Not all out-of-range results are equally urgent. Labs use two flags to distinguish degrees of concern, and understanding the difference helps you know what to do when you see them.
Abnormal results (H/L flags)
A result flagged H (high) or L (low) is outside the reference range but not necessarily dangerous. Many abnormal results are mildly or borderline out of range and require monitoring or lifestyle adjustment rather than immediate action. Your GP will consider the result in the context of your symptoms, your trend and your overall clinical picture before deciding whether to act.
Critical results
Critical values are results so far outside the normal range that immediate clinical action is required — they carry a risk of harm or death if not addressed quickly. Labs are required to contact the ordering clinician immediately when a critical result is generated. Examples include sodium below 120 or above 160 mmol/L, potassium below 2.5 or above 6.5 mmol/L, glucose below 2.5 mmol/L, and platelet count below 20 × 10⁹/L.
If you receive a notification of a critical result in Looms, contact your GP or the ordering centre immediately, or go to A&E if you have symptoms. Do not wait for a scheduled appointment.
What Looms does with flagged results
Looms displays H/L flags alongside each result value and generates a dedicated notification for any result flagged as abnormal or critical by the issuing lab. Critical results generate a high-priority alert that bypasses quiet hours settings.