and pens are lasting 8-12 weeks. Obviously, that’s well outside the manufacturers guidelines so you do so at your own risk.

AmberLime · 25/07/2026 09:44

So - if I don’t use the last 2.5mg now when is it safe to leave it till?

With thought and consideration for hygiene, many people use pens for longer than 1 month. It is generally expected that when doing this

  1. The pen is stored in the fridge throughout
  2. You wipe the seal and glass of the pen before and after each use using the alcohol wipes.

Doing these things minimises the risks.

If you have not done these things with your pen, then I would not suggest you 'save' the last dose in your 2.5mg pen.

Instead I would suggest you either use the 2.5mg doses and extract the bonus dose using a syringe (if your pen has a bonus dose) to make up 5mg

Or to use the 2.5mg while knowing it's not enough for a week - jab the last 2.5mg early, 3-4 days after your last jab, and then move to 5mg 3-4 days after that.

WeAllHaveWings · 25/07/2026 10:13

I wouldn't leave part pens lying about. Realistically when you go up to 5mg when would you plan to use the 2.5mg? I would either -

  • Extract as much as possible from the 2.5mg pen and use it. Perhaps inject first 5mg pen the following week a day or two early if really struggling to keep to calorie deficit during the week.
or
  • Extracts as big a dose as possible from the 2.5mg pen and inject. Carefully calculate how much mg you need to add up to a full 5mg dose and click count to take that mg from the 5mg pen.

Personally I'd go with the first, as if you extract from your new pen to make the dose up to 5mg this week it leaves you short on your last dose of your 5mg pen.

Elfie23 · 25/07/2026 19:15

I always keep the pens in the Fridge and wipe them with the sterile wipes provided.

I was on MJ for about 9 months last year, highest I got to was 7.5mg but to be honest couldn’t tell the difference between that and 5mg.
I stopped and put a little back on and want to shift it before my holiday. I’ve been using 2.5mg for a couple of months now but I do find myself snacking but with 5mg I never did and wasn’t that bothered about mealtimes so thought I’d have a boost for the next few weeks.

Ive got one dose left in the 2.5mg, I’ve never done the clicks or extracted it with a syringe as I don’t fully understand it and didn’t want to end up ill or anything xx

OP posts:
New posts on this thread. Refresh page