Symptoms of High B12 Levels: What Your Body Is Telling You
Having high B12 levels in your blood is not usually a big problem. Your body is really good at getting rid of extra B12. But sometimes, high levels can be a sign that something else is going on in your body. Most people do not have any symptoms at all when their B12 is high. Let me walk you through what you need to know.
In this article, you will learn what high B12 levels mean, what symptoms to watch for, what causes them, and what you can do about it. We will keep things simple and clear so you know exactly what to look for.
What Are High B12 Levels?
Normal B12 levels in your blood are usually between 200 and 900 picograms per milliliter (pg/mL). If your levels go above 900 pg/mL, doctors call this high B12 or hypercobalaminemia. Some labs use slightly different numbers, but anything over 950 pg/mL is almost always considered high.
Here is what the numbers mean:
- Normal: 200-900 pg/mL
- Borderline: 900-950 pg/mL
- High: Above 950 pg/mL
B12 is a water-soluble vitamin. This means your body does not store it like fat-soluble vitamins. When you have too much, your kidneys usually filter it out in your pee. This is why having high B12 is pretty rare.
Common Symptoms of High B12 Levels
Most people with high B12 do not feel any symptoms at all. When symptoms do show up, they are often caused by the health problem creating the high B12, not the B12 itself.
Physical Symptoms You Might Notice
Skin Changes
One of the most talked-about symptoms is acne or skin rashes. High doses of B12 can cause red, bumpy skin that looks like acne. This happens because B12 changes how skin bacteria behave. The rash usually shows up on your face, chest, back, and shoulders. It can be itchy and comes on suddenly after starting B12 supplements or injections.
Headaches
Some people get headaches when their B12 levels are very high. These headaches feel like regular tension headaches but might come on more often.
Dizziness
Feeling dizzy or lightheaded can happen with high B12. You might feel unsteady when you stand up or turn your head quickly.
Numbness or Tingling
This sounds strange because low B12 also causes numbness and tingling. But in rare cases, very high B12 from supplements can cause the same feeling in your hands, feet, or face. This usually goes away when you stop taking so much B12.
Digestive Issues
High B12 can upset your stomach. You might feel:
- Sick to your stomach (nausea)
- Not hungry
- Loose stools (diarrhea)
- Upset stomach
These symptoms are more common when you first start taking high-dose B12 supplements.
Heart-Related Symptoms
In some people, too much B12 can affect the heart. Symptoms include:
- Fast heartbeat
- Chest tightness
- Trouble catching your breath
- Feeling your heart race or skip beats
These symptoms are rare and usually happen with very high doses from injections.
Mood and Energy Changes
You might notice:
- Feeling anxious or worried
- Trouble sleeping
- Feeling restless or jittery
- Being more irritable than usual
What Causes High B12 Levels?
High B12 does not just happen on its own. There is always a reason behind it. Let me explain the most common causes.
Taking Too Many Supplements
This is the number one reason people have high B12. Many supplements contain 1,000 to 5,000 micrograms of B12. But you only need about 2.4 micrograms each day. Taking way more than you need can push your blood levels up high.
B12 injections can also cause very high levels. Some people get weekly shots with 1,000 micrograms or more. While these help people with B12 deficiency, they can be too much for someone with normal levels.
Liver Disease
Your liver stores most of the B12 in your body. When your liver is damaged from disease, it releases stored B12 into your bloodstream. This can happen with:
- Hepatitis
- Fatty liver disease
- Cirrhosis
- Liver cancer
The more damaged the liver, the higher the B12 levels can get. Sometimes B12 levels are 2 to 3 times higher than normal.
Kidney Problems
Your kidneys filter out extra B12 from your blood. If your kidneys are not working well, B12 can build up. This happens with:
- Chronic kidney disease
- Kidney failure
- Reduced kidney function from diabetes or high blood pressure
People on dialysis sometimes have higher B12 levels because their kidneys cannot filter properly.
