iron deficiency anemia; injection site pain; good and bad days; mild headache; Pain in arm; This spontaneous case was reported by a physician and describes the occurrence of IRON DEFICIENCY ANAEMIA (iron deficiency anemia), INJECTION SITE PAIN (injection site pain), UNEVALUABLE EVENT (good and bad days), HEADACHE (mild headache) and PAIN IN EXTREMITY (Pain in arm) in an 82-year-old male patient who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.     The patient's past medical history included Skin cancer (history of squamous loss/bit of cancer on arm/skin cancer/cancer was taken off) and Skin cancer excision. Previously administered products included for an unreported indication: INFLUENZA VACCINE on 01-Nov-2018, INFLUENZA on 28-Oct-2019 and INFLUENZA VACCINE on 10-Oct-2020. Concomitant products included ADALIMUMAB (HUMIRA) for Colitis ulcerative.    On 25-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On an unknown date, the patient experienced IRON DEFICIENCY ANAEMIA (iron deficiency anemia), INJECTION SITE PAIN (injection site pain), UNEVALUABLE EVENT (good and bad days), HEADACHE (mild headache) and PAIN IN EXTREMITY (Pain in arm). At the time of the report, IRON DEFICIENCY ANAEMIA (iron deficiency anemia), INJECTION SITE PAIN (injection site pain), UNEVALUABLE EVENT (good and bad days), HEADACHE (mild headache) and PAIN IN EXTREMITY (Pain in arm) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 03-Mar-2021, Blood folate (<3.9-Unknown): 16.2 Folate: 16.2 (normal less than 3.9). On 03-Mar-2021, Blood iron (80-160): 109 mcg/dl Iron: 109 MCG/DL (normal 80 to 160). On 03-Mar-2021, Haematocrit (41-51 percent): 38.0% percent hematocrit: 38.0% (normal 41.0 to 51.0). On 03-Mar-2021, Haemoglobin: 12.2 gm/dl Hemoglobin 12.2 GM/DL. On 03-Mar-2021, Iron binding capacity total (254-457): 403 mcg/dl Iron Binding: 403 MCG/DL (normal 254 to 457). On 03-Mar-2021, Mean cell haemoglobin: 31.3 pg/cell MCH: 31.3 PG/CELL. On 03-Mar-2021, Mean cell haemoglobin concentration (32.0-36.0): 32.1 g/dl MCHC: 32.1 G/DL (normal 32.0 to 36.0). On 03-Mar-2021, Mean cell volume (80-99): 97.4 fl MCV: 97.4 FL (normal 80 to 99). On 03-Mar-2021, Red blood cell count (4.4-6.0): 3.90 10**12/l RBC: 3.90 10**12/L (normal 4.4 to 6.0). On 03-Mar-2021, Red cell distribution width (<15.0-Unknown): 13.2% RDW: 13.2% (normal less than 15.0). On 03-Mar-2021, Reticulocyte count (2.3-15.9 percent): 11.4% percent Immature Reticulocyte Fraction; 11.4% (normal 2.3 to 15.9). On 03-Mar-2021, Reticulocyte haemoglobin equivalent: 34.5 pg/cell Reticulocytes Hemoglobin: 34.5 PG/CELL. In the absence of hemoglobinopathy, a less than normal hemoglobin content in the reticulocytes is an indication of inadequate iron supply relative to demand.. On 03-Mar-2021, Reticulocyte percentage (0.5-1.5): 1.9% Reticulocyte percent: 1.9% (normal 0.5 to 1.5). On 03-Mar-2021, Serum ferritin (30-400): 13 ng/ml ferritin 13 NG/ML (normal 30 to 400). On 03-Mar-2021, Transferrin saturation (20-55 percent): 27% percent Percent iron saturation: 27% (normal 20 to 55). On 03-Mar-2021, Vitamin B12 (211-946): 774 pg/ml Vitamin B12: 774 PG/ML (normal 211 to 946).     The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.   For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter considered HEADACHE (mild headache) and PAIN IN EXTREMITY (Pain in arm) to be possibly related. No further causality assessments were provided for IRON DEFICIENCY ANAEMIA (iron deficiency anemia), INJECTION SITE PAIN (injection site pain) and UNEVALUABLE EVENT (good and bad days).    Additional lab information: On an unknown date, a blood test showed Anemia. On an unknown date, a CBC with differential showed Anemia. On an unknown date, Iron/Total Iron Binding Capacity was unknown.  It was reported onset date for Iron Deficiency Anemia and Mild Headache was in 2021.  No treatment information was provided.