Most people on GLP-1 weight loss medicines get some nausea, constipation or tiredness — usually mild, usually temporary, and usually manageable with the practical steps below. A smaller set of symptoms needs prompt medical attention, and we've been just as clear about those.
Reviewed by Orali · Clinical Lead — a GPhC-registered Pharmacist Independent Prescriber · Last updated 12 June 2026
GLP-1 medicines — tablet or injection — slow stomach emptying and act on appetite centres in the brain. That's how they work, and it's also why the common side effects are digestive: food sits longer, the gut moves slower, and you eat substantially less than your body is used to. Side effects cluster around starting treatment and each dose increase, then typically fade as your body adapts. This is why prescribers start low and titrate slowly — and why side effects are a dosing conversation, not something to white-knuckle through alone.
Most common in the first days after starting or increasing a dose · usually settles within a few weeks
Talk to your prescriber if: nausea is severe, lasts beyond a few weeks, or you can't keep fluids down. Dose schedules can be slowed or adjusted — that's normal practice, not a failure.
Builds gradually · affects roughly a quarter of people at some point during treatment
Talk to your prescriber if: constipation is persistent or painful, you have no bowel movement for several days despite the above, or you notice blood. Don't simply stack stronger laxatives on your own.
Common in the early months · usually reflects how much less you're eating
Talk to your prescriber if: fatigue is worsening rather than settling, or it's paired with dizziness, palpitations or fainting — especially if you also take diabetes or blood pressure medicines, which may need adjusting as you lose weight.
For any of these, contact your prescriber, your GP, or NHS 111 the same day — or 999 for breathing difficulty or collapse. Orali patients have a direct line for side effect concerns; using it is never an overreaction.
For most people, the rough patch is the first one to three weeks after starting and after each dose increase, settling as the body adapts. Side effects that persist beyond that, or get worse rather than better, are a reason to speak to your prescriber — often the answer is simply a slower titration.
Don't stop abruptly on your own unless you have one of the urgent symptoms above. Mild nausea is expected and manageable, and stopping and restarting can mean retitrating from scratch. Contact your prescriber first — adjusting the dose plan is usually enough.
Broadly similar — the digestive side effects come from the GLP-1 mechanism itself, not the format. What differs is dosing flexibility and individual response. Our pill vs injection guide covers the full comparison.
There's no absolute ban, but alcohol hits harder on a slower-emptying stomach and an emptier one, and it worsens nausea, reflux and dehydration. Many people find their tolerance noticeably lower. Go gently, and ask your prescriber about your individual situation — especially if you take diabetes medicines.
Every Orali treatment plan includes scheduled reviews and a direct line for side effect concerns — because treatment without follow-up is poor care. If you're considering treatment, start with the free eligibility check.
Start the free eligibility checkA consultation never guarantees a prescription — if treatment isn't right for you, we'll say so.