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Vitamin B12 after a urinary diversion | CION Cancer Clinics
A low vitamin B12 level is a known long-term effect of an ileal conduit, a neobladder or any urinary diversion built from the small bowel. The surgeon borrows the stretch of bowel that absorbs B12, and the body's store then runs down slowly over years. This page explains why it happens, what it feels like, how it is checked and replaced, and what to ask at your follow-up visits. CION Cancer Clinics’ surgical oncologists in Hyderabad can talk this through with you.
MI
Medically reviewed by Dr. Mohammed ImaduddinConsultant Surgical Oncologist · MBBS, MS (General Surgery), MCh (Surgical Oncology) · last reviewed September 2026, next review due September 2027
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On this page
- Why can an ileal conduit lower your vitamin B12?
- What does low B12 feel like?
- When does the level usually start to fall?
- What happens when your team tests for it?
- Words you may see on the blood report
- Four things families tell us, and what is actually true
- What this page cannot tell you
- Common questions about B12 after a urinary diversion
The short answer
Why can an ileal conduit lower your vitamin B12?
Yes, a low vitamin B12 level is a known long-term effect of an ileal conduit, and of any urinary diversion built from the small bowel. The surgeon borrows a piece of the last part of the small bowel, and that is the only part of the gut that can absorb B12 from food.
What the surgeon takes and why it matters
In an ileal conduit, a short length of the small bowel (the ileum) is cut out, joined to the tubes from the kidneys, and brought out on the tummy as a stoma. The rest of the bowel is joined back together, so digestion carries on. But the piece used sits close to the end of the small bowel, which is where B12 is picked up. A conduit uses less bowel than a neobladder, so the risk is lower, but it does not disappear.
Why it does not show up straight away
The liver keeps a large store of B12. After the operation that store is used up slowly, so the blood level can look normal for years and then drift down. A normal result in the first year is reassuring but not a reason to stop checking.
This page is about the vitamin, not the operation. If you are still choosing a type of diversion, read the three options first.What to watch for
What does low B12 feel like?
The early signs are vague and easy to blame on age, on the surgery or on the cancer itself. None of them proves a low level. A blood test does.
Tiredness and breathlessness
B12 is needed to make red blood cells. When it runs short, the haemoglobin falls and you tire on stairs or on a short walk. The skin can look pale or slightly yellow.
Numb or tingling feet
B12 protects the covering of the nerves. Pins and needles in the toes, or unsteadiness in the dark, are the signs the doctor worries about most, because nerve damage is slow to reverse.
Tell your team if you notice
- Tingling that climbs from the feet upward
- Dropping things or clumsy hands
- Stumbling when you cannot see your feet
Memory and mood
Forgetfulness, low mood, irritability and poor concentration can all come from a low B12. In an older person these are often put down to age and missed for months.
A sore, smooth tongue
A red, sore tongue, mouth ulcers that keep returning and a changed sense of taste are classic signs, easy to spot at home and worth mentioning at any visit.
Not sure whether this applies to you?
Ask an oncologistOver the years
When does the level usually start to fall?
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Before the operation
Many people in Telangana start with a low or borderline level, often because of a mostly vegetarian diet or long use of acid-reducing tablets or metformin. A test before surgery gives your team a starting point.
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The first year
The liver store covers you. A low reading in this period usually means the level was already low before surgery, or that eating has been poor during recovery and chemotherapy.
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The middle years
This is when the store runs down and the level quietly drops. The person feels well, the scans are clear, and the vitamin is the last thing anyone thinks of. A routine test earns its place here.
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For the rest of your life
The piece of bowel does not grow back and the missing absorption does not return. Whatever checking pattern your team sets, it continues after the cancer follow-up itself has finished.
How it is checked
What happens when your team tests for it?
A blood test
An ordinary sample from the arm, usually taken with the kidney tests at a follow-up visit. Ask for it by name if it is not on the form.
Reading the result
A clearly low level is treated. A borderline level may need a second test, sometimes with a related marker, because the standard B12 test can look normal when the working level is low.
Replacing what is missing
Because the problem is absorption, not diet, your doctor will usually choose injections, or a high-strength tablet that does not need the missing part of the bowel. The choice and the schedule belong to your prescribing doctor.
Checking it worked
A repeat blood test after replacement shows whether the level has come up. If nerve symptoms had started, they are reviewed separately, because they recover more slowly than the blood count.
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On your report
Words you may see on the blood report
- Cobalamin
- Another name for vitamin B12. Cyanocobalamin and methylcobalamin are the two common forms used in injections and tablets in India.
- Terminal ileum
- The last stretch of the small bowel, where B12 is absorbed. It is the part most often borrowed for a diversion.
- Macrocytic
- Red blood cells that are larger than normal. It is an early clue to low B12 that can appear on a routine blood count before the level itself is tested.
- Methylmalonic acid
- A second test used when the B12 result is borderline. A high value means the body is short of usable B12 even if the main test looks acceptable.
