Most of what people are told after a PE is sensible. Some of it has evidence behind it, some of it is habit, and one common instruction is actually wrong. This chapter sorts them.
1. What changes the risk of another one
| Factor | What the evidence says | What to do |
|---|---|---|
| Continuing anticoagulation after an unprovoked clot | The single biggest lever: recurrence falls by around 80–90% while on treatment | The three-month decision, revisited yearly |
| Oestrogen (combined pill, HRT tablets) | Raises clot risk 2–4 fold; a clot on oestrogen is provoked, and restarting it is a recurrence risk | Stop; use a progestogen-only or non-hormonal method. Transdermal HRT carries much less risk than tablets if HRT is needed — a specialist decision |
| Obesity | Roughly doubles the risk of VTE and of recurrence | Weight loss helps; there is no trial showing it prevents recurrence, but the direction is not in doubt |
| Immobility | The strongest transient trigger | Move early after surgery and illness; if a future admission or operation is planned, tell the team about the PE so prophylaxis is given |
| Smoking | A modest risk factor for VTE, a large one for everything else | Stop |
| Cancer | The strongest persistent risk factor | Report new symptoms; keep to screening programmes |
| Sitting still for four hours or more, in any seat | Roughly doubles the risk, for cars, coaches and trains as much as flights (section 4) | Move hourly; stockings and, for the highest risk, an injection for long journeys; never aspirin for this |
| Dehydration | Widely believed, weakly evidenced | Drink normally; it is not a treatment |
| Compression stockings | Do not prevent recurrence or post-thrombotic syndrome after a DVT (NICE 1.7.5) | Not for prevention. Fine for leg symptoms if they help |
2. Exercise after a PE
Bed rest is not a treatment for a PE and has not been for twenty years. Once anticoagulation is established, walking is encouraged from the first day. Breathlessness on exertion in the first weeks is expected: the clot is still there, the lung is inflamed, and fitness has been lost. The evidence for structured rehabilitation is small but consistent: supervised exercise programmes after PE improve walking distance and quality of life, and the fear of "dislodging" a clot by exercising is not supported once treatment has started. Build back gradually over four to twelve weeks, and let symptoms set the pace. Contact sports and anything with a real risk of head injury are a separate question while anticoagulated, discussed below.
The exception is persisting or worsening breathlessness at three months, which needs the echocardiogram described in the after-hospital chapter before pushing harder.
3. Living on an anticoagulant
- Bleeding. Nosebleeds and gum bleeding that stop within ten minutes are common and usually fine. Black stools, red or dark urine, coughing or vomiting blood, a head injury of any kind, or a bleed that will not stop are same-day medical problems.
- Other medicines. Anti-inflammatory painkillers (ibuprofen, naproxen, aspirin) add bleeding risk and are generally avoided; paracetamol is the usual choice. Some antibiotics, antifungals and anti-epileptics change DOAC levels. Tell every prescriber and the pharmacist, and check supplements: St John's wort lowers DOAC levels, and several "natural blood thinners" are unquantified.
- Alcohol. Moderate amounts do not interact with DOACs. Heavy drinking raises bleeding risk, mostly through falls and the stomach lining.
- Dentists and operations. Routine dental work is usually done without stopping the drug. Anything larger needs a plan for a short interruption; it is the prescriber's job to make it, not the dentist's.
- The alert card. Carry it. In an accident, the first thing an emergency team needs to know is what you are taking.
- Sport. Running, cycling, swimming and gym work are all fine. Rugby, boxing, martial arts, downhill mountain biking and similar carry a bleeding risk, principally to the head, that is real while on treatment; it is a personal decision with the numbers in front of you.
4. Sitting still: flights, cars, coaches, trains and desks
The risk is sitting still, not flying. The World Health Organization's WRIGHT project and the Dutch MEGA study both found that any journey of four hours or more in which you stay seated and immobile roughly doubles the risk of a clot, and that the risk is the same whether the seat is on a plane, in a car, on a coach or on a train. It rises with the length of the journey and with several journeys close together. The absolute risk for an average traveller is low, around one clot per 4,000–6,000 long journeys; it is highest in the first week afterwards and stays raised for about four to eight weeks, which is why a leg or chest symptom in the month after a long trip should be mentioned. The same mechanism applies to a day spent motionless at a desk or a games console: case series exist, the evidence is thinner, and the remedy is the same.
Who is at real risk. The doubling multiplies whatever your baseline is. In the MEGA study the risk of a clot after overland travel was about eight times higher in carriers of factor V Leiden, ten times higher with a body mass index over 30, five times higher in people over 1.90 m, and more than twenty times higher in women on the combined pill; on flights, very short people were at extra risk too. Add a previous clot, recent surgery, cancer, pregnancy or the weeks after birth, and the calculation changes from "nothing needed" to "do something". The British Society for Haematology and the NHS travel health service both grade the advice by that risk.