Blood Disorders
Certain blood problems can raise B12 levels. These include:
- Leukemia
- Polycythemia vera
- Other bone marrow disorders
These conditions change how your body makes blood cells and handles B12.
Other Medical Conditions
High B12 can also be linked to:
- Diabetes
- Some types of cancer
- Autoimmune diseases
- Infections
How High B12 Levels Are Diagnosed
Finding out if your B12 is high starts with a simple blood test. Your doctor will order a serum B12 test. You might need to fast for 6 to 8 hours before the test.
What Tests You Might Need
Serum B12 Test
This measures the total amount of B12 in your blood. It is the most common test. Results come back in a few days.
Holotranscobalamin Test
This test measures active B12 that your cells can use. It gives a better picture of how much B12 your body actually has available.
Complete Blood Count
This checks your red blood cells, white blood cells, and platelets. It helps rule out blood disorders.
Liver Function Tests
These check how well your liver is working. If your liver enzymes are high, it might explain high B12.
Kidney Function Tests
These measure how well your kidneys filter waste. Poor kidney function can cause high B12.
When High B12 Levels Are Dangerous
Having high B12 is usually not dangerous by itself. But it can point to serious health problems that need attention.
Short-Term Risks
In the short term, high B12 from supplements or injections can cause:
- Skin rashes that clear up in 2-3 weeks
- Upset stomach that goes away when you stop the supplement
- Mild allergic reactions
These are not life-threatening and go away quickly.
Long-Term Health Concerns
Research shows that having high B12 for a long time might be linked to:
- Higher risk of death in older adults
- Increased cancer risk
- Worse outcomes for people with kidney disease
One study found that for every 135 pg/mL increase in B12, there was a 4% higher risk of death in adults and 6% in seniors. High B12 might also be an early warning sign of cancer, especially in the first year after discovery.
When to See a Doctor Right Away
Call your doctor if you have:
- Severe allergic reactions (trouble breathing, swelling of face or throat)
- Chest pain that does not go away
- Very bad headaches that come on suddenly
- New numbness or weakness
- Severe skin reactions
These could be signs of something serious that needs immediate care.
What to Do If Your B12 Is Too High
The good news is that treating high B12 is usually simple. Here is what you can do.
Stop or Reduce Supplements
If you are taking B12 supplements, the first step is to stop or cut back. Talk to your doctor before making changes. They might suggest:
- Stopping supplements completely for a few months
- Switching to a lower dose
- Taking B12 only once or twice a week instead of daily
Because B12 is water-soluble, your levels will drop fairly quickly once you stop taking extra.
Treat Underlying Conditions
If a health problem is causing high B12, treating that condition is key. This might mean:
- Managing liver disease with medication and lifestyle changes
- Working with a kidney specialist if you have kidney problems
- Getting treatment for blood disorders
- Addressing any infections or autoimmune issues
Monitor Your Levels
Your doctor will want to recheck your B12 levels every 3 to 6 months until they are back to normal. This helps make sure the treatment is working.
Adjust Your Diet
While food rarely causes high B12 on its own, you can eat less of foods rich in B12 if your doctor suggests it. Foods highest in B12 include:
- Clams and shellfish
- Liver
- Beef
- Fish like salmon and trout
- Eggs
- Dairy products
Most people do not need to avoid these foods completely. Just eat them in normal amounts.
Can You Overdose on B12?
True B12 overdose is extremely rare. The National Academy of Medicine has not set an upper limit for B12 because it is so safe. Even taking 1,000 times the daily amount is not usually toxic.
Why B12 Is So Safe
B12 is safe for a few reasons:
- It dissolves in water, so extra amounts leave your body in pee
- Your body only absorbs a small amount at once
- Your kidneys are very good at filtering it out
The Exception: Very High Doses
The main risk comes from getting very high doses through injections over and over. In rare cases, people have had reactions like:
- Severe acne
- Heart palpitations
- Anxiety and panic attacks
- Trouble sleeping
These symptoms usually go away within days or weeks of stopping the injections.