Commonly believed
Four things families tell us, and what is actually true
"He eats well, so he cannot be short of a vitamin."
After a diversion the problem is not what goes in, it is what the bowel can take up. Eggs, milk, curd and meat still matter, but they cannot make a missing piece of bowel absorb again.
"Only vegetarians get low B12."
A vegetarian diet makes it more likely, and much of Telangana starts with a lower level for that reason. But after this operation the cause is the surgery, and a person who eats meat every day can still run short.
"An ordinary multivitamin from the chemist will cover it."
Most multivitamins carry a small amount of B12 that relies on normal absorption. Your doctor may choose injections or a much stronger tablet, and will set the form and the schedule. Do not swap or stop what is prescribed on your own.
"Once the level is back to normal, it is finished."
The bowel does not regrow, so the level will drift down again if replacement stops. Most people need it for life, in whatever pattern their doctor sets, alongside their kidney checks.
Being straight with you
What this page cannot tell you
This page cannot tell you whether your own level is low. Only a blood test can. The symptoms above are shared with many other causes, from chemotherapy to thyroid problems to poor sleep.
It cannot set your schedule
How often you are tested, and how B12 is replaced, depends on how much bowel was used, how you eat, what other tablets you take and what your kidneys are doing. Two people with the same operation can be on different plans. Ask your team to write yours down and to say who owns it once the cancer follow-up ends.
Who this matters for most
The risk is higher after a neobladder or a continent pouch, because more bowel is used, and in anyone who was borderline before surgery, is older, takes long-term metformin or acid-reducing tablets, or whose diet has narrowed since the operation.
What to ask at the next visit
Ask whether B12 was tested before surgery, when it was last checked, and whether folate and a full blood count were done with it. If you are being treated, ask what to do if a dose is missed.
If you have numbness that is spreading or you are stumbling, do not wait for the next routine visit. Call the helpline and ask for an earlier appointment.Questions we are asked
Common questions about B12 after a urinary diversion
My father had his conduit years ago and nobody has tested B12. Is that a problem?
Raise it at the next visit rather than worrying at home. The liver store lasts a long time, so a first test now is still useful. Ask for B12, folate and a full blood count together. If the result is low, replacement works whenever it is started, though nerve symptoms take longer to settle.
Are injections better than tablets after this operation?
Injections bypass the bowel altogether, which is why they are often chosen when the absorbing part has been used. Very high-strength tablets can also work for some people, because a small amount is absorbed without the usual route. Your prescribing doctor chooses on the basis of your level and your symptoms.
Can I just eat more eggs, milk and meat instead?
These foods are the main sources of B12 and are still worth eating. But the shortfall after a diversion comes from absorption, not intake, so diet alone may not be enough. Treat the blood test as the judge, not the menu.
Is the risk the same with a neobladder?
It is usually higher, because a neobladder needs a longer piece of bowel than a conduit. Anyone with a neobladder or a continent pouch should expect B12 to be part of their long-term blood checks for life.
Will low B12 affect my cancer treatment?
It can add to tiredness and a low haemoglobin during chemotherapy, and can worsen numbness from some chemotherapy drugs. Correcting it does not treat the cancer, but it can make treatment easier to get through. Tell your medical oncologist if you are on replacement.
I take metformin for diabetes. Does that matter?
Yes. Metformin lowers B12 absorption on its own, and so do long courses of acid-reducing tablets. With a diversion on top, the level can fall sooner. Do not stop either medicine. Tell the doctor who checks your B12 that you take them, so the testing is planned with that in mind.
Can the nerve damage be reversed?
Often, if it is caught early and replacement is started. Tingling and unsteadiness improve over months rather than weeks. Damage that has been there a long time may only partly recover, which is why testing before symptoms appear matters.
Is the test covered under Aarogyasri or insurance?
Follow-up blood tests after cancer surgery are often included under Aarogyasri, CGHS, ECHS and EHS, and most cashless insurers cover them as part of the treatment plan. Cover for long-term replacement varies. Call the helpline with your card details and we will check before you travel.
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Sources
- NHS — Vitamin B12 or folate deficiency
- Cancer Research UK — Surgery for bladder cancer
- Macmillan Cancer Support — Bladder cancer
- National Cancer Institute — Bladder Cancer Treatment (PDQ) - Patient Version
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
Metabolic Problems After Bowel-Based DiversionThe other blood changes that come from using bowel to carry urineKidney Function After Urinary DiversionThe tests that are usually done at the same visitFollow-Up After Radical CystectomyWhere B12 checks fit into the long-term planUrinary Diversion: The Three OptionsHow much bowel each option usesEating and Bowel Function After CystectomyGetting enough of the right foods after the operation
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Not sure whether your B12 has ever been checked?
Send us the last blood report or call the helpline. A CION oncologist will look at what has been tested and tell you what to ask for next. One helpline serves every centre.