| When | Everyone | Higher risk (a previous clot, recent surgery, cancer, pregnancy, oestrogen, obesity, a known thrombophilia) |
|---|---|---|
| Before | Book an aisle seat; wear loose clothing; on a drive, plan a stop every one to two hours | Below-knee graduated compression stockings, properly fitted, 15–30 mmHg at the ankle: the one setting where stockings have trial evidence, reducing symptomless DVT on flights. For the highest risk and off anticoagulation, ask about a single injection of low-molecular-weight heparin one to two hours before departure. If you are on an anticoagulant, you are protected and need nothing extra |
| During | Walk for a few minutes every hour; calf exercises in the seat (ankle circles, heel-toe raises) every half hour; do not cross your legs or sleep curled up; drink water; keep alcohol modest — it dehydrates and, more to the point, sedates, so you move less; no sleeping tablets. In a car, the driver stops and walks every one to two hours and the passengers do the same | All of that, plus the stockings for the whole journey, and not sleeping through a long-haul flight without moving |
| After | Move as soon as you can; know the symptoms for the following month | The same; a leg or chest symptom in the weeks after travel is a same-day assessment, and say you have travelled |
Aspirin: not before, not during, not after. Aspirin is good at preventing clots in arteries and poor at preventing them in veins. The American College of Chest Physicians guideline suggests against aspirin or any anticoagulant for ordinary long-distance travellers, the NHS travel health service says aspirin is not recommended for travel-related venous thrombosis, and the one small trial that tested it found no convincing benefit and more stomach bleeding. Where prevention is needed, it is stockings and, for the highest risk, a single injection — not a tablet bought at the airport.
Most airlines and the Civil Aviation Authority advise not flying for at least a fortnight after a PE, and until symptoms have settled and treatment is established; check with the airline's medical service for anything sooner. The same fortnight is sensible after a DVT before a long car or coach journey, for the same reason: the clot is at its most unstable in the first two weeks.
5. Future surgery and hospital admissions
A previous VTE is one of the highest-weighted items on the NHS admission risk assessment. Tell every admitting team, and expect prophylactic heparin injections and mechanical compression for any operation or medical admission. If you are still on an anticoagulant, the surgical team needs to plan when to stop it and when to restart, and for very high-risk cases whether to bridge with heparin. If you have stopped, ask whether a short course of prophylaxis after the operation is planned; for hip and knee replacement it always should be.
6. Contraception, HRT and pregnancy
Contraception. The combined pill, patch and ring are contraindicated after a VTE. The progestogen-only pill, the implant, the hormonal coil and the copper coil are all acceptable; the injectable (medroxyprogesterone) is generally avoided. This is a decision for the first review, not a later one, because a pregnancy on a DOAC is a problem.
HRT. Oral HRT raises VTE risk; transdermal oestrogen in standard doses does not appear to, on the observational evidence. After a VTE, HRT is a specialist decision, and if it is given it is transdermal, usually with anticoagulation continuing.
Pregnancy. DOACs cross the placenta and are stopped before conception or as soon as pregnancy is confirmed. A previous VTE means prophylactic low-molecular-weight heparin throughout pregnancy and for six weeks after birth, arranged through an obstetric haematology clinic. Plan the pregnancy with them rather than announcing it. Breastfeeding on warfarin or heparin is safe; DOACs are not recommended.
7. If you have finished anticoagulation: the plan to avoid a repeat
Most people whose clot was provoked stop treatment at three months, and some people with an unprovoked clot choose to stop after the review. Off treatment, the protection is no longer in a tablet; it is in knowing which situations raise the risk and having a plan for each. The recurrence risk after a provoked clot with the trigger gone is low, around 1–3% a year; after an unprovoked clot it is roughly 10% in the first year off treatment, which is why that decision is a shared one. Either way, the plan is the same.
| Situation | What to do |
|---|---|
| Any hospital admission or operation | Say "I have had a DVT / PE" at the first contact. Expect heparin injections and leg sleeves; after major surgery, expect to go home with injections for two to five weeks (the prevention chapter has the durations). If nobody mentions it, ask |
| A leg in a cast, a bad injury, or a spell in bed | Ask the GP or fracture clinic about a short course of injections for the duration; keep the other leg and the rest of you moving |
| Long journeys over four hours, by any means | Aisle seat or planned stops, walk hourly, calf exercises, water, alcohol modest, no sedatives; below-knee stockings for the journey; and for an unprovoked history, ask about a single injection before travel. Not aspirin (section 4) |
| Pregnancy | Plan it with an obstetric haematology clinic before conception; expect injections throughout and for six weeks after birth |
| Hormones | Never the combined pill, patch or ring again; progestogen-only or non-hormonal contraception; HRT only transdermal and only with specialist advice |
| A new cancer diagnosis | Tell the oncology team about the clot history; many cancer treatments carry clot risk and prophylaxis may be advised |
| A second clot | A second unprovoked clot usually means lifelong anticoagulation. Vigilance is the point: a clot caught early is a tablet; a clot caught late is a pulmonary embolism |
Every day: keep moving (150 minutes a week of moderate activity, and never a whole day in a chair); keep weight down; stop smoking; drink alcohol within 14 units; drink normally and ignore hydration myths. Know the symptoms — one-sided leg swelling or pain, sudden breathlessness, pleuritic chest pain, coughing blood, collapse — and where to go the same day; the local DVT service or A&E, not a routine appointment. Make sure the clot is on your GP record and on any hospital "alert" system, and mention it on any medical form. A yearly GP review is not required once you are off treatment, but it is sensible: weight and blood pressure, a check that your screening is up to date, and the question of whether anything has changed the case for anticoagulation.
What does not help: daily aspirin, unless you chose it at the review as a substitute for anticoagulation (it roughly halves recurrence for a while, well short of an anticoagulant, and it bleeds); compression stockings to prevent recurrence; "natural blood thinners", fish oil, garlic, turmeric, nattokinase or vitamin E for this purpose; detoxes; and private "thrombophilia screens" or MTHFR tests (the every-test chapter says why).
8. Where UK and US guidance differ
The US guidance says less about lifestyle than NICE does and does not address stockings or travel. Where the American Society of Hematology and the British Society for Haematology have both written on travel and hormones, they agree. The one difference of emphasis is that US practice more often continues oral HRT with anticoagulation in women who want it; UK practice prefers transdermal. Neither has trial evidence.