Vitamin B6 (pyridoxine) is required for the synthesis of the neurotransmitters serotonin and norepinephrine and for myelin formation. Pyridoxine deficiency in adults principally affects the peripheral nerves, skin, mucous membranes, and the circulatory (blood cell) system. In children, the central nervous system (CNS) is also affected. Deficiency can occur in people with uremia, alcoholism, cirrhosis, hyperthyroidism, malabsorption syndromes, and congestive heart failure (CHF), and in those taking certain medications. Mild deficiency of vitamin B6 is common.
Major sources of vitamin B6 include cereal grains, legumes, vegetables (carrots, spinach, peas, and potatoes), milk, cheese, eggs, fish, liver, meat, and flour. Pyridoxine is frequently used in combination with other B vitamins in vitamin B complex formulations.
High homocysteine levels in the blood (hyperhomocysteinemia) have been suggested as being a risk factor for cardiovascular disease. Taking pyridoxine supplements in combination with other B vitamins (folic acid and vitamin B12) has been shown to be effective for lowering homocysteine levels. It is not clear if lowering homocysteine levels results in reduced cardiovascular morbidity and mortality.
Vitamin B6 is also used to treat hereditary sideroblastic anemia, vitamin B6 deficiency, and vitamin B6-dependent seizures in newborns, and to prevent adverse effects in people taking the medication cycloserine. Evidence in support of other uses is inconclusive.
The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.
Adults (18 years and older)
Recommended dietary allowances (RDAs) of vitamin B6 by mouth daily are as follows: for males 19-50 years old, 1.3 milligrams; for males 51 years old and older, 1.7 milligrams; for females 19-50 years old, 1.3 milligrams; and for females 51 years old and older, 1.5 milligrams. Some researchers think the RDA should be increased to the following daily: for women 19-50 years old, 1.5-1.7 milligrams; for pregnant women, 1.9 milligrams; and for lactating women, two milligrams.
Recommended maximum daily intake of vitamin B6 by mouth for adults, pregnant, and lactating women (over 18 years old) is 100 milligrams. A doctor and pharmacist should be consulted for dosing in other conditions.
- For anemia, 25 milligrams of vitamin B6 has been taken by mouth in combination with multivitamins from the second trimester to delivery in pregnant HIV-positive women.
- For anxiety, 50 milligrams of vitamin B6 has been taken by mouth in combination with magnesium daily.
- For birth outcomes, the following doses have been taken by mouth: 20 milligrams daily; three lozenges daily with 6.67 milligrams of pyridoxine in each lozenge; 2.6-20 milligrams of pyridoxine HCl daily; 25 milligrams of pyridoxine HCl daily; and a single dose of 100 milligrams.
- For carpal tunnel syndrome, 200 milligrams of vitamin B6 has been taken by mouth daily for 10-12 weeks.
- For cognitive function, 20 milligrams of vitamin B6 has been taken by mouth daily for 12 weeks.
- For dysmenorrhea, 200 milligrams of vitamin B6 has been taken by mouth daily.
- For gestational diabetes, 100 milligrams of vitamin B6 has been taken by mouth daily for 14 days.
- For high blood pressure, five milligrams of vitamin B6 per kilogram of body weight has been taken by mouth daily for four weeks.
- For McArdle’s disease, 50 milligrams of vitamin B6 has been taken by mouth daily for 10 weeks, without evidence of benefit.
- For pregnancy-induced nausea and vomiting, the following doses have been taken by mouth: 25 milligrams of vitamin B6 every eight hours for 72 hours; 10 milligrams pyridoxine HCl every eight hours for five days; and 100 milligrams of vitamin B6 daily for seven days.
- For premenstrual syndrome, up to 600 milligrams has been taken by mouth; however, 100 milligrams daily has been suggested as the optimal level, due to the potential for side effects at higher doses.
