Woman who lost six stone taking Mounjaro shares biggest side effects she has faced

Mounjaro and Ozempic success stories are everywhere you look, with people sharing what seems to be effortless weight loss.

One woman has been documenting the reality of her experience with Mounjaro, which has led to her losing an impressive six stone so far.

Posting as @insightfullucy, the TikTok star has been updating fans about her experience with the GLP-1 medication.

Mounjaro was originally formulated to help treat diabetes, but has since become a household name for those trying to shed the pounds.

The prescription-only medication is now set to be rolled out on the NHS along with a similar drug, called Wegovy.

Lucy Davies has been sharing the highs and lows of her weight loss since she first started taking the drug back in September 2024.

She has now shared a video detailing some of the biggest side effects she has faced while taking the medication.

How does Mounjaro work?

Mounjaro uses the active ingredient tirzepatide, to work to as an appetite suppressant.

It also slows down the digestion of food in your stomach, causing it to move more slowly throughout your system, causing you to feel fuller for longer.

The drug works by mimicking two hormones, glucose‐dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1).

These hormones are used to stabilise blood sugar levels and reduce appetite.

Users work their way up in dosages, usually starting from 2.5mg, to increase the amount of appetite suppression as they go.

Here are some of the side effects Lucy says she has been experiencing while on the medication.

Tiredness and fatigue

Lucy explained that the side effects have been different for each dosage amount of Mounjaro, but one of the most consistent has been tiredness.

"The tiredness, that's been massive right from the beginning. As soon as I take a dose, for two days after the dose I am just wiped out," she confessed.

"It tops it all. The first time I took the 2.5mg I was drained, I slept for three days, so for me the biggest symptom was definitely tiredness."

Viewers agreed with her in the comments, writing: "Day 6 and I feel like my batteries have run out!"

However, one replied saying she suffers from chronic fatigue but Mounjaro has given her 'more energy than I've had in years.'

Nausea

One of the most commonly complained about side effects seems to be sickness and nausea.

"Nausea has been one of the biggest ones for me," revealed Lucy.

"Especially a couple of days after the dose, the feeling of sickness is quite strong, that does subside though."

"I'd say it only lasts about two days after you've taken the dose but after that, then it's gone."

One viewer agreed: "After I've taken my dose I'm sick for 3-4 days after, it's awful."

"I'm on my 7th week and never really had any symptoms, today, the day after, I feel so so nauseous" said one commenter.

Headaches

As well as tiredness and feeling sick, Lucy found there was another side effect she usually noticed upon waking.

"I tend to wake up with headaches a lot, but once I've drunk water I seem to be fine."

"Headaches don't seem to be as bad now," she advises. "In the beginning they were quite bad, but they seem to have eased off now, but that's another side effect."

Feeling cold

Despite the scorching heatwave we've been having, Lucy said she was still feeling chilly.

She explained: "I don't seem to have this as much now but on 2.5mg and 5mg I had that a lot, I was constantly freezing."

Commenters were relieved to know they're not the only ones experiencing this: "I thought I was the only one being freezing cold all the time even when it's hot outside!"

Constipation

"The final one is constipation, this is manageable, just eating more fibre," she explains.

Many users have been complaining about this side effect online, thanks to Mounjaro's ability to slow down your digestive system. It's causing people to get backed up if they're not careful.

Speaking about supplements, she said: "I have had to take the odd fibre gel but that's absolutely fine, but the biggest ones for me were definitely the tiredness, the nausea and the headaches."

One lucky commenter replied saying they had no side effects at all, and have actually never felt better.