Having too much B12 in your blood is usually not dangerous, but it can be a sign of something more serious going on in your body. Most healthy people don’t need to worry about high B12 levels because the body gets rid of extra B12 through your pee. But when B12 levels stay high without taking supplements, it might mean your liver, kidneys, or blood cells need attention from a doctor.
In this article, you’ll learn what high B12 levels mean, what causes them, the signs to watch for, and what steps you can take to get your levels back to normal.
Understanding B12 and Normal Levels
Vitamin B12 is a helper vitamin that keeps your body running smoothly. It helps make red blood cells, protects your nerves, and keeps your brain sharp.
Your body stores B12 mainly in your liver. This storage is so good that a healthy person can go for years without needing more B12.
What Are Normal B12 Levels?
Normal B12 levels in your blood are between 160 and 950 picograms per milliliter. Doctors consider levels above 950 pg/mL to be high.
When your levels go above 1,000 pg/mL without taking supplements, doctors want to figure out why. Very high levels can sometimes point to health problems that need checking.
What Causes High B12 Levels?
High B12 can happen for many reasons. Some are simple fixes, while others need a doctor’s care.
Taking Too Many Supplements
The most common reason for high B12 is taking too much through pills or shots. Many people take B12 supplements to fix a shortage, but sometimes they take more than needed.
B12 shots can push levels very high very fast. One study found that someone who got 15 milligrams of B12 shots over a few weeks started having symptoms.
Taking 1,000 to 2,000 micrograms of B12 daily can raise your levels, though most people won’t notice any problems.
Liver Problems
Your liver stores most of your body’s B12. When the liver gets damaged, it can leak B12 into your blood.
Liver diseases that can raise B12 include:
- Hepatitis (liver swelling)
- Cirrhosis (liver scarring)
- Liver cancer
- Fatty liver disease
Research shows that people with severe liver disease often have B12 levels 2 to 3 times higher than normal.
Kidney Disease
Your kidneys help filter extra B12 from your blood. When kidneys don’t work well, B12 can build up.
People with advanced kidney disease are more likely to have high B12 levels. This is especially true for those not yet on dialysis.
Blood Disorders
Certain blood problems can make B12 levels jump. These include:
- Chronic myelogenous leukemia
- Polycythemia vera
- Other bone marrow cancers
These conditions make extra proteins that hold onto B12, keeping it in your blood instead of letting it leave your body.
Some Types of Cancer
High B12 can be a warning sign of cancer. Research found that people with B12 levels above 1,355 pg/mL had a higher chance of getting diagnosed with cancer within one year.
Cancers linked to high B12 include:
- Liver cancer
- Lung cancer
- Pancreatic cancer
- Breast cancer
- Colon cancer
The cancer itself doesn’t cause high B12. Instead, the body’s reaction to cancer changes how it handles B12.
Eating Too Many B12-Rich Foods
It’s hard but not impossible to get too much B12 from food alone. Foods highest in B12 include:
- Liver and organ meats
- Clams and shellfish
- Fish like salmon and tuna
- Red meat
- Eggs
- Dairy products
People who eat large amounts of these foods daily, especially if they also take B12 supplements or drink energy drinks with B12, might see their levels rise.
What Are the Symptoms of High B12?
Most people with high B12 feel totally fine. The body is good at getting rid of extra B12, so symptoms are rare.
When symptoms do happen, they usually come from B12 shots rather than pills. Common signs include:
Skin Changes
Some people get acne or a rash that looks like rosacea. Their skin might turn red or feel flushed. These skin problems usually go away once B12 levels drop.
Stomach Problems
High B12 can upset your stomach. You might feel:
- Sick to your stomach
- Loss of appetite
- Diarrhea
- Mild cramps
Nervous System Signs
In rare cases, very high B12 can cause:
- Tingling in hands and feet
- Muscle twitches
- Headaches
- Dizziness
- Feeling restless or anxious
Heart-Related Symptoms
B12 shots can sometimes cause:
- Fast heartbeat
- Heart palpitations
- Irregular heartbeat
- Low potassium levels
These are more serious and need quick medical attention.
Sleep Problems
Some people report trouble sleeping when their B12 levels get above 700 pg/mL. This usually gets better when levels come down.
When High B12 Is Dangerous
Having high B12 isn’t toxic like some vitamins can be. But it can be a red flag for serious health problems.
Links to Early Death
Research shows that very high B12 levels in older adults are linked to a higher risk of dying from any cause. One study found that for every 135 pg/mL increase in B12, there was a 4% higher risk of death in the general population and a 6% higher risk in older adults.
