So… When Do Weight Loss Injection Side Effects Actually Start?

Here’s the tricky part: Week 1 might feel like nothing. You might feel completely normal on Day 1, Day 2… even all the way to Day 7.

That doesn’t mean your medication isn’t working. GLP-1s build gradually. Some side effects and benefits don’t show up until Week 2 or 3. Everyone’s different.

Nausea

Probably the most talked-about side effect. For some, it’s mild queasiness after eating. For others, it feels like morning sickness that comes and goes.

• Often triggered by rich, greasy, or sugary food

• Usually worse in the evenings or after bigger meals

• Can be eased by eating slowly and sticking to lighter meals

Fatigue

A lot of people report feeling unexpectedly wiped out in the first week.

• It might be your body adjusting to reduced calorie intake

• It can also be related to hydration (or lack of it)

• Try to rest when you can, it usually improves quickly

Burping and Bloating

It starts off subtle, then gets weirder.

• Air gets trapped more easily in your stomach as digestion slows down

• Burps may start to smell a bit sulphuric (gross but common)

• Bloating can make you feel full quicker or cause discomfort

Pro tip: Gentle movement and smaller meals can help.

Constipation

It’s not glamorous, but it’s very common.

• Bowel movements may slow down in your first week

• The longer food stays in your system, the harder it can get

• Hydration and fibre can help, but more on that in future posts

Weird Food Aversions

Don’t be surprised if something you normally love suddenly makes you gag.

• Coffee, eggs, and meat are common triggers

• The smell or texture might suddenly feel “off”

• This usually passes, but listen to your body in the meantime

Headaches and Dizziness

Often tied to eating less, drinking less, or adjusting blood sugar levels.

• Try sipping water regularly throughout the day

• Make sure you’re eating something, even if your appetite is low

Injection Site Reactions

A little redness or itching after injecting is nothing to worry about.

• Make sure you’re rotating injection sites

• Use alcohol wipes before and after

• If it becomes hot, swollen, or painful, speak to your prescriber