What are the side effects of taking vitamin B6?

Vitamin B-6, also known as pyridoxine, may cause nausea, vomiting, stomach pain, loss of appetite, headaches, tingling and sleepiness when ingested in higher-than-recommended doses, according to WebMD. Long-term use of the vitamin at high doses is possibly unsafe, and it may cause certain brain and nerve problems.

Vitamin B-6 is safe for pregnant women when taken under the supervision of a health care provider, and it can help control morning sickness, states WebMD. Women who breast-feed can take the recommended 2 milligrams per day without any side effects. However, it is considered unsafe when taken in high doses during pregnancy. Side effects on newborns include seizures.