Blood clots (thrombosis) and Covid-19

The coronavirus outbreak is changing the way we all live our lives, often this means thinking how to adapt and learning to live with uncertainty.

Despite the impact of the virus, the Thrombosis UK team are striving to provide continued support and information to all those affected by thrombosis and anyone who may be at risk, want to learn more or who is involved in blood clots -venous thromboembolism (VTE) prevention and care.

Working with our medical leads and following published advice from Public Health and NHS England, Thrombosis UK is committed to providing information on reducing VTE risks, supporting well-being and any known information on thrombosis and COVID-19.



What we understand about COVID-19 vaccines

Listen to Prof Beverley Hunt OBE on Inside Science discuss many questions and considerations as more is learned about the rare thrombosis and thrombocytopenia syndrome.

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AstraZeneca COVID-19 vaccine and under 30 year olds.

Prof Beverley Hunt OBE is interviewed on BBC Newsbeat

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13 April 2021 - Updated information sheet on COVID-19 vaccination from PH England

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After your COVID-19 Vaccination

By getting the COVID-19 vaccination you are helping to protect yourself and others.

We have prepared this document to help inform you about how you might feel once you have had the vaccination and how you can expect to feel in the next few days, as well as where to get more information.

Download the Leaflet

Letter from the Expert Haematology Panel and endorsed by Thrombosis UK, to the Medicines and Healthcare products Regulatory Agency (MHRA)

We wish to raise our concern with the MHRA regarding wording included in recent changes in MHRA guidance on the use of the AstraZeneca COVID-19 vaccine.

Read the Article



7th April 2021 the Medicines and Healthcare products Regulatory Agency (MHRA) issued new advice concluding there is a possible link between AstraZeneca COVID-19 Vaccine and extremely rare and unlikely to occur blood clots.

The benefits of vaccination continue to outweigh any risks but we are advising that careful consideration be given to people who are at higher risk of specific types of blood clots because of their medical condition.

The scientific review of UK reports of extremely rare and unlikely to occur specific blood clots with lowered platelets has concluded that the evidence of a link with COVID-19 Vaccine AstraZeneca is stronger but more work is still needed.

By 31 March, 20.2 million doses of the COVID-19 Vaccine AstraZeneca had been given in the UK meaning the overall risk of these blood clots is approximately 4 people in a million who receive the vaccine. We would advise that anyone who did not have these side effects should come forward for their second dose when invited.

The data suggest there is a slightly higher incidence reported in the younger adult age groups and we are advising that this evolving evidence should be taken into account when considering the use of the vaccine.

MHRA has issued updated guidance for healthcare professionals on how to minimise risks, as well as further advice on symptoms for vaccine recipients to look out for 4 or more days after vaccination.

See MHRA website for more information



JCVI statement on use of the AstraZeneca COVID-19 vaccine
April 07th 2021

Since the start of the pandemic over 4 million COVID-19 infections have been confirmed in the UK causing more than 120,000 deaths. Over 30 million people have received their first dose of COVID-19 vaccine since the start of the programme, which Public Health England (PHE) estimate has prevented at least 6,000 deaths in the first 3 months of 2021. Analysis of infection data since the introduction of the COVID-19 vaccines in the UK demonstrates that vaccination is highly effective and substantially reduces the risk of infection and severe COVID-19 disease.

There have been reports of an extremely rare adverse event of concurrent thrombosis (blood clots) and thrombocytopenia (low platelet count) following vaccination with the first dose of AstraZeneca ChAdOx1 nCoV-19 vaccine (AZD1222). There has been no signal for thrombosis/thrombocytopenia following receipt of other COVID-19 vaccines approved for use in the UK (Pfizer-BioNTech and Moderna). Given the very low numbers of events reported overall, there is currently a high level of uncertainty in estimates of the incidence of this extremely rare adverse event by age group. However, the available data do suggest there may be a trend for increasing incidence of this adverse event with decreasing age, with a slightly higher incidence reported in the younger adult age groups. In contrast, the risks of severe disease associated with COVID-19 increases steeply with age, with the youngest adults at lowest risk. There are currently no known risk factors for this extremely rare condition, which appears to be an idiosyncratic reaction on first exposure to the AstraZeneca COVID-19 vaccine.

Read the full statement at: https://www.gov.uk/



COVID-19 vaccination programme in the UK
March 16th 2021

COVID vaccination and blood clots:

Recent news has highlighted pausing of the Astra Zeneca COVID vaccination in some countries due to concern about reported blood clots in a small number of people shortly after receiving the vaccination. It is important that all adverse events are reported and investigated.

The risk of a deep vein thrombosis (DVT) or pulmonary embolism (PE) in a healthy person is less than 1/1000 per year. We need to remember the risk of DVT/PE increases with age and that we are currently vaccinating the very oldest in our population.

Based on current evidence which has been reported as 37 per 17 million (who will be mainly over 60s) this is very low and less than the background risk associated in the general population. Thrombosis UK agree with statements from UK Medicines Healthcare products Regulatory Agency (MHRA), the World Health Organisation (WHO) and the European Regulatory Agency (ERA) that there appears to be no association or link between receiving this vaccination and the development of blood clots.

Read full UK Medicines and Healthcare products Regulatory Agency (MHRA) response



Group 6 