Vitamin B6, specifically in the form of pyridoxal 5'-phosphate (the active coenzyme form), has scientific validation for its use in the management of nausea and vomiting, particularly in pregnancy (commonly referred to as morning sickness). Multiple randomized controlled trials and meta-analyses have demonstrated that Vitamin B6 supplementation can reduce the severity of nausea and, to a lesser extent, vomiting in pregnant women. The mechanism is not fully understood, but it is thought to involve modulation of neurotransmitter synthesis, including serotonin and dopamine, which play roles in the emetic (vomiting) pathway.

Clinical guidelines in countries such as the United States and Canada recommend Vitamin B6 as a first-line therapy for mild to moderate nausea and vomiting in pregnancy, either alone or in combination with doxylamine. The typical dosage studied is 10–25 mg, three times daily. The evidence is strongest in the context of pregnancy; for other causes of nausea and vomiting (such as chemotherapy-induced or postoperative nausea), the evidence is much weaker or lacking.

In summary, the use of Vitamin B6 for nausea and vomiting in pregnancy is supported by scientific studies and is recommended in clinical practice guidelines. Its use outside of pregnancy for this indication is not well supported by evidence.