What is Vitamin B6 Toxicity?
Vitamin B6 is a nutrient that your body needs. This vitamin exists in different forms, with the most common one being pyridoxine, which is found in store-bought vitamin supplements. Vitamin B6 takes part in numerous bodily processes such as helping to create neurotransmitters, processing amino acids and glucose (sugar), managing fats in the body, producing hemoglobin (a blood component), and controlling gene activity.
In the United States, people generally get about 1.9 milligrams of Vitamin B6 in their meals every day. Eating foods rich in pyridoxine will not lead to an excess of Vitamin B6 in your body. Overdose cases have only been reported in situations where someone has taken high doses of vitamin supplements or had an accidental administration of the vitamin.
What Causes Vitamin B6 Toxicity?
Vitamin B6 toxicity, or having too much vitamin B6 in your body, usually happens when people take too much of this vitamin, either because a doctor prescribes high doses or when people take over-the-counter supplements on their own. The amount of vitamin B6 that we get from food every day is not enough to cause toxicity. For example, in the United States, the average daily intake is about 1.9 mg.
Sometimes, people take vitamin B6 with another medication called isoniazid, usually in doses of 10 to 25 mg a day. When people have too much vitamin B6, they can experience nerve-related symptoms which can include feelings like pin-pricks in their arms and legs. In serious cases, they might find it hard to walk. This nerve damage usually happens when people take more than 1000 mg of vitamin B6 a day.
There have been a few cases where people developed nerve damage after taking less than 500 mg of vitamin B6 a day for several months. But, no studies have shown nerve damage in people who took less than 200 mg of vitamin B6 a day.
It’s also worth mentioning that a very rare cause of vitamin B6 toxicity is a condition called hypophosphatasia.
Risk Factors and Frequency for Vitamin B6 Toxicity
Vitamin B6, also known as Pyridoxine, is often used as a supplement to treat a wide range of health conditions. This includes cases of severe morning sickness known as hyperemesis gravidarum, depression, premenstrual syndrome, and even carpal tunnel syndrome. It’s also used as an antidote in high doses for seizures caused by an overdose of the drug isoniazid. However, the effectiveness of using Vitamin B6 for these health benefits is a topic of debate.
Despite its potential benefits, taking too much Vitamin B6 can actually be harmful. Most of the time, people take too much Vitamin B6 through over-the-counter supplements without realizing the possible risks. A reported case study highlighted a patient who had been taking 50 times the recommended daily doses of Vitamin B6 supplements, which led to peripheral neuropathy, a condition that damages your peripheral nerves and causes weakness, numbness, and pain.
- In 2017, the U.S. poison center recorded 566 cases where Pyridoxine was used as an antidote in therapeutic doses.
- There were 377 reported cases of exposure to Pyridoxine.
- Out of these cases, eight had minor to moderate clinical effects.
- Fortunately, no serious outcomes or deaths were reported due to Pyridoxine exposure.
Signs and Symptoms of Vitamin B6 Toxicity
Doctors rely on a patient’s medical history and physical examinations to identify cases of vitamin B6 toxicity. Most people experiencing vitamin B6 toxicity will have symptoms related to nerve damage, including numbness or pain in arms and legs. It’s important for doctors to understand all the medications and supplements a patient is taking, as vitamin B6 toxicity often happens because of overdosing on supplements. Since supplement bottles can have a range of B6 amounts, a good practice is to bring the actual bottles to the doctor. This helps provide an accurate understanding of the specific vitamin dosage.
The doctor’s physical examination will involve a detailed review of your neurological health. This includes checks on feelings of touch, motor activities, balance, reflexes, the functioning of the cranial nerves, and muscle strength. Patients generally show changes affecting both sides of the body. But if you’ve previously had an injury or neurological damage to a limb, it could affect one side more.
Testing for Vitamin B6 Toxicity
In simple terms, if the level of pyridoxine (a form of vitamin B6) in the blood is less than 30 mcg/L, it is usually considered low. If someone shows signs or symptoms of nerve damage diseases, they should be referred to a specialist, like a neurologist, who can perform specific tests known as nerve conduction velocity studies.
The process of diagnosing this condition usually starts with the patient talking about signs and symptoms of peripheral sensory neuropathy. This refers to a condition where the nerves that carry messages to and from the brain and spinal cord from and to the rest of the body, don’t work properly. The purpose of this deep investigation is not only to confirm the presence of this disease but also to exclude other potential causes of nerve damage.
Treatment Options for Vitamin B6 Toxicity
If you take too much pyridoxine, also known as B6, there isn’t a specific treatment or antidote. The best approach is to stop taking the supplement as soon as the excessive intake is diagnosed. The rest of the treatment is focused on managing the symptoms and providing supportive care if any effects persist or can’t be reversed. Physical therapy may be recommended if it’s suitable.
When prescribing B6, the person’s age should be considered. Here are the daily recommended amounts depending on age:
- Children should get 0.5 to 1 mg
- Young adults should get 1.3 mg
- Men over 50 should get 1.7 mg
- Women over 50 should get 0.5 mg
What else can Vitamin B6 Toxicity be?
If someone is showing signs of having too much vitamin B6 in their body, it can often be mistaken for other health problems. It could simply be an excess or lack of different vitamins, such as vitamin B12, because the symptoms are alike. It’s also necessary to consider diseases and conditions that affect the nerves in your arms and legs, which is called peripheral neuropathy.
Here are some things that could cause these symptoms:
- Diabetes
- Autoimmune diseases like lupus
- Ongoing liver disease
- Advanced liver disease
- HIV/AIDS
- Underactive thyroid (hypothyroidism)
- Lyme disease
- Lymphoma (a type of cancer)
- Monoclonal gammopathy (a possible sign of blood diseases)
- Syphilis
- Porphyria (a group of rare genetic disorders)
- Specific medicines
- Harmful substances including heavy metals, alcohol, organophosphates (a type of pesticide), and other vitamin toxicity.
Understanding a person’s history of exposure to these potential causes and tracking the progress of the symptoms over time can help doctors tell these conditions apart. Additional lab tests and studies that measure how fast electrical signals travel along your nerves can also assist in finding the accurate cause.
What to expect with Vitamin B6 Toxicity
The outlook is generally positive, with symptoms getting better or even disappearing once the overuse of pyridoxine (vitamin B6) is identified and stopped. However, nerve damage due to extremely high exposure can cause lasting disability or even death. Neurological problems improve after stopping the vitamin B supplementation and typically get better within six months. However, some patients might not recover fully.
Possible Complications When Diagnosed with Vitamin B6 Toxicity
With long-term use of dosages above 250 mg/day, patients usually start to feel symptoms like nerve damage symptoms, skin conditions, sensitivity to light, feelings of being off-balance, abnormal touch sensations, and even nausea. These are all part of what doctors call ‘peripheral neuropathy’. Other possible health risks could include uncoordinated movements (ataxia) and uncomfortable or painful feelings in the skin (dysesthesias).
Preventing Vitamin B6 Toxicity
It’s important for patients to understand about the vitamins and minerals they get from what they eat every day. Advice should be given to those who are considering taking extra amounts of a vitamin called pyridoxine, and they should also be aware of the risks associated with taking high doses. When doctors use pyridoxine as a treatment, they usually give it in smaller amounts.
