What are the recommended initial investigations for a patient suspected of having folate deficiency?

Recommended initial investigations for suspected folate deficiency:

The UK guideline NG239 primarily focuses on vitamin B12 deficiency and does not provide explicit recommendations for initial investigations specifically for folate deficiency. However, it is standard clinical practice to assess folate status in patients with macrocytic anaemia or symptoms suggestive of megaloblastic anaemia, which can be caused by either vitamin B12 or folate deficiency.

Typically, initial investigations include:

• Full blood count (FBC) to identify macrocytic anaemia.
• Serum folate concentration measurement to assess folate status.
• Serum vitamin B12 (total or active B12) to differentiate from B12 deficiency.

Additional tests such as serum methylmalonic acid (MMA) and plasma homocysteine may be used to clarify ambiguous cases, but these are more specific to vitamin B12 deficiency.

Therefore, for suspected folate deficiency, the initial investigation should include serum folate measurement alongside FBC and vitamin B12 tests to exclude B12 deficiency, as folate deficiency alone is not detailed in the provided guideline.