Saxenda Side Effects Explained

Stomach-related side effects are common with liraglutide, particularly in the first weeks and after each increase in dose. For most people they ease. A small number of effects are serious and need medical help rather than patience, and knowing which is which before you start is the point of this page.

Important: PenCompare is an independent comparison platform, not a pharmacy or a prescriber. This page is general information and is not a complete list of side effects. The patient information leaflet supplied with your pen is the authority for your medicine. If you are unwell right now, contact a healthcare professional rather than reading on.

On this page

When to get urgent help

This is at the top rather than buried further down, because someone looking it up in a hurry should not have to scroll past a list of mild effects to find it.

Seek urgent medical help — call 999 or go to A&E

  • Severe stomach pain that will not go away, especially if it spreads through to your back, often with nausea and vomiting. This can be a sign of pancreatitis
  • Signs of a serious allergic reaction: swelling of the face, lips, tongue or throat, difficulty breathing or swallowing, a racing heartbeat, a rapidly spreading rash, or feeling faint

Do not message your online provider and wait for a reply. An online service is not set up to handle an emergency, and the time spent waiting is the thing that causes harm.

Contact your GP or NHS 111 promptly, rather than as an emergency, for pain in the upper right of your stomach with fever, yellowing of the skin or the whites of your eyes, or unusually pale stools. Those can point to a gallbladder problem, which is a recognised effect of this class of medicine.

Wait, ask, or act

  • Settles The common stomach effects usually ease over a few weeks as the body adjusts, and after each step up
    Worth mentioning at your next contact, but not a reason to stop on your own
  • Ask Contact your prescriber or pharmacist if it is not easing, or if it is stopping you eating or drinking normally
    NHS 111 can advise when you are unsure how urgent something is
  • 999 Severe or persistent stomach pain, or signs of a serious allergic reaction, need urgent medical help — not an online form
    Do not wait for a provider to reply to a message
Sorted by what to do rather than by how common each effect is, because frequency is not the useful question when something is already happening. The leaflet supplied with your pen is the authority for your medicine.

The common effects

Most of the frequently reported effects are gastrointestinal, which follows from how the medicine works: it slows the rate at which the stomach empties. Reported in more than 1 in 10 people:

  • Nausea
  • Diarrhoea
  • Constipation
  • Headache

Reported by up to 1 in 10 people: vomiting, indigestion, gastritis, stomach pain, heartburn, bloating and wind, tiredness, dizziness, a change in the sense of taste, low blood sugar, and reactions at the injection site.

A change in the sense of taste catches people off guard, since it is not what anyone expects from a weight-management medicine. Food tasting metallic or simply wrong is reported often enough to be listed, and it is not a sign that something has gone badly wrong.

What a daily injection changes

Side effects are usually at their worst in the first weeks and in the days after each step up, then settle as the body adjusts. With Saxenda that arrives faster than with the weekly pens: the dose rises every week rather than every four, so the whole step-up is compressed into about a month. See our dosage guide for how the steps work.

That cuts both ways, and it is worth knowing which way before you start. The difficult phase is shorter — but it is also more concentrated, with less time between increases for things to settle. If a week is rough, a prescriber can hold you at that dose rather than moving up on schedule, and that is a normal adjustment rather than a failure.

Injection site reactions also matter more here than with a weekly pen, for the plain reason that you are injecting seven times as often. Rotating sites rather than favouring one spot is the standard advice, and your pharmacist can show you what that looks like in practice.

Advice on easing the milder effects — smaller meals, eating slowly, plainer food, more fibre for constipation, keeping fluids up — is widely given and generally sensible. We are not going to dress it up as clinical guidance from a comparison site. Your pharmacist can tailor it to you, including checking it against anything else you take.

The serious ones

These are uncommon, and listing them is not a prediction. They are here because they are the ones where recognising what is happening early changes the outcome:

  • Pancreatitis — inflammation of the pancreas. The characteristic sign is severe, persistent stomach pain that often spreads through to the back
  • Gallbladder problems — including gallstones. Rapid weight loss from any cause raises this risk, so it is not unique to this medicine
  • Serious allergic reaction — rare, but it needs emergency treatment rather than a call-back
  • Dehydration and kidney problems — usually a consequence of prolonged vomiting or diarrhoea rather than a direct effect. Passing much less urine than usual is worth reporting
  • Low blood sugar — listed among the common effects here rather than the rare ones, and a particular concern for people also taking insulin or certain other diabetes medicines. Signs include shakiness, sweating, confusion and unusual irritability
  • Fast heartbeat — an increase in heart rate is recognised with this medicine and is worth mentioning to your prescriber if you notice it

Low blood sugar is worth a second look on this page in particular. It appears in the common list for liraglutide, not the rare one, and it is the effect most likely to be affected by what else you take. An assessment that never asked about your other medicines could not have accounted for it — and that is a fact about the service, not about you.

This is not the complete list. The leaflet supplied with your pen is, and it is written for the exact product you have been given. Most of what appears above is shared with the other medicines in this family — our guide to GLP-1 side effects across the class sets out what carries across and what does not.

Reporting a side effect

Suspected side effects can be reported to the MHRA through the Yellow Card scheme, by you as well as by a healthcare professional. It is how safety signals get spotted, and reports from patients count. Deal with being unwell first; report afterwards.

Frequently asked questions

For most people they ease over days or weeks as the body adjusts, and the pattern tends to repeat in a milder form after each weekly increase. Because the step-up is compressed into about a month, the unsettled phase arrives and passes faster than with a weekly pen. If something is not settling, or is bad enough to stop you eating and drinking normally, contact your prescriber rather than waiting it out.

Not more, but differently distributed. The kinds of effect are much the same across this class of medicine. What changes is the shape: injection site reactions come up more often because you inject seven times as often, and the difficult step-up phase is shorter but more concentrated. Which pattern suits someone better is genuinely individual, and a prescriber is better placed to judge it than a comparison table.

Possibly. A change in the sense of taste is listed among the effects reported by up to 1 in 10 people, so it is recognised rather than unusual. It is worth mentioning at your next contact, particularly if it is putting you off eating altogether — appetite suppressed to the point where you are not eating or drinking enough is a reason to speak to your prescriber, not a sign of success.

Yes, and it is worth weighing before you order rather than after. Side effects are the point at which you need to reach someone, and a service that is only a checkout is no use then. A legitimate provider names the people responsible for your care and gives you a way to contact them. If you cannot reach anyone and you are unwell, use NHS 111 or emergency services — waiting for a reply is not a safe plan.

Sources