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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.

Feel so ill after first dose 😪

57 replies

FishersGate · 25/07/2026 10:06

First jab yesterday morning by 5pm I felt awful, sick lethargic headache no appetite. Had a small meal felt a little better. Woke up with a banging headache, chronic nausea. Small amount of sickness had two spoonfuls of over night oats. Had to get back into bed.

Does this pass? I am so upset I have so many friends who didnt suffer side effect 😔

I am going away in 3 weeks amd dont want to feel like this 😞.

For context 15stone and 5 5. Have FH and a few other conditions so need to get weight off.

OP posts:
SilenceInside · 25/07/2026 10:21

Sounds like you’re particularly sensitive to the medication which can happen. The medication peaks in your system between 8 to 72 hours after injecting and then gradually falls away until half of the medication is gone by the end of the week. Assuming this is Mounjaro? Wegovy is similar though.

Side effects are associated with starting treatment and with going up dose. They tend to generally improve over the longer term.

If you are still feeling rough by the time of the next injection you could delay it for a few days. You could also consider doing a half dose rather than a full dose from the pen.

Velvetandleather · 25/07/2026 10:24

SilenceInside · 25/07/2026 10:21

Sounds like you’re particularly sensitive to the medication which can happen. The medication peaks in your system between 8 to 72 hours after injecting and then gradually falls away until half of the medication is gone by the end of the week. Assuming this is Mounjaro? Wegovy is similar though.

Side effects are associated with starting treatment and with going up dose. They tend to generally improve over the longer term.

If you are still feeling rough by the time of the next injection you could delay it for a few days. You could also consider doing a half dose rather than a full dose from the pen.

That’s not correct, it’s 24 - 72 hours.

spunds like you can’t tolerate the medicine op, so will need to stop. If after a few hours before it’s even peaked you’re so unwell. You could try wegovy.

there is one question though, do you suffer health anxiety?

GaaNeen · 25/07/2026 10:24

Yes it passes,
hang on in there -
if it persists, try a half dose next time

WeAllHaveWings · 25/07/2026 10:25

Hopefully it will pass, no one can say as it is very individual.

For the headache make sure you are getting enough hydration, and some food too as low blood sugar can cause headaches.

Chronic nausea, ask your local pharmacy what they can recommend.

Fatigue, try to get some calories in, high calorie/low volume foods, I snacked on mixed nuts a lot in the first few weeks (between meals, can't live on nuts alone!)

Hope you feel better soon.

WeAllHaveWings · 25/07/2026 10:27

Velvetandleather · 25/07/2026 10:24

That’s not correct, it’s 24 - 72 hours.

spunds like you can’t tolerate the medicine op, so will need to stop. If after a few hours before it’s even peaked you’re so unwell. You could try wegovy.

there is one question though, do you suffer health anxiety?

From Eli Lilly -

Absorption Following subcutaneous administration, the time to maximum plasma concentration of tirzepatide ranges from 8 to 72 hours.

SilenceInside · 25/07/2026 10:29

Perhaps there are some differences in how this is discussed online @Velvetandleather. Certainly plenty of sources state 8 to 72 hours eg https://www.harleystreetskinclinic.com/articles/how-long-does-mounjaro-take-to-work-a-comprehensive-guide-to-expectations/

https://www.theindependentpharmacy.co.uk/weight-loss/guides/your-first-month-on-mounjaro-what-to-expect

And a more academic source:

https://www.ncbi.nlm.nih.gov/books/NBK585056/

KrazyKatty · 25/07/2026 10:29

The good news is that you’ve had a definite response to your first dose! Some people don’t feel the effects until they reach the higher doses such as 7.5mg.

I had a similar response to you with headaches and feeling sick but I was feeling fine by about day 3. If you still feel crappy on day 4/5, consider dropping your next dose to 1.5mg or 2mg by counting clicks. You might be a super responder.

Also, the medicine isn’t gone by the end of the week! Be aware that MJ builds in your system so week 3 can be worse than week 1 for some people and you might want to take a half dose before your holiday if you are worried about severe side effects.

Gardenflowering · 25/07/2026 10:35

Same OP,

Everyone is of course different so hopefully it will settle down for you.

FishersGate · 25/07/2026 10:44

Velvetandleather · 25/07/2026 10:24

That’s not correct, it’s 24 - 72 hours.

spunds like you can’t tolerate the medicine op, so will need to stop. If after a few hours before it’s even peaked you’re so unwell. You could try wegovy.

there is one question though, do you suffer health anxiety?

