There are eight types of B vitamins, which are often referred to as the B vitamin complex -- B1, or thiamine; B2, or riboflavin; B3 or niacin; B5, or pantothenic acid; B6; B7, or biotin; B12; and folic acid. All are necessary in adequate amounts to help the body function properly. However, too much of certain kinds of B vitamins can be just as bad for the body. If the symptoms of too much vitamin B appear, seek medical attention.
Upset Stomach
Vitamin B1 is thought to help boost the immune system and protect against the negative effects of stress. Eating a well-balanced diet will provide all of the B1 required, and deficiencies are rare. Thiamine is considered non-toxic, but large doses of vitamin B1 can lead to an upset stomach, according to the University of Maryland Medical Center. Vitamin B5 is used to treat the side effects of many medical conditions, but much more research is needed to determine its effectiveness. Like B1, high doses of B5 can also cause an upset stomach and diarrhea.
Discolored Urine and Diarrhea
Riboflavin deficiencies can occur or even cause many medical conditions, and a doctor may prescribe supplements to help reduce symptoms. While generally considered safe, vitamin B2 can interact with other medications, so a physician should be consulted when supplementing. In some cases, high doses can lead to more frequent urination, the urine turning a yellowish orange color and diarrhea, according to the National Institutes of Health.
Niacin Flush
Niacin also plays a role in sustaining many functions in the body, and a well-rounded diet provides adequate amounts. Deficiencies are rare, and in the U.S., alcoholism is the primary cause for a lack of this vitamin. In high doses, it can be toxic and cause "niacin flush," or a redness accompanied by a burning, tingling sensation in the face and chest, says the University of Maryland Medical Center. Other complications include a worsening of gout, liver damage and stomach ulcers.
Gastrointestinal Problems
Vitamin B6 can be found in foods such as cereal grains, legumes, carrots, spinach, peas, potatoes, milk, cheese, eggs, fish, liver, meat and flour, and according to the Mayo Clinic, mild deficiencies are common. Recommended daily intake varies based on gender, age and overall health, and a physician can advise on when supplementation is needed. Even at low doses, vitamin B6 may not be tolerated well. It can lead to abdominal pain, bloating, nausea, vomiting, headaches, loss of appetite, acne, allergic skin reactions and many other symptoms. B7 or biotin can be used to treat deficiencies during pregnancy and for hair loss, brittle nails, skin rash in infants, diabetes and mild depression. It is considered safe, and there are no known toxic side effects or interactions with other medications when taken as prescribed, states the National Institutes of Health.
Seizures
Adequate folic acid intake is essential throughout life and especially during pregnancy to protect against birth defects. A physician can recommend when supplementation is necessary. Folic acid can be found naturally in many foods, and certain foods are also fortified with it. According to the Office of Dietary Supplements, excessive folic acid intake from foods is not associated with any toxic side effects. When taken in high doses as a supplement by those with seizure disorders, it may possibly trigger a seizure. In addition, taking more than 1,000mcg per day can trigger a deficiency in vitamin B12. If this occurs, supplementation with vitamin B12 is necessary to prevent permanent nerve damage. At this time, the Office of Dietary Supplements states that there are no known toxic side effects from vitamin B12, even in high doses.
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