What are the preparation instructions for a patient undergoing iron studies?

Patient Preparation for Iron Studies

Patients should ideally have blood drawn in the morning after avoiding all iron-containing supplements and foods for at least 24 hours prior to the blood draw. 1

Timing of Blood Collection

• Morning collection is strongly preferred because iron levels exhibit diurnal variation, with highest values typically occurring in the morning 1
• Blood should be drawn between 7 AM and 12 PM when possible to standardize results 1

Dietary and Supplement Restrictions

• Patients must avoid all iron-containing supplements for at least 24 hours before testing 1
• Iron-rich foods should also be avoided for 24 hours prior to blood draw 1
• This includes multivitamins containing iron, iron supplements, and iron-fortified foods 1

Fasting Requirements

Fasting is NOT required for iron studies specifically, but patients should be clearly instructed about this to avoid surreptitious fasting 2, 3

• Many patients mistakenly believe they need to fast for all blood work, with nearly 50% of patients believing fasting is important for every blood test 3
• Surreptitious fasting (fasting without physician instruction) occurs in a substantial proportion of patients and can lead to misinterpretation of concurrent glucose testing 3
• Explicitly tell patients they do NOT need to fast unless other tests being performed require it 2, 3

Transfusion Considerations

Iron studies should be obtained BEFORE any blood transfusion whenever possible 4

• Packed red blood cell transfusion causes a significant rise in serum iron and transferrin saturation that persists for 24-36 hours 4
• If iron studies must be obtained after transfusion, wait at least 24-36 hours, though ideally longer 4
• Diagnosis of iron deficiency based on transferrin saturation <16% may be missed if testing occurs within 24 hours of transfusion 4

Medication Considerations

• Document all medications, particularly those affecting iron absorption or metabolism 1
• Iron-containing medications should be held for 24 hours before testing 1
• Vitamin C supplements can affect iron absorption and should be documented 5

Key Components to Test

A complete iron panel should include 1:

• Serum ferritin (most specific test for iron deficiency) 1, 6
• Transferrin saturation (calculated from serum iron and total iron binding capacity) 1
• Complete blood count with hemoglobin and hematocrit 1

Common Pitfalls to Avoid

• Do not rely on patient self-reporting of fasting status—explicitly document whether fasting was instructed and verify compliance 2, 3
• Do not interpret ferritin in isolation—inflammation can falsely elevate ferritin levels, masking iron deficiency 6
• Do not test within 24 hours of blood transfusion as this will artificially elevate iron parameters 4
• Do not assume patients understand preparation instructions—52% of patients receive no information about proper preparation, and substantial proportions arrive improperly prepared 2

Patient Communication Strategy

Provide written and verbal instructions that explicitly state 2:

• Blood should be drawn in the morning
• Stop all iron supplements and iron-rich foods 24 hours before testing
• Fasting is NOT required (unless other tests necessitate it)
• Take other medications as prescribed unless specifically instructed otherwise
• Avoid blood transfusion before testing if clinically feasible