- Lifelong WLS multivitamin and at least 1,500 mg calcium a day.
- Dumping after sugar and fat: sweating, palpitations, dizziness.
- Internal hernia in about 1-1.5%.
- Alcohol peaks faster and higher and stays longer.
- The contraceptive pill may be less reliable.
What are the disadvantages of a gastric bypass?
The main structural disadvantage is reduced absorption of nutrients. Without supplements, deficiencies of iron, vitamin B12 and folic acid develop, and to a lesser extent zinc, selenium and vitamins A, E and K. You take a special multivitamin and calcium with vitamin D for life, and have your blood checked regularly.
Other disadvantages come directly from the rerouting. Dumping occurs when sugar or fat reaches the small intestine too fast. An internal hernia can occur when loops of intestine slip through openings in the mesentery. Anti-inflammatory painkillers are forbidden because they can cause an ulcer at the connection.
Gastric bypass and alcohol
After a bypass, alcohol reaches the intestine much faster, where it is absorbed immediately. Blood alcohol peaks faster and higher and stays in the body longer, the Belgian Druglijn explains. Liver specialist Prof. Anja Geerts (Ghent University Hospital) reports that bariatric patients make up 6.5 percent of liver transplants for alcoholic cirrhosis. Surgeon Dr Yves Van Nieuwenhove says doctors increasingly state that alcohol after this operation is not a good idea.
Long-term disadvantages of a gastric bypass
Weight loss holds well for up to about ten years, but some weight can return gradually after five to ten years. Deficiencies can develop years later if vitamins are forgotten. An internal hernia can occur long after surgery, with sudden cramping pain after eating. The risk of kidney stones is higher after a bypass, especially if you had them before.
At the same time the long-term figures for weight are strong: according to WeightWorks, more than 90 percent of patients have lost at least half of their excess weight after ten years.
Advantages and disadvantages side by side
Advantages
| Advantage | Explanation |
|---|---|
| Most experience | most performed operation in the Netherlands |
| Type 2 diabetes | blood sugar often improves within days |
| Less reflux | usually decreases |
| Lasting result | over 90% keep at least half of excess weight off after ten years |
Points of attention
| Point of attention | Explanation |
|---|---|
| Deficiencies | lifelong WLS vitamins and 1,500 mg calcium |
| Dumping | after sugar and fat, 30-45 minutes |
| Internal hernia | about 1-1.5%, even years later |
| Alcohol | faster and higher, more risk of problems |
Cost and insurance (2026)
One disadvantage is financial: some costs remain your own for life.
| Item | Amount or arrangement |
|---|---|
| Operation (with indication) | €385 deductible 2026 |
| Vitamins and calcium | €10-€15 a month, not covered |
| Skin surgery | not always covered |
| Revision with medical reason | basic package |
Gastric bypass disadvantages: key figures
| Feature | Value |
|---|---|
| Internal hernia after bypass | about 1-1.5% |
| Internal hernia after mini bypass | below 0.12% |
| Calcium per day | at least 1,500 mg |
| Dumping lasts | usually no longer than 45 minutes |
| Bariatric patients among alcohol-related liver transplants (Ghent) | 6.5% |
Bypass disadvantages compared with the sleeve
| Disadvantage | Gastric bypass | Gastric sleeve |
|---|---|---|
| Dumping | yes | rarely |
| Internal hernia | about 1-1.5% | not applicable |
| Reflux | usually decreases | can increase |
| Reversible | technically possible | no |
| Alcohol absorption | faster and higher | less pronounced |
Step by step
- Vitamins. Daily WLS multivitamin and calcium, two hours apart.
- Food. Little sugar and fat to prevent dumping.
- Pain relief. Never NSAIDs; paracetamol usually allowed.
- Alcohol. Preferably not; never drink and drive.
- Check-ups. Yearly blood tests, also after five years.
Read next
- Gastric bypass explained — the main page
- Vitamins after a gastric bypass — what to take
- Risks of weight loss surgery — all operations
- Mini gastric bypass disadvantages — comparison
How to limit the disadvantages
Take your vitamins daily and keep attending blood tests, also after the aftercare period. Avoid sugar and fat to prevent dumping, never take NSAIDs, and treat alcohol with great caution. Sudden cramping abdominal pain after eating always needs urgent contact with your centre.
Discuss contraception with your GP before surgery, because the pill may become less reliable. A method that does not depend on the gut, such as an IUD or implant, is often advised.
Frequently asked questions about the disadvantages of a gastric bypass
Having to take vitamins and calcium for life, because fewer nutrients are absorbed. Without supplements, deficiencies of iron, vitamin B12 and folic acid develop, which can still appear years later.
Possible deficiencies, an internal hernia that can occur years later, kidney stones, and gradual regain for some people after five to ten years. Research into long-term mental effects is still limited.
Alcohol reaches your blood faster and at higher levels and stays longer. Doctors at Ghent University Hospital increasingly say alcohol is not a good idea after this operation. Never drink and drive.
A minority does, partly because of the faster absorption and partly because food gives less satisfaction. Discuss any concerns with your team or GP.
Not directly; dumping is mainly triggered by sugar and fat. The sugars in beer and wine can cause strong swings in blood sugar, according to surgeon Yves Van Nieuwenhove.
You receive general anaesthesia via an IV; spinal anaesthesia is not possible. Do not drive for 24 hours afterwards. The anaesthetic risk is small for most people and is discussed beforehand.
Pain and nausea are most common. The most serious early complication, a leak at a staple line, is rare. You eat liquid and puréed food for the first weeks.
The pill can become less reliable because absorption changes. Discuss a method that does not depend on the gut, such as an IUD or implant, with your GP.
Partly. The risk of an internal hernia is lower, below 0.12 percent, but bile reflux is slightly more common. Fat is absorbed less well, so vitamins A, D, E and K need extra attention.
For most people who meet the criteria, yes: lasting weight loss and often improvement of type 2 diabetes and reflux. It requires lifelong discipline around vitamins, food and check-ups.
Call +31 6 38048347 (Mon–Fri 09:00–17:00) or email info@maagverkleining-info.nl. This page is also available in Dutch.
Sources
- Vitalys (Rijnstate): FAQ
- WeightWorks: gastric bypass and mini gastric bypass
- Druglijn: alcohol problems after a gastric bypass
- VRT NWS 2024 and 2026: Prof. Anja Geerts and Dr Yves Van Nieuwenhove (Ghent University Hospital)
- DATO Annual Report 2024, DICA
Search terms leading here: gastric bypass disadvantages, gastric bypass side effects, gastric bypass long term problems, gastric bypass and alcohol.
Author: Gijs Bodenstaff. Last reviewed: September 2026.