Category A vs Category B
Biological Substances
The difference between Category A and Category B biological substances determines how a specimen must be packaged, marked, and shipped — and getting it wrong is a serious compliance failure.
Before a single specimen ships, it has to be classified. The line between Category A and Category B biological substances decides everything that follows: packaging, marking, paperwork, and which carriers will even accept the package. This guide explains the difference in plain terms.
The core distinction: Category A substances can cause permanent disability or life-threatening disease in otherwise healthy people. Category B cannot. That single difference drives two very different sets of rules.
Category A: The Strict Tier
Category A covers infectious substances capable of causing permanent disability, life-threatening, or fatal disease in humans or animals. They ship under UN2814 (affects humans) or UN2900 (affects animals only). Requirements are stringent: certified packaging tested to rigorous standards, a formal dangerous-goods declaration, trained shippers, and specific carrier programs. Most routine labs never handle Category A — and a compliance-first courier may decline it entirely rather than risk mishandling.
Category B: The Routine Tier
Category B — UN3373, "Biological Substance, Category B" — covers biological material being shipped for diagnostic or investigational purposes that does not meet the Category A threshold. This is the overwhelming majority of patient specimens: routine blood, urine, stool, and swab samples. The rules are real but far simpler: triple packaging, a UN3373 mark, and the proper shipping name — no formal hazmat declaration required.
How to Classify a Specimen
- Start with the diagnosis or suspicion. What pathogen might be present, and what disease could it cause in a healthy person?
- Check the indicative list. Regulations include a list of substances presumed Category A (certain cultures and high-risk pathogens).
- Consider the form. A patient specimen taken for routine testing is usually Category B; a concentrated culture of a dangerous pathogen is likely Category A.
- When in doubt, escalate. Misclassifying Category A as Category B is a serious violation. If uncertain, treat it as the higher category or consult a hazmat specialist.
Exempt Human Specimens
There's a third bucket: specimens with minimal likelihood of containing pathogens can ship as "Exempt Human Specimen" with lighter requirements — though they still need basic leak-proof packaging. Correct classification here avoids both over-packaging and under-packaging.
Bottom line: Classification is the first and most important compliance decision. Most diagnostic work is Category B (UN3373). Anything that could be Category A demands specialist handling — never guess.
Frequently Asked Questions
Is a routine blood sample Category A or B?
A routine patient blood sample drawn for diagnostic testing is almost always Category B (UN3373), unless it is known or suspected to contain a Category A pathogen capable of causing life-threatening disease.
What UN numbers apply to each category?
Category A uses UN2814 (infectious to humans) or UN2900 (infectious to animals only). Category B uses UN3373.
Do you handle Category A shipments?
No. We focus on UN3373 Category B and exempt human specimens. Category A requires specialized certified packaging and handling outside our circle of competence, and we won't compromise on that.
Related Services
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