Translations:B vitamins/16/en

Vitamin	Tolerable Upper Intake Level (UL)	Harmful effects
Vitamin B1	None	No known toxicity from oral intake. There are some reports of anaphylaxis caused by high-dose thiamin injections into the vein or muscle. However, the doses were greater than the quantity humans can physically absorb from oral intake.
Vitamin B2	None	No evidence of toxicity based on limited human and animal studies. The only evidence of adverse effects associated with riboflavin comes from in vitro studies showing the production of reactive oxygen species (free radicals) when riboflavin was exposed to intense visible and UV light.
Vitamin B3	US UL = 35 mg as a dietary supplement	Intake of 3000 mg/day of nicotinamide and 1500 mg/day of nicotinic acid are associated with nausea, vomiting, and signs and symptoms of liver toxicity. Other effects may include glucose intolerance, and (reversible) ocular effects. Additionally, the nicotinic acid form may cause vasodilatory effects, also known as flushing, including redness of the skin, often accompanied by an itching, tingling, or mild burning sensation, which is also often accompanied by pruritus, headaches, and increased intracranial blood flow, and occasionally accompanied by pain. Medical practitioners prescribe recommended doses up to 2000 mg per day of niacin in either immediate-release or slow-release formats, to lower plasma triglycerides and low-density lipiprotein cholesterol.
Vitamin B5	None	No toxicity known.
Vitamin B6	US UL = 100 mg/day; EU UL = 25 mg/day	See Megavitamin-B6 syndrome for more information.
Vitamin B7	None	No toxicity known.
Folate	1 mg/day	Masks B12 deficiency, which can lead to permanent neurological damage.
Vitamin B12	None established	Skin and spinal lesions. Acne-like rash [causality is not conclusively established].