Why should folic acid (Folate) be tested along with Vitamin B12?

Folic acid is necessary for human cell development. Folic acid is closely interrelated with Vitamin B12. Folate and B12 work together to produce S-adenosylmethionine (SAMe), a compound involved in immune function and mood. Lack of Folic Acid leads to an increased risk of cardiovascular disease and neural tube defects in women of childbearing age. These risks are attributed to the ability of folic acid to deal with homocysteine* in the body. A deficiency of folic acid or folate may manifest in:

Fatigue
Grey hair
Mouth sores
Tongue swelling
Growth problems
Shortness of breath

Testing for Folate and Vitamin B12 levels is easy and inexpensive.

*homocysteine – Homocysteine is an amino acid produced in the body during the breakdown of protein. High levels of homocysteine in the blood are associated with an increased risk of cardiovascular disease, stroke, and other health problems. It is believed that elevated levels of homocysteine can damage blood vessels, leading to inflammation and other harmful effects. Homocysteine levels can be influenced by factors such as diet, genetics, and lifestyle and can be measured through a blood test.

References: M J Berg, The importance of folic acid, https://pubmed.ncbi.nlm.nih.gov/11252849/ Last accessed 07.06.2021