Connection to Cancer
Multiple studies show a link between high B12 and cancer risk. One large study found that men who took very high doses of B12 (23 times the daily amount) for 10 years had a 30 to 40% higher risk of lung cancer if they smoked.
But remember: correlation doesn’t mean causation. High B12 might be a sign that cancer is already there, not a cause of cancer.
Heart Disease Concerns
Some research suggests high B12 levels might increase the risk of heart problems in people with diabetes. More studies are needed to understand this connection better.
How Doctors Test for High B12
If your doctor suspects high B12, they’ll order blood tests.
Serum B12 Test
This basic test measures total B12 in your blood. It’s the first test doctors use. Results above 950 pg/mL are considered high.
Additional Tests
If your B12 is high, your doctor might order:
Holotranscobalamin Test: This measures the active form of B12 that your cells can actually use.
Methylmalonic Acid (MMA) Test: High MMA means your body isn’t using B12 properly, even if blood levels look high.
Homocysteine Test: High homocysteine along with high B12 can signal that B12 isn’t working right in your body.
Complete Blood Count: This checks for blood disorders.
Liver Function Tests: These look for liver problems.
Kidney Function Tests: These check how well your kidneys are working.
How to Lower High B12 Levels
The way to lower B12 depends on why it’s high in the first place.
Stop Taking Supplements
If you’re taking B12 pills or getting shots, your doctor might tell you to stop or cut back. Most people see their levels drop within a few weeks to months.
If you take a multivitamin, check the label. Some have over 1,000% of the daily B12 amount you need.
Treat Underlying Health Problems
When high B12 comes from liver disease, kidney problems, or blood disorders, treating those conditions usually brings B12 back to normal.
This might involve:
- Medicine for liver or kidney disease
- Treatment for blood disorders
- Cancer treatment if needed
Change Your Diet
If you eat lots of B12-rich foods, try cutting back on:
- Organ meats like liver
- Shellfish and fish
- Red meat
- Fortified breakfast cereals
- Energy drinks with added B12
You don’t need to avoid these foods completely. Just eat them less often.
Stay Hydrated
Drinking plenty of water helps your kidneys flush out extra B12. Aim for 8 glasses of water daily.
Avoid energy drinks and sports drinks that have added vitamins. Plain water works best.
Regular Monitoring
Your doctor will want to check your B12 levels every 3 to 6 months until they’re back to normal. This helps make sure treatment is working and catches any problems early.
Special Considerations for Methylated B12
Methylated B12 (methylcobalamin) is the active form your body can use right away. Many people take it because it doesn’t need to be converted first.
People with MTHFR gene mutations especially benefit from methylated forms because their bodies struggle to convert regular B12.
However, methylated B12 can still cause high levels if you take too much. The same caution applies as with any other B12 form.
If you’re taking methylated B12 supplements, work with your doctor to find the right dose. Learn more about how to take methylated B12 for maximum absorption.
Understanding the Difference: High B12 vs. B12 Deficiency
It’s important not to confuse high B12 levels with B12 deficiency. These are very different problems.
Signs of B12 Deficiency
Low B12 causes:
- Extreme tiredness
- Weakness
- Pale skin
- Shortness of breath
- Tingling in hands and feet
- Memory problems
- Depression
Learn more about B12 deficiency symptoms here.
The Folate Trap
Sometimes people have high B12 in their blood but their cells can’t use it. This happens when there’s not enough folate (vitamin B9) or when certain enzymes don’t work right.
These people might have symptoms of B12 deficiency even though their blood tests show high B12. This is why doctors check other markers like MMA and homocysteine.
Who Should Worry About High B12?
Not everyone with high B12 needs to worry. You should talk to your doctor if:
- Your B12 is above 1,000 pg/mL without taking supplements
- Your levels keep rising over time
- You have unexplained symptoms like weight loss, fatigue, or stomach pain
- You have a history of liver disease, kidney disease, or blood disorders
- You’re taking high-dose B12 therapy
Most healthy people taking normal amounts of B12 supplements (under 100 micrograms daily) don’t need to worry about their levels getting too high.
Can You Have Too Much of the Right Thing?
B12 is essential for good health, but like anything, balance matters. The body needs about 2.4 micrograms of B12 daily for adults. Pregnant women need 2.6 micrograms, and women who are breastfeeding need 2.8 micrograms.
