What is B6 toxicity?

Vitamin B6 toxicity (also called vitamin B6 poisoning) happens when your body reacts to having too much vitamin B6. It usually occurs from taking high doses of vitamin B6 supplements over time, rather than from food. This is sometimes known as 'overdose'.

When too much vitamin B6 builds up in the body, it can accumulate in the blood and damage your nerves. This may lead to a condition called peripheral neuropathy, which causes tingling, burning or numbness, usually in your hands and feet.

Not everyone who takes high doses of vitamin B6 develops toxicity. It isn't clear why it affects some people and not others.

What is vitamin B6?

B6 is an essential vitamin that helps your nervous system function. It is a group of compounds (chemicals) that include many forms, for example pyridoxal, pyridoxine, pyridoxamine and their phosphate forms.

Most people get enough vitamin B6 through their diet.

Read more about vitamin B and your health.

Eating vitamin B6 from food, even in large amounts, will not cause toxicity, poisoning or overdose.

How much vitamin B6 do I need?

How much B6 you need depends on your age and sex. Most people do not need B6 supplements and can get what they need from food. Vitamin B6 can be found in many foods, including:

• meat and chicken
• nuts
• cereals
• bananas

Vitamin B6 supplements come in different forms and doses. Ask your pharmacist, dietitian or doctor if you need them, and if a blood test could help check your levels.

The Australian Dietary Guidelines warn against overdose of B6, which can happen if you take too many vitamin supplements, or foods and drinks with added vitamins.

Here is a guide to how much vitamin B6 you need in your diet:

Children and Adolescents

Adults

What are the symptoms of B6 toxicity?

Taking too much B6 can lead to toxicity and cause nerve damage. The symptoms of nerve damage caused by having too much vitamin B6 include:

• muscle weakness
• numbness
• tingling, burning or 'pins and needles' sensations
• loss of reflexes
• nerve pain

Symptoms often start in your extremities (your fingers and toes). They gradually progress to other parts of your body.

If you experience any of these symptoms while taking B6 supplements or multivitamins, see your doctor or pharmacist.

What causes vitamin B6 toxicity?

Vitamin B6 toxicity can be caused by taking too many supplements. Vitamin B6 supplements are usually safe, but people process vitamin B6 at different speeds. A dose that is safe for one person may be too high for someone else.

The recommended upper limit for vitamin B6 is 50 milligrams per day. Taking B6 supplements for a long period of time, even at a safe dose, can still cause toxicity. This is because pyridoxine can stay in your blood for up to a month, so small daily doses can build up over time.

When should I see my doctor?

You should see your doctor if you are taking B6 supplements or multivitamins containing B6 or its different chemical forms and:

• feel any numbness, tingling or loss of sensation
• have trouble walking or balancing
• feel a loss of coordination
• have a burning feeling or pain

It's important to contact your doctor immediately, as continuing to take vitamin B6 can cause the neuropathy (nerve damage) to progress.

How is B6 toxicity diagnosed?

To diagnose vitamin B6 toxicity, your doctor may check the labels of supplements that you are taking or have previously taken. They will ask you questions about your use of supplements, including supplements for other vitamins, sports drinks or other products.

Your vitamin B6 levels can be tested with a blood or urine test.

Your doctor will ask you questions about your symptoms, and if anything makes them worse or better. They will want to know how long you have had the symptoms.

To diagnose nerve damage, your doctor can carry out a physical examination to check your reflexes and sensation. They may also refer you for nerve conduction studies. They may be able to make the diagnosis based on your history and symptoms alone.

How is B6 toxicity treated?

There is no specific treatment for pyridoxine or B6 toxicity.

The most effective thing to do is to stop taking all supplements that contain B6. Stopping B6 supplements will help to lower your B6 levels. This can be a gradual process as your body works to process the B6 in your system.

The symptoms of nerve damage may not go away immediately. It can take months to years to recover from this damage to your nervous system, and some people never fully recover.

What are the complications of B6 toxicity?

Consuming too much vitamin B6 in the form of pyridoxine can lead to a type of nerve damage called peripheral neuropathy.

Peripheral neuropathy is when your peripheral nerves are damaged. These are the nerves outside the brain and spinal cord.

More advanced symptoms of peripheral neuropathy include:

• loss of balance
• difficulty holding small objects
• trouble walking

This damage is often temporary and may improve when you stop taking B6 supplements.

Read more about peripheral neuropathy.

If you are pregnant or breastfeeding and take too much vitamin B6 in the form of supplements, there is a risk your baby may develop B6 toxicity. Talk to your doctor before taking supplements if you are pregnant or breastfeeding.

If you need a B6 supplement, it is best to speak to your doctor or pharmacist about getting the right dose, and the best way to check your levels during treatment.

Can B6 toxicity be prevented?

You can help prevent vitamin B6 toxicity by carefully reading the labels on your over-the-counter supplements. Check all vitamin and supplement labels to make sure you're not taking too much B6.

It's not always obvious that B6 is included — sometimes it appears as pyridoxine or is combined with another ingredient. For example, many magnesium and zinc supplements, as well as migraine products also contain B6. If you're unsure, ask your pharmacist to check your supplements and advise you on safe use.

Vitamin B6 is also added to many sports or energy drinks, protein and weight loss shakes — check if you're getting extra B6 from the drinks you choose.

Some common names you might see on labels referring to vitamin B6 include:

• pyridoxine hydrochloride
• pyridoxal 5-phosphate
• pyridoxal 5-phosphate monohydrate

The Therapeutic Goods Administration (TGA) requires all products containing more than 10 micrograms of B6 to state this on their label.

Resources and support

Find out more information about B6 toxicity from:

• The Brain Foundation has information on vitamin B6 toxicity.
• Eat for Health lists the recommended amounts of B6 for different ages.

You can call the healthdirect helpline on 1800 022 222 (known as NURSE-ON-CALL in Victoria). A registered nurse is available to speak with you 24 hours a day, 7 days a week.