B vitamins are a set of nutrients that are essential for human life. The B vitamins, or B complex include vitamins B-1, B-2, B-3, B-5, B-6, B-7, B-9 and B-12. Respectively, these vitamins are also called thiamine, riboflavin, niacin, pantothenic acid, pyridoxine, biotin, folic acid and cobalamin. Normally, excess B vitamins are excreted by the kidneys, but high doses of vitamin B supplements can lead to an overdose.
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Overdosing on thiamine, or vitamin B-1, is rare but can cause severe symptoms. Mild symptoms of an overdose include weakness and a headache, the American Pregnancy Association reports. In some cases, high vitamin B-1 levels can cause a rapid, irregular heart beat and low blood pressure. These symptoms can lead to cardiac problems. Some patients will develop a low blood pressure and convulsions.
There are few potential side effects from high doses of riboflavin. The most serious side effects concern an increased rate of allergic reactions in patients taking high doses of riboflavin. Symptoms of allergic reactions include swelling of the face or tongue, hives and difficulty breathing, Drugs.com states. Consult a doctor if you develop these symptoms after taking vitamin B-2. Riboflavin can also cause a harmless yellow-orange discoloration of your urine.
Overdosing on niacin, also called vitamin B-3, can lead to rare side effects. The most apparent symptom of a niacin overdose is a blurring of vision, the American Cancer Society says. This can be a sudden symptom that is disorienting and frightening. You may also experience gastrointestinal symptoms such as nausea, stomach pain and vomiting.
Pantothenic Acid and Biotin Overdose
Pantothenic acid, vitamin B-5, and biotin, vitamin B-7, are necessary for normal metabolism and the breakdown of proteins and carbohydrates. High doses of vitamin B-5 can cause severe diarrhea according to Medline Plus, a service of the National Institutes of Health. However, there are no known toxicities associated with biotin intake.
Toxic levels of pyridoxine have been known to cause a variety of muscular or nerve problems. You may experience burning pains, clumsiness, a loss of muscle coordination and even paralysis, the American Pregnancy Association reports. Vitamin B-6 toxicity can also cause rapid breathing and dyspnea
Folic Acid Overdose
Folic acid, or vitamin B-9, is dangerous when taken in high dosages. Normally, folic acid is given to help keep nerves healthy and ensure a healthy pregnancy. However, in doses greater than 15,000 ug per day, vitamin B-9 can cause damage to your central nervous system, the American Pregnancy Association warns. This may manifest as movement disorders, paralysis, pain or numbness.
Excess intake of cobalamin, or vitamin B-12, may cause some symptoms in patients. You may develop blood clots, itching, diarrhea and serious allergic reaction, Medline Plus says. To avoid these symptoms, take vitamin B-12 as recommended by your doctor.