Taking way more than this amount isn’t necessary for most people. While B12 is very safe, taking mega-doses doesn’t make you healthier if your levels are already normal.
Think of it like watering a plant. A plant needs water to grow, but drowning it in water doesn’t make it grow faster or better.
When to See a Doctor
Make an appointment with your doctor if:
- Blood tests show B12 levels above 950 pg/mL
- You have unexplained symptoms
- You’re taking B12 supplements and aren’t sure if the dose is right
- You have risk factors like liver disease or kidney problems
- Your levels have been rising over several tests
Your doctor can figure out why your B12 is high and create a plan to fix it.
The Role of Methylated B12 for Different Conditions
While high B12 can be a concern, many people actually need B12 supplements for legitimate health reasons:
- Vegans and vegetarians who don’t get B12 from animal foods
- People with MTHFR gene mutations
- Those with nerve health concerns
- Older adults who absorb B12 poorly
- People recovering from fatigue and low energy
The key is finding the right dose for your individual needs. Check out our methylated B12 dosage guide for more information.
Comparing Forms of B12
Different forms of B12 have different properties:
| Form | Absorption | Best For | Notes |
| Methylcobalamin | Good | MTHFR mutations, nerve health | Active form, ready to use |
| Cyanocobalamin | Very good | General supplementation | Needs conversion in body |
| Adenosylcobalamin | Good | Energy production, mitochondrial health | Works in cell mitochondria |
| Hydroxocobalamin | Excellent | Injections, cyanide toxicity | Longer-lasting in body |
Learn more about the difference between methylcobalamin and cyanocobalamin.
Preventing High B12 Levels
Prevention is easier than treatment. Here’s how to keep B12 in the healthy range:
Take Only What You Need
Follow the recommended daily amount unless your doctor prescribes more. Most adults only need 2.4 micrograms daily.
Check Your Supplements
Read labels on all your vitamins and supplements. Add up the total B12 you’re getting each day. Many multivitamins contain 100% or more of the daily value.
Get Regular Blood Tests
If you take B12 supplements or have risk factors for high B12, ask your doctor to check your levels once or twice a year.
Work With Your Doctor
Don’t guess about the right dose. Your doctor can test your levels and tell you exactly how much B12 you need.
Consider Methylated Forms
For some people, methylated B12 works better and may require smaller doses. Talk to your doctor about whether this form is right for you.
Living With High B12 Levels
If you’ve been told your B12 is too high, don’t panic. In most cases, it’s easy to fix.
Stay Calm
High B12 rarely causes immediate harm. Your body has time to adjust as you work with your doctor to find the cause.
Follow Up
Keep all your doctor appointments and get recommended tests. This helps catch any underlying problems early.
Track Your Symptoms
Write down any symptoms you notice. This information helps your doctor figure out what’s going on.
Make Gradual Changes
Don’t make drastic changes to your diet or supplements without talking to your doctor first. Slow, steady adjustments work best.
Common Myths About High B12
Let’s clear up some confusion:
Myth: High B12 always means you’re taking too many supplements. Truth: Liver disease, kidney problems, and blood disorders can all raise B12 without supplements.
Myth: High B12 will cause serious side effects. Truth: Most people with high B12 feel fine. Serious symptoms are rare.
Myth: You should stop eating all B12-rich foods. Truth: You still need some B12 from food. Just don’t overdo it.
Myth: All B12 is the same. Truth: Different forms like methylcobalamin work differently than cyanocobalamin.
Questions to Ask Your Doctor
When discussing high B12 with your doctor, ask:
- What caused my B12 to get so high?
- Do I need more tests to check my liver, kidneys, or blood?
- Should I stop taking my B12 supplement?
- How often should my levels be checked?
- Are there any signs I should watch for?
- Could this be related to other health problems?
Final Thoughts
High B12 levels aren’t usually dangerous by themselves, but they’re worth paying attention to. Most of the time, high B12 comes from taking too many supplements and is easy to fix.
The real concern is when high B12 points to problems with your liver, kidneys, or blood. That’s why it’s important to work with your doctor to figure out the cause.
If you’re taking B12 supplements, make sure you’re taking the right amount for your needs. Consider methylated B12 from a trusted source if you have trouble absorbing regular B12.
Remember: B12 is vital for good health. The goal isn’t to avoid it but to keep your levels in the healthy range. With proper monitoring and care, most people can maintain perfect B12 balance.
Your body knows what it needs. Listen to it, work with your doctor, and you’ll find the right balance for your health.