Planning a long trip usually means a checklist: passport, insurance, vaccines. For some travellers it also raises health questions. Is a twelve-hour flight a concern given my history? Do I still have protection from the rabies vaccine I had years ago? And what if I come home with a fever?
This article looks at the blood tests before travel that are in the BPR catalogue, plus one test that belongs to the return journey. It explains what each measures and when it tends to be considered. It does not replace a travel health consultation.
Start with a travel health professional
Travel vaccines protect against illnesses usually found in other countries, and the ones you need depend on where you are going and where in that country you will be (NHS, Travel vaccinations). Some are free on the NHS, such as hepatitis A and typhoid, while others, including rabies and yellow fever, have to be paid for (NHS, Travel vaccinations). A travel health professional looks at your specific itinerary and decides what makes sense.
The NHS recommends getting advice from a travel health professional at least 4 to 6 weeks before you travel, because some vaccines need a course of doses and others take time to build protection (NHS, Travel vaccinations). Blood tests, when needed, fit into that plan rather than replacing it.
Long flights and blood clots: the Pre-Travel Screen (DVT)
DVT (deep vein thrombosis) is a blood clot in a deep vein, usually in the leg. The NHS lists a long journey of more than 4 hours by plane, car or train among the times when the chance of DVT is higher, alongside other factors such as recent surgery, pregnancy, a previous DVT or thrombophilia (NHS, DVT).
A 2025 review on travel-associated thrombosis explains that prolonged immobility, dehydration and cabin conditions all play a part. The absolute risk is relatively low in the general population, but it rises in higher-risk groups, including people with a past clot, thrombophilia, pregnancy or recent surgery (Papadakis et al., 2025).
The Pre-Travel Screen (DVT) in the LML catalogue is described by LML as a test of DVT risk before travelling. It reports three markers:
- Anticardiolipin Antibodies (IgG)
- Anticardiolipin Antibodies (IgM)
- Factor II (Prothrombin) Assay
LML asks for clinical history to be provided with this test, and results are usually available five days after the sample reaches the laboratory. Because the risk depends so much on personal history, this test is best discussed with a doctor, who can also advise on practical measures. The NHS suggests loose clothing, plenty of water, avoiding alcohol and walking around when possible on journeys of 4 hours or more (NHS, DVT).
If you develop pain and swelling in one leg, or chest pain or breathlessness, during or after a trip, seek urgent medical help. The NHS advises calling 999 when leg symptoms come with chest pain or shortness of breath (NHS, DVT).
Yellow fever antibodies
Some countries require a yellow fever certificate. The NHS explains that the vaccine is recommended if you are travelling to an area where yellow fever is found or need a certificate, and that it is only available from registered yellow fever centres (NHS, Yellow fever).
The Yellow Fever Antibodies test measures antibodies specific to the yellow fever virus. LML describes yellow fever as a mosquito-borne illness and notes that the test can help investigate an acute or recent infection. LML asks for clinical and travel history with the sample, and results take about 2 weeks. This test is not a substitute for the vaccination certificate, which is what border authorities ask to see.
Rabies antibody
Rabies vaccination before travel is one of the travel vaccines that is not routinely available on the NHS and has to be paid for (NHS, Travel vaccinations). Some travellers had a course years ago and are unsure where they stand.
The Rabies Antibody test measures antibodies against the rabies virus. LML explains that it is used to see whether someone has developed immunity, either through vaccination or previous exposure. People who work with animals or who had their vaccine course some time ago sometimes ask about it. Results take about 2 weeks.
A blood test is not the way to deal with an animal bite or scratch abroad. In that situation, speak to a medical professional promptly rather than waiting for a test.