Its mounjaro yes.

Yes I have had a bad week health wise, having had a long discussion with a consultant regarding familiar hyperchoelestimia and a lipid protein inheritance. High risk of stroke or heart attack. My cholesterol is 6, so high hence the need to get weight off. Struggling with peri menopause. Suffer adenomyosis and interstitial cystitis.

I put off taking this for 3 months due to side effects.

Its not anxiety causing this, apart from being tired I felt fine. Advice seems to be you can respond pretty quickly to the drug. Just a few friends had no side effects or perhaps they weren't saying!

Headaches and tiredness i can cope with l. Constant nausea 😵. Is not great

OP posts:
FishersGate · 25/07/2026 10:45

GaaNeen · 25/07/2026 10:24

Yes it passes,
hang on in there -
if it persists, try a half dose next time

Thank you ! I am trying to think positively regarding day 3 or 4 🤣

OP posts:
Itshotinherebutainttakingoffmyclothes · 25/07/2026 10:47

Sip loads of water. You need to take extra care to stay hydrated. You also need to focus on eating protein and veg. Carbs aren’t bad but they’re unnecessary at this point and are preventing you eating protein and veg and fruit which are essential.

Also try meds like gaviscon if you’re feeling sick.

FishersGate · 25/07/2026 10:47

KrazyKatty · 25/07/2026 10:29

The good news is that you’ve had a definite response to your first dose! Some people don’t feel the effects until they reach the higher doses such as 7.5mg.

I had a similar response to you with headaches and feeling sick but I was feeling fine by about day 3. If you still feel crappy on day 4/5, consider dropping your next dose to 1.5mg or 2mg by counting clicks. You might be a super responder.

Also, the medicine isn’t gone by the end of the week! Be aware that MJ builds in your system so week 3 can be worse than week 1 for some people and you might want to take a half dose before your holiday if you are worried about severe side effects.

Thank you. I have heard you aren't supposed to click 🫣. Due to not being able to confirm the dosage given etc. But it might be the way to go.

OP posts:
FishersGate · 25/07/2026 10:49

Gardenflowering · 25/07/2026 10:35

Same OP,

Everyone is of course different so hopefully it will settle down for you.

Ah horrid isn't it. Had the vision in my head of just carrying on as normal with no appetite 🤣

OP posts:
FishersGate · 25/07/2026 10:49

Itshotinherebutainttakingoffmyclothes · 25/07/2026 10:47

Sip loads of water. You need to take extra care to stay hydrated. You also need to focus on eating protein and veg. Carbs aren’t bad but they’re unnecessary at this point and are preventing you eating protein and veg and fruit which are essential.

Also try meds like gaviscon if you’re feeling sick.

Thanks I have been sipping water. I had already made overnight oats to make sure I had something to eat. Now sipping a protein shake to

OP posts:
Notellinganyone · 25/07/2026 10:53

FishersGate · 25/07/2026 10:45

Thank you ! I am trying to think positively regarding day 3 or 4 🤣

I’ve been on it since February and lost two stone so far. The first dose was tough for me but it settled down. I’ve actually stayed on the lowest dose happy to lose wrigh5 slowly and avoid side effects of rapid weight loss and of the drug itself. I definitely wouldn’t give up yet - read up on advice to mitigate side effects and good luck!

SilenceInside · 25/07/2026 10:56

It annoys me when the pharmacies try to suggest that counting clicks is inaccurate, although I realise why they can’t endorse it. There are 60 line markers on the Mounjaro pen, each makes a tiny click as you turn past it. Turning to the full 60 gives you a 0.6ml dose. Turning to 30 would therefore give you a 0.3ml dose. The only issue would be if you miscount significantly, which is unlikely if you take your time and double check what you’re doing. You can then mark the 30 point with a pen for next time.

Velvetandleather · 25/07/2026 10:58

Can I ask what you ate the day before your first injection?

Too much sugar and fat can cause gastro impacts. And not eating makes us feel sick, so it’s counter productive.

FishersGate · 25/07/2026 11:03

Velvetandleather · 25/07/2026 10:58

Can I ask what you ate the day before your first injection?

Too much sugar and fat can cause gastro impacts. And not eating makes us feel sick, so it’s counter productive.

