High blood folate levels do not cause problems but may indicate low vitamin B-12 levels, according to WebMD. A 2011 study conducted by the National Institutes of Health suggests that high folate consumption in healthy individuals does not negatively impact B-12 levels or cause anemia, states the NIH News. However, prior research indicates that high folate levels could adversely affect the elderly.
People with cancer, seizure disorders, stomach problems, lung disorders and nervous system disorders should discuss using folate with a medical professional, according to Mayo Clinic. In most cases, people should not use folate supplements after heart surgery or if they take anti-cancer agents, unless their doctor prescribes them.
Folate also can cause low blood sugar and low blood pressure, notes Mayo Clinic. People shouldn't combine folic acid supplements with aspirin, and they should avoid using dosages beyond the recommended daily maximum of 1,000 micrograms without medical supervision.
Folate may cause a wide variety of side effects, which include narrowed blood vessels that lead to blood flow problems, flushing, hives or redness of the skin, hair loss and weight changes, Mayo Clinic reports. Women taking folate late in their pregnancy may increase the risk of asthma in their child. Folate may also increase the risk of cancer or seizure frequency. Other possible side effects include nausea, a bitter taste, bloating, breathing difficulty and lung muscle spasms. People also may report sleep problems, vivid dreaming, psychotic behavior and impaired judgement.