Understanding Lab Tests for Infection
Written by Private MD Labs Medical Writing Team • Last Updated: September 8, 2025
An infection occurs when harmful microorganisms such as bacteria, viruses, fungi, or parasites invade the body and multiply. While specific infections are typically diagnosed through targeted tests that identify the particular pathogen, blood tests play a fundamental role in monitoring the body's immune response, assessing inflammation levels, and evaluating overall health status during an infection.
Top Recommended Test
Inflammation test
This test measures how quickly red blood cells settle in a tube over one hour, which indicates inflammation levels in the body. During infections, the sedimentation rate typically increases as the body responds to the infectious process, making it a useful marker for monitoring inflammation.
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Why Blood Testing is Important During Infection
When the body fights an infection, it triggers various immune responses that can be measured through blood tests. These tests help healthcare providers monitor inflammation levels, assess immune system function, and track the body's response to treatment. While they don't identify the specific pathogen causing the infection, they provide valuable information about the severity and progression of the body's inflammatory response.
Other Relevant Tests
Complement Component C3c and C4c
These tests measure complement proteins that are essential components of the immune system's response to infection. During active infections, C3c and C4c levels may decrease as the immune system consumes these proteins while fighting off pathogens, providing insight into immune system activation.
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Post COVID-19 Expanded Panel
This comprehensive panel includes white blood cell counts and other markers that can indicate immune system response to infection. Elevated white blood cell counts often suggest an active infection, while abnormal counts may indicate complications or underlying immune system issues.
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Important Considerations
The information here is for educational purposes only and is not a substitute for professional medical advice. Always consult with a healthcare provider for diagnosis and treatment. Specific pathogen identification may require additional specialized testing beyond these general inflammatory and immune response markers.
