How to Send a Blood Sample for a DNA Test in England

Home DNA tests usually involve sending samples back to the laboratory. When the sample is a dry cheek swab, the return process is generally simple. A liquid blood sample is different. In England, the correct return method depends on how the specimen is classified for transport and on the carrier’s own rules.

Saliva samples and blood samples do not follow the same return logic

For most at-home DNA tests, saliva or buccal swabs are the easiest option because they are dry, lightweight and simpler to package. Liquid blood samples require more care because transport law distinguishes between specimens that are considered exempt and those that must be shipped as UN 3373 Biological Substance, Category B.

If you want to understand the broader collection rules before arranging shipment, see our guide to DNA samples and collection methods.

How blood samples are classified for transport

A blood sample is not automatically a dangerous good. Under current transport rules, patient specimens with a minimal likelihood that pathogens are present may travel as an Exempt human specimen, provided they are packed correctly and marked accordingly. If the sample does not qualify for that exemption, or if infection risk cannot be ruled out, it may need to be shipped as UN 3373 Biological Substance, Category B instead.

This distinction matters because the label, packaging standard and carrier options are not the same. For an official UK reference, consult the UK guidance on packaging and transport of patient samples.

When the sample is an exempt human specimen

If the specimen qualifies for the exemption, the package must still prevent leakage. IATA states that the packaging must include three components:

• a leak-proof primary receptacle

• a leak-proof secondary packaging

• a strong outer packaging

For liquid samples, sufficient absorbent material must be placed between the primary receptacle and the secondary packaging, and the outside must be marked “Exempt human specimen”.

When the sample is UN 3373 Category B

If the blood sample must travel as UN 3373, the return shipment has to comply with Packing Instruction 650. In the UK, Post Office guidance states that Biological Substances Category B are allowed only for UK domestic mail, not for international mail, and only when sent by or at the request of a qualified healthcare professional or recognised laboratory. The same guidance also imposes a 50 ml / 50 g limit per parcel and requires PI650-compliant packaging.

In practical terms, that means you should never assume that an overseas blood return can be dropped into standard mail. If your laboratory is outside the UK, the safest approach is to follow the exact return process provided by the lab and use the courier route it approves. That conclusion follows directly from the UK mailing restrictions above.

Packaging requirements for a liquid clinical specimen

Whether the sample is shipped as an exempt specimen or as UN 3373, the packaging must be robust enough to protect the contents during normal transport. For liquid specimens, the core requirements are consistent:

• a tightly closed primary tube

• a leak-proof secondary layer

• enough absorbent material to soak up the full contents if the tube leaks

• a rigid or otherwise adequate outer package

• separation or individual wrapping if several fragile tubes are packed together

That is why a properly organised DNA test involving blood should never rely on improvised household packaging. A serious laboratory either supplies the correct materials or gives precise instructions on the approved return format. If you are dealing with a prenatal case, our article on how to take a blood sample for a prenatal DNA test explains the collection side of the process in more detail.

DNA samples are not automatically hazardous materials

This is one of the most important corrections to make to the original text. A DNA sample is not automatically treated as hazardous cargo. In transport law, infectious substances are regulated within Division/Class 6.2, but the rules depend on classification. Some patient specimens can be exempt; others must travel as UN 3373; clinical waste is treated differently again.

So the right question is not, “Is blood always dangerous goods?” The right question is, “How has this sample been classified for transport?” That is what determines the label, the packaging standard and the carrier you may use.

Do not confuse a test sample with medical waste

A blood tube sent for laboratory analysis is not the same thing as clinical waste. UK postal guidance treats Biological Substances Category B and clinical and medical waste as separate categories, with different rules. That distinction is important because people often assume that any blood-containing package is automatically prohibited, which is not accurate.

Sending a sample abroad: customs and courier paperwork

If the return shipment is going to another country, customs formalities may apply in addition to transport rules. In practice, the laboratory or courier may ask for a commercial invoice or related customs documents, even when the sample has little or no commercial value. That is another reason why international returns should be handled exactly as instructed by the laboratory or courier service.

Before shipping internationally, verify four points:

• the exact classification of the sample

• the carrier authorized for that route

• the packaging format required by the laboratory

• the customs paperwork expected by the courier

Choose a reliable laboratory before sending any blood sample

Shipping rules are only one part of the process. The reliability of the result also depends on the laboratory’s procedures, accreditation and sample handling standards. Before paying for any blood-based DNA test, it is worth reviewing our guide to accreditation and reliability of DNA tests.

Conclusion

Sending a blood sample for a DNA test in England is perfectly possible, but it is not handled in the same way as mailing a saliva swab. The key issue is classification: some samples may travel as Exempt human specimen, while others must go as UN 3373 Category B under stricter rules. Packaging, labelling, carrier choice and international paperwork all depend on that first step.

Before sending anything, do not improvise. Check the laboratory’s instructions, use the packaging it recommends, and confirm whether the return can go by post or must go by courier. That simple check can prevent rejected samples, delays and regulatory mistakes.