• Serum folate <3 microgram/L is indicative of folate deficiency (NICE additionally quote intermediate range of 3–4.5 ug/L, however this is not adopted by the laboratory)
• Measure FBC as part of initial investigations of folate deficiency (as per NICE guidelines)
  
  • consider measuring TSH, GGT and liver function test (if not already done)
• Serum folate is reduced in the following conditions (due to increased demand, reduced intake etc):
  
  • normal pregnancy
  • anorexia
  • acute alcohol consumption
  • medications e.g. anticonvulsant therapy. Consult BNF
  • malignancy
  • blood cell disorders
  • dialysis
  • malabsorptive conditions
  • liver disease
  • severe thyroid deficiency
  •  

Precautions

• Low folate may be with low serum cobalamin
  
  • if so, treat with B₁₂ before commencing folic acid 
• If strong clinical suspicion of folate deficiency, despite a normal serum level: 
  
  • exclude cobalamin deficiency
  • measure red cell folate assay (this test is not routinely available – if required contact haematology department)

Specific symptoms for reduced folate (not exhaustive)

• Reduced sense of taste
• Diarrhoea
• Numbness and tingling in the feet and hands
• Muscle weakness
• Depression

Assess for cause

• Diet (most common cause)
• Alcohol consumption
• Gastrointestinal diseases e.g. 
  
  • coeliac disease, inflammatory bowel disease, liver disease, GI surgery
• Pregnancy status
• Exfoliative skin diseases
• Renal dialysis 
• Medications 
• History/symptoms due to haemolytic anaemia

• Dietary sources of folate
  
  • asparagus, broccoli, brown rice, chickpeas, sprouts, peas 
• Follow schedules outlined in BNF
• Renal dialysis patients, follow renal protocols
  
  • note Renavit® contains 1 mg folic acid. Give after dialysis
  • excess folic acid may cause dynamic bone disease
• Transfusion not indicated in haematinic deficiency unless haemodynamic instability
  
  • see Red blood cell transfusion guideline
  • see Chronic anaemia guideline 

• Monitor reticulocyte count and FBC parameters initially
• Monitor serum folate level as dictated by clinical indication
• Note: minimum retest interval for folate for laboratory is 90 days (may not correlate with this guidance)

• Inform GP of:
  
  • cause
  • treatment
  • monitoring required
• If folate deficiency secondary to haemolysis liaise with clinical haematology for follow-up