Vitamin B6 Toxicity
Taking high doses of vitamin B6 could lead to toxic effects in your body. The classic sign of this problem is peripheral neuropathy (nerve problems in the hands and feet), which can cause numbness, tingling, pricking, and burning. While the nerve problems due to vitamin B6 toxicity are often reversible once the supplement is stopped, very high doses can cause permanent damage.
Vitamin B6 (pyridoxine) is a water-soluble vitamin. Although people tend to think of water-soluble vitamins as being non-toxic, vitamin B6 can actually cause significant toxicity. Although vitamin B6 side effects may sometimes be seen even with normal doses, toxicity usually occurs with high doses.
The classic sign of vitamin B6 toxicity is peripheral neuropathy (nerve problems in the hands and feet). This can cause unusual and unexplained sensations, such as numbness, tingling "pins and needles" feelings, pricking, or burning. These sensations may sometimes affect the area around the mouth as well. If left untreated, the nerve damage can cause difficulty sensing vibrations and sensing the position of the limbs. As you might imagine, this can cause significant coordination problems.
The nerve problems due to vitamin B6 toxicity are often reversible once the vitamin is stopped. However, very high doses (especially if taken chronically) can cause permanent damage.
Vitamin B6 toxicity is due to a very obvious cause -- taking too much vitamin B6. The Recommended Dietary Allowance of vitamin B6 for adults ranges from 1.3 to 2 mg daily, depending on your age and sex (see Vitamin B6 Dosage). The Tolerable Upper Intake Level (the maximum that can be taken from all sources, including the diet, without causing significant toxicity) for adults is 100 mg daily. It is actually fairly easy to exceed the maximum dosage, as many supplements contain 100 mg (or more) of vitamin B6.