A common cold is a viral infection that affects the upper respiratory tract, including the nose, throat, sinuses, and windpipe. It is typically caused by various viruses, most frequently rhinoviruses. Blood tests serve as important tools in healthcare, offering insights into overall physiological states, helping to detect various conditions, and monitoring organ function or the effectiveness of treatments.
The Body’s Response to a Cold
When a cold virus enters the body, the immune system initiates a coordinated defense. The cells lining the nose and throat release chemical messengers called cytokines. These cytokines alert the body to the infection, triggering a localized inflammatory response. This process involves the dilation of blood vessels, allowing more infection-fighting white blood cells to travel to the affected area.
The immune system’s activation is a systemic process, affecting the entire body. As white blood cells mobilize and inflammation occurs, these physiological changes can temporarily alter various markers in the bloodstream. The body’s effort to combat the virus causes certain components measured in blood tests to fluctuate from their normal baseline levels.
Blood Tests Affected by a Cold
A common cold can influence the results of certain blood tests due to the body’s immune response. For instance, a complete blood count (CBC) measures components of your blood, including white blood cells (WBCs). During a cold, your WBC count, particularly neutrophils, might temporarily increase as the body fights the infection, while lymphocytes could decrease.
Inflammatory markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), are also sensitive to the presence of a cold. CRP levels, produced by the liver in response to inflammation, can show a mild to moderate elevation during a viral infection like a common cold. Similarly, ESR, which measures how quickly red blood cells settle, can increase due to the inflammation associated with a cold. However, other common blood tests, such as cholesterol panels or routine thyroid function tests, are generally not significantly impacted by a cold. Glucose levels might temporarily rise due to stress hormones released during illness, especially in individuals with diabetes.
Deciding on Your Blood Test
If you have a cold and a blood test scheduled, it is generally advisable to communicate with your healthcare provider. The temporary changes in blood markers caused by an active infection can lead to skewed results, making it difficult to interpret your true baseline health status. For routine check-ups or tests that are not urgent, rescheduling until you feel better, ideally a few days after symptoms resolve, can ensure more accurate results.
However, if the blood test is for diagnosing an acute illness, monitoring a chronic condition, or addressing urgent symptoms, your doctor might recommend proceeding with the test. In such cases, the medical team will consider your current symptoms and health status when interpreting the results. Discussing the purpose of your blood test and the severity of your cold symptoms with your healthcare provider will help determine the best course of action.