Children (under 18 years old)
The recommended dietary allowances (RDAs) of vitamin B6 (daily) are as follows: for infants 0-6 months old, 0.1 milligrams; for infants 7-12 months old, 0.3 milligrams; for children 1-3 years old, 0.5 milligrams; for children 4-8 years old, 0.6 milligrams; for children 9-13 years old, one milligram; for males 14-18 years old, one milligram; and for females 14-18 years old, 1.2 milligrams.
The recommended maximum daily intakes of vitamin B6 are as follows: for children 1-3 years old, 30 milligrams; for children 4-8 years old, 40 milligrams; for children 9-13 years old, 60 milligrams; and for adult males and females, and pregnant and lactating females 14-18 years old, 80 milligrams.
For hereditary sideroblastic anemia, 2-25 milligrams of vitamin B6, alone or in combination with iron or a multivitamin has been taken by mouth for up to eight weeks.
NB! There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Patients should avoid vitamin B6 products if they are sensitive or allergic to any of their ingredients.
Side Effects and Warnings
Some individuals seem to be particularly sensitive to vitamin B6 and may have problems at lower doses. Overall, pyridoxine is generally considered safe in adults and children when used appropriately at recommended doses.
Arrhythmia (abnormal heart rhythm), skin reactions (such as acne, allergic reactions, and photosensitivity), gastrointestinal effects (such as nausea, vomiting, abdominal pain, loss of appetite, a feeling of a lump in the throat, abdominal discomfort, heartburn, recurrence of ulcerative colitis (in patients with ulcerative colitis)), increased liver function test results (serum aspartate transaminase (AST, SGOT)), neurologic effects (such as headache, paresthesia (an abnormal physical sensation such as prickling, tingling or numbness), somnolence, sedation, and sensory neuropathy), breast soreness or enlargement, persistent bleeding, decreased serum folic acid levels, seizures after large doses, hypotonia (decreased muscle tone or strength), and respiratory distress in infants have been reported.
- Adverse reactions to preservatives in high-dose pyridoxine hydrochloride intravenous injections are possible.
- Vitamin B6 may lower blood pressure. Caution is advised in patients taking agents that lower blood pressure.
- Vitamin B6 may affect blood sugar levels. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Blood glucose levels may need to be monitored by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
- Vitamin B6 may increase the risk of bleeding. Caution is advised in patients with bleeding disorders or those taking drugs that may increase the risk of bleeding. Dosing adjustments may be necessary.
- Use cautiously in patients with cardiovascular or gastrointestinal conditions.
- Use cautiously in patients taking agents for Parkinson’s disease, as pyridoxine enhances the metabolism of levodopa, reducing its antiparkinsonism effects. However, the use of carbidopa and levodopa (Sinemet®) may avoid this interaction, as carbidopa can reduce pyridoxine levels.
- Avoid if allergic or hypersensitive to any ingredient in vitamin B6 products.
- Avoid excessive dosing (doses higher than 200 milligrams daily).
- Avoid high doses during pregnancy or lactation. A special sustained-release multi-ingredient product has been approved by the U.S. Food and Drug Administration (FDA) for use in pregnancy. However, it should not be used long-term, without medical supervision and close monitoring, or in more excessive doses. There is some concern that high-dose maternal pyridoxine can cause neonatal seizures.
Pregnancy and Breastfeeding
Vitamin B6 is likely safe during pregnancy when used orally in doses not exceeding the recommended dietary allowance (RDA). Vitamin B6 is possibly safe when used orally and appropriately in amounts exceeding the recommended dietary allowance. A special sustained-release multi-ingredient product has been approved by the U.S. Food and Drug Administration (FDA) for use in pregnancy. However, it should not be used long-term, without medical supervision and close monitoring, or in more excessive doses. There is some concern that high-dose maternal pyridoxine can cause neonatal seizures.
Vitamin B6 is likely safe during lactation when used orally in doses not exceeding the RDA. There is insufficient reliable information about the safety of pyridoxine when used in higher doses in lactating women. Because most breastfeeding women do not consume the RDA of vitamin B6 in their normal diets and do not provide totally breastfed infants with the RDA of this vitamin, higher doses of vitamin B6 may be recommended, although benefits have not been well proven.