Possible side effects of taking too much vitamin B6 include abnormal heart rhythms, acne, breast enlargement or soreness, decreased muscle tone and drowsiness, according to Mayo Clinic. Other side effects may include headaches, heartburn, loss of appetite and nausea.
People with blood pressure conditions are advised to exercise caution when taking vitamin B6, as it may trigger low blood pressure, warns Mayo Clinic. It also affects blood sugar levels, and people with diabetes or low blood sugar should also be cautious. Vitamin B6 is also associated with an increase in bleeding, and people with bleeding disorders may require dosage adjustments. Daily doses higher than 200 milligrams may cause seizures or nerve pain.
Women who are pregnant or breast feeding also need to be cautious with vitamin B6 supplements, as it may increase the risk for seizures in infants. High doses and long-term use of vitamin B6 is not safe for pregnant or breastfeeding women, states Mayo Clinic. Other side effects associated with vitamin B6 include rashes, stomach discomfort and sun sensitivity. People without any medical conditions should also avoid long-term usage and high doses of vitamin B6 because it has the potential to cause brain and nerve issues, says WebMD.