I disagree with the day before but I had one weetabix with milk. Small iced decaf coffee. Sourdough bread with scrambled egg. One two finger kit kat l. Small chicken pasta dish with carrots broccoli.

I have been trying to eat Small amounts, even my dinner was very small last night

OP posts:
FishersGate · 25/07/2026 11:05

SilenceInside · 25/07/2026 10:56

It annoys me when the pharmacies try to suggest that counting clicks is inaccurate, although I realise why they can’t endorse it. There are 60 line markers on the Mounjaro pen, each makes a tiny click as you turn past it. Turning to the full 60 gives you a 0.6ml dose. Turning to 30 would therefore give you a 0.3ml dose. The only issue would be if you miscount significantly, which is unlikely if you take your time and double check what you’re doing. You can then mark the 30 point with a pen for next time.

Thank you. I agree. So is 1.25mg is that not 30 clicks ?

OP posts:
FishersGate · 25/07/2026 11:06

Notellinganyone · 25/07/2026 10:53

I’ve been on it since February and lost two stone so far. The first dose was tough for me but it settled down. I’ve actually stayed on the lowest dose happy to lose wrigh5 slowly and avoid side effects of rapid weight loss and of the drug itself. I definitely wouldn’t give up yet - read up on advice to mitigate side effects and good luck!

Thank you. I know its all new and getting used to it but I have to start statins too soon and wanted to get thos underway. Hopefully it will pass

OP posts:
SilenceInside · 25/07/2026 11:09

@FishersGate if you have a 2.5mg pen then the full 0.6ml dose would be 2.5mg, so 30 clicks would give you 0.3ml so yes that would be a 1.25mg dose.

A full dose from any strength pen is always 0.6ml or 60 clicks.

FishersGate · 25/07/2026 11:17

SilenceInside · 25/07/2026 11:09

@FishersGate if you have a 2.5mg pen then the full 0.6ml dose would be 2.5mg, so 30 clicks would give you 0.3ml so yes that would be a 1.25mg dose.

A full dose from any strength pen is always 0.6ml or 60 clicks.

Thank you. I will see how it goes in a day or so. But i guess I would have wastage from the pen? As its only open 30 days?

OP posts:
SilenceInside · 25/07/2026 11:23

@FishersGate ah well, it depends how you feel personally about going past that timeframe. For me, if the pen is always in the fridge and I am scrupulous with hygiene then I am flexible with that timeframe. With the caveat that if the liquid ever is cloudy or has particulates then not to use it. You can do five injections within the 30 days, the 6th would be a week after that. Whether you’d be ok with going past that is up to you.

FlorenceLawrence · 25/07/2026 12:07

I happily go over the 30 days - I've read the drug is good for 5-6 months as long as it's kept in the fridge. I always use an antiseptic wipe on the red seal before putting the needle on, and on the injection site.
If you can get through the initial side effects, they do lessen over time so it can be worth persevering.
Eating clean on injection day (I would judge chicken pasta too heavy personally, and would have swapped that for a chicken salad) and injecting in the evening helps me with side effects I did get a few at the beginning - including dizziness, headaches, nausea, tiredness, but I've been on it over a year now, and rarely have side effects now - occasional bout of diarrhea but that's usually down to eating something unwise! Eat as low-fat and low-carb as you can, and maximise protein & veg. Carry on eating the small portions.

FishersGate · 25/07/2026 12:09

FlorenceLawrence · 25/07/2026 12:07

I happily go over the 30 days - I've read the drug is good for 5-6 months as long as it's kept in the fridge. I always use an antiseptic wipe on the red seal before putting the needle on, and on the injection site.
If you can get through the initial side effects, they do lessen over time so it can be worth persevering.
Eating clean on injection day (I would judge chicken pasta too heavy personally, and would have swapped that for a chicken salad) and injecting in the evening helps me with side effects I did get a few at the beginning - including dizziness, headaches, nausea, tiredness, but I've been on it over a year now, and rarely have side effects now - occasional bout of diarrhea but that's usually down to eating something unwise! Eat as low-fat and low-carb as you can, and maximise protein & veg. Carry on eating the small portions.

Sorry the chicken pasta was the night before. Not the day! Yesterday I couldn't really eat. I am trying to eat now and even putting the spoon to my mouth is making me feel ill l. Urine is nice clear so not dehydrated

OP posts: