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Risks - Weight loss surgery

Weight loss surgery carries a risk of complications, some of which can be serious.

Before having surgery, speak to your surgeon about the possible benefits and risks of the procedure.

Blood clots

You'll have treatment to reduce your risk of blood clots after surgery, such as special leg stockings or blood-thinning medicine, but they can sometimes still occur.

Common places for clots to develop are in the lower leg (deep vein thrombosis) or lungs (pulmonary embolism).

Symptoms can include:

  • your lower leg becoming painful, achy and tender
  • swelling, redness or warmth in your lower leg
  • a sharp, stabbing chest pain that may be worse when breathing in
  • shortness of breath or a cough
  • feeling faint or dizzy

Contact your GP or NHS 111 as soon as possible if you think you might have a blood clot.

Wound infection

Sometimes the wounds from your surgery can become infected while they're healing.

Signs of a wound infection can include:

  • pain in or around the wound
  • red, hot and swollen skin
  • pus coming from the wound

Contact your GP or NHS 111 if you think your wound may be infected. They may prescribe a course of antibiotics.

Gastric band slipping out of place

If you have gastric band surgery, there's a small risk that the band could move out of position.

This can cause:

See your GP if you have these symptoms and they don't go away. If your band has moved, you'll need further surgery to put it back in place or remove it.

Leak in the gut

In the days or weeks after a gastric bypass or sleeve gastrectomy, there's a small chance that food could leak out into your tummy.

This can cause a serious infection inside your tummy.

Symptoms of a leak can include:

  • a fever
  • a fast heartbeat
  • tummy pain
  • chills and shivering
  • fast breathing

Call your GP or NHS 111 as soon as possible if you have these symptoms. You may need surgery to repair the leak and antibiotics to treat any infection.

Blocked gut

Sometimes the stomach or small intestine can become narrower or blocked after weight loss surgery.

This can have a number of causes, including food getting stuck, scar tissue in your gut and your gut becoming kinked or twisted.

Symptoms of a blockage can include:

Contact your GP or NHS 111 as soon as possible if you have these symptoms. You may need to have a procedure to widen or clear the blockage using a thin, flexible tube passed down your throat (endoscope).

Cutting food into small chunks, chewing thoroughly and not drinking during meals can help reduce the risk of a blockage.


Weight loss surgery can make it harder for your gut to absorb vitamins and minerals from food, so there's a risk you could become malnourished.

This might not always be obvious, but possible symptoms can include:

Having a balanced diet can help reduce the risk of malnutrition, but most people need to take extra nutritional supplements for life after surgery.

You'll have regular blood tests after surgery to measure your vitamin and mineral levels, so any problems can be picked up and treated.


It's common to develop gallstones in the first year or two after weight loss surgery. These are small, hard stones in the gallbladder that can form if you lose weight quickly.

The main symptom of gallstones is episodes of severe tummy pain that come on suddenly and typically last a few minutes to a few hours.

In a few cases, they can also cause:

  • a high temperature (fever) of 38C (100.4F) or above
  • a fast heartbeat
  • yellowing of the skin and eyes (jaundice)
  • itchy skin
  • chills or shivering
  • confusion

Contact your GP if you have symptoms of gallstones. You may need an operation to remove your gallbladder.

Excess skin

As you lose weight after surgery, you may be left with excess folds and rolls of skin, particularly around your breasts, tummy, hips and limbs.

Surgery, such as a tummy tuck, can be carried out to remove the excess skin, although it's generally considered cosmetic surgery so it isn't always available on the NHS.

Ask your GP if surgery to remove excess skin after weight loss surgery is provided on the NHS where you live.

Risk of dying

Weight loss surgery is a major operation and there is a chance of dying during the procedure or as a result of a serious complication afterwards.

But this is very rare. Recent statistics suggest that only around 1 in 1,400 people who have weight loss surgery in the UK die within a month of the operation.

Page last reviewed: 24 April 2017
Next review due: 24 April 2020