High B12 vs Low B12: What’s the Difference?
It might seem confusing, but high and low B12 can cause some similar symptoms. Here is how to tell them apart.
Symptoms That Overlap
Both high and low B12 can cause:
- Numbness and tingling
- Fatigue
- Headaches
- Trouble concentrating
Key Differences
Low B12 specifically causes:
- Pale or yellow skin
- Sore, red tongue
- Memory problems
- Depression
- Anemia (too few red blood cells)
High B12 specifically causes:
- Acne-like skin rash
- Symptoms from liver or kidney disease
- Often no symptoms at all
The best way to know is through a blood test. Do not try to guess based on symptoms alone.
Special Situations and High B12
Some groups of people need to be extra careful about B12 levels.
Older Adults
As you age, your body changes how it handles B12. Seniors with high B12 have a higher risk of health problems. If you are over 65, talk to your doctor about checking your B12 levels regularly.
People with MTHFR Gene Mutation
If you have an MTHFR gene mutation, you might need methylated B12 to feel your best. But you still need to watch your levels. Taking too much can cause the same problems as regular B12.
Vegans and Vegetarians
Vegans need B12 supplements because plants do not have enough of it. But be careful not to overdo it. Stick to the recommended dose of around 50-100 micrograms per day unless your doctor says otherwise.
People with Kidney Disease
If you have kidney disease, talk to your doctor before taking any B12 supplements. Your kidneys might not filter extra B12 well, which can cause levels to build up.
Myths About High B12 Levels
Let me clear up some common confusion.
Myth 1: More B12 Means More Energy
Many people think taking mega doses of B12 will give them tons of energy. This only works if you are actually deficient. If your levels are normal, extra B12 will not boost your energy. Your body just pees out what it does not need.
Myth 2: You Can’t Have Too Much B12
While B12 is very safe, having high levels can signal health problems. It is not something to ignore, especially if you are not taking supplements.
Myth 3: High B12 Always Causes Symptoms
Most people with high B12 feel totally normal. You could have high levels for months or years without knowing it. This is why regular blood tests are important if you take supplements.
Myth 4: Food Alone Can Cause High B12
It is almost impossible to get too much B12 from food alone. You would have to eat huge amounts of liver or shellfish every day. Supplements and injections are almost always the cause.
How to Keep Your B12 in the Healthy Range
The goal is to have enough B12 without going overboard. Here is how to find that sweet spot.
Get Regular Blood Tests
If you take B12 supplements, check your levels once a year. If you have liver disease, kidney disease, or other health problems, check every 3 to 6 months.
Take the Right Dose
For most adults, 2.4 micrograms per day is enough. If you take a supplement, look for one with 50-250 micrograms. This gives you enough without going too high.
Consider methylated B12 if you have trouble absorbing regular B12. It is easier for your body to use.
Work with Your Doctor
Do not start or stop B12 supplements without talking to your doctor first. They can help you figure out the right dose based on your blood tests and health history.
Watch for Warning Signs
Pay attention to your body. If you notice new skin rashes, digestive issues, or other symptoms after starting B12, tell your doctor.
Balance Your Diet
Eat a mix of B12-rich foods if you can. This is safer than relying only on high-dose supplements. Good choices include:
- Fish twice a week
- Eggs a few times a week
- A serving of meat or poultry most days
- Dairy products daily
For vegans, fortified foods and supplements are important but stick to reasonable doses.
Understanding the Connection Between B12 and Other Health Conditions
High B12 does not happen in a vacuum. It is often connected to other health issues.
Liver Disease and B12
Your liver is like a B12 storage tank. A healthy liver holds enough B12 to last 3-5 years. When liver cells die or get damaged, they dump B12 into your blood. This is why people with hepatitis, fatty liver, or cirrhosis often have high B12.
