Understanding Lab Tests for Bacterial Infection
Written by Private MD Labs Medical Writing Team • Last Updated: September 8, 2025
Bacterial infections occur when harmful bacteria invade the body and multiply, causing illness. While the specific bacteria may vary, blood tests can effectively detect the body's immune response to these infections, providing valuable diagnostic information to guide treatment decisions.
Top Recommended Test
Complete Blood Count / CBC (includes Differential and Platelets)
This comprehensive test provides detailed information about different types of white blood cells, including neutrophils. High neutrophil levels are particularly indicative of bacterial infections, as these cells are the body's primary defense against bacteria.
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How Blood Tests Detect Bacterial Infections
When bacteria invade the body, the immune system responds by producing more white blood cells, particularly neutrophils, to fight the infection. Blood tests can measure these changes in white blood cell counts and patterns, helping healthcare providers distinguish bacterial infections from viral infections or other conditions.
Other Relevant Tests
White Blood Cell Count (WBC)
This test measures the total number of white blood cells in your blood. An elevated WBC count is a key indicator of bacterial infection, as your immune system produces more white blood cells to combat the invading bacteria.
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Post COVID-19 Expanded Panel
This panel includes neutrophil count analysis, which can help identify bacterial infections. Elevated neutrophils may indicate bacterial infection, especially in patients recovering from COVID-19 who may be at increased risk for secondary bacterial infections.
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Understanding Your Results
Elevated white blood cell counts, particularly neutrophils, strongly suggest a bacterial infection and help differentiate it from viral infections, which typically show different patterns in blood work. Your healthcare provider will interpret these results alongside your symptoms to determine the most appropriate antibiotic treatment.
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.
