Small amount of blood clots; Potassium levels dropped; Increased hypertension; dizziness; Arm pain from her elbow to shoulder; Shortness of breath; Blood pressure increased; fatigue; chills; Hear arm was hot  to touch; Itchiness; Red circle near injection site the size of a quarter; not to take the second dose; This spontaneous case was reported by a consumer and describes the occurrence of THROMBOSIS (Small amount of blood clots) and HYPOKALAEMIA (Potassium levels dropped) in a 44-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 026A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included No adverse reaction.    On 15-Mar-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 23-Mar-2021, the patient experienced VACCINATION SITE ERYTHEMA (Red circle near injection site the size of a quarter). On 24-Mar-2021, the patient experienced VACCINATION SITE WARMTH (Hear arm was hot  to touch) and VACCINATION SITE PRURITUS (Itchiness). On 25-Mar-2021, the patient experienced PAIN IN EXTREMITY (Arm pain from her elbow to shoulder), DYSPNOEA (Shortness of breath), BLOOD PRESSURE INCREASED (Blood pressure increased), DIZZINESS (dizziness), FATIGUE (fatigue) and CHILLS (chills). On 01-Apr-2021, the patient experienced THROMBOSIS (Small amount of blood clots) (seriousness criterion medically significant), HYPOKALAEMIA (Potassium levels dropped) (seriousness criterion medically significant) and HYPERTENSION (Increased hypertension). On an unknown date, the patient experienced PRODUCT DOSE OMISSION ISSUE (not to take the second dose). At the time of the report, THROMBOSIS (Small amount of blood clots), HYPOKALAEMIA (Potassium levels dropped), PAIN IN EXTREMITY (Arm pain from her elbow to shoulder), DYSPNOEA (Shortness of breath), BLOOD PRESSURE INCREASED (Blood pressure increased), HYPERTENSION (Increased hypertension), VACCINATION SITE WARMTH (Hear arm was hot  to touch), DIZZINESS (dizziness), VACCINATION SITE PRURITUS (Itchiness), FATIGUE (fatigue), VACCINATION SITE ERYTHEMA (Red circle near injection site the size of a quarter) and CHILLS (chills) outcome was unknown and PRODUCT DOSE OMISSION ISSUE (not to take the second dose) had resolved.        The action taken with mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) was unknown.       On 01-Apr-2021 patient went to the ER for 2 hours. The HCP at the ER stated she had increased hypertension, potassium levels dropped and there was a small amount of blood clots. Her primary care physician said not to take the second dose. Patient inquired about what she can do to manage her symptoms. Concomitant drugs were not reported. Treatment information was not provided.  Based on the current available information and temporal association between the use of the product and the start date of the event, a causal relationship cannot be excluded. However, Further information is requested.; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the event, a causal relationship cannot be excluded. However, Further information is requested.