The B12 level often matches how bad the liver damage is. Very high levels might mean more serious liver problems. The good news is that B12 levels usually go back to normal as the liver heals.
Kidney Function and B12 Filtering
Your kidneys are B12 filters. They take extra B12 out of your blood and put it in your pee. When kidneys do not work well, B12 can build up. People with chronic kidney disease need to be careful with B12 supplements.
Blood Disorders That Affect B12
Some blood problems change how your body handles B12. Leukemia, for example, can increase proteins that carry B12 in your blood. This makes B12 levels look high even though your cells might not be using it well.
Comparing High B12 to Other Vitamin Imbalances
B12 is not the only vitamin that can get out of balance. Let me show you how it compares.
| Vitamin | Risk of Toxicity | Common Symptoms | How Body Handles Extra |
| B12 | Very low | Rare; may include acne, digestive upset | Filtered by kidneys into urine |
| Vitamin D | Moderate | Nausea, weakness, kidney problems | Stored in fat; builds up over time |
| Vitamin A | High | Headaches, vision changes, liver damage | Stored in liver; can be toxic |
| Vitamin C | Very low | Diarrhea, stomach upset | Filtered by kidneys into urine |
| Folate | Very low | May mask B12 deficiency | Filtered by kidneys into urine |
As you can see, water-soluble vitamins like B12 are much safer than fat-soluble ones. But that does not mean you should take unlimited amounts.
Frequently Asked Questions About High B12
Can high B12 cause weight gain?
No, high B12 does not cause weight gain. Some people take B12 for energy and end up eating more, which can lead to weight gain. But the B12 itself does not make you gain weight.
Will high B12 hurt my baby if I’m pregnant?
High B12 during pregnancy is usually safe. But always tell your doctor what supplements you are taking. They will make sure your dose is right for you and your baby.
How long does it take for high B12 to go down?
If you stop taking supplements, your B12 levels will start dropping within a few weeks. It might take 2-3 months to get back to normal. If a health condition is causing high B12, it takes longer and depends on treating that condition.
Can high B12 cause anxiety?
Very high doses of B12, especially from injections, can make some people feel anxious or jittery. This is rare and usually goes away quickly when you stop or reduce the dose.
Is high B12 linked to cancer?
Research shows that unexplained high B12 might be an early sign of some cancers. But B12 does not cause cancer. Instead, certain cancers can raise B12 levels. If your B12 is high without a clear reason, your doctor might want to check for other problems.
Can I take other B vitamins with high B12?
Yes, usually. B vitamins work together in your body. But talk to your doctor first. Some methylated B12 supplements include folate, which is safe and helpful for most people.
Living with High B12: A Practical Approach
If you find out your B12 is high, do not panic. Here is your action plan:
- Talk to your doctor about what might be causing it
- Adjust your supplements based on their advice
- Get follow-up tests to track your levels
- Address any underlying health problems
- Stay aware of symptoms and report new ones
Most cases of high B12 are easy to fix. Just cutting back on supplements brings levels down. The key is working with your healthcare team and staying on top of your health.
Final Thoughts
High B12 levels are not usually something to worry about on their own. Most people have no symptoms at all. But high levels can be a clue that something else is going on in your body, like liver disease, kidney problems, or blood disorders.
If you are taking B12 supplements and your levels are high, talk to your doctor about lowering your dose. If you are not taking supplements and your B12 is high, you need more tests to find out why.
The most important thing is to work with your doctor. They can help you figure out what is causing high B12 and what to do about it. Regular blood tests, the right dose of B12, and paying attention to your body will keep you healthy.
Remember, B12 is an important vitamin that your body needs. The goal is not to avoid it completely. The goal is to have just the right amount – not too little, not too much. With the right care and attention, you can keep your B12 in the healthy range and feel your best.
If you want to learn more about how B12 works in your body, check out the other helpful guides on our site. We are here to help you understand your health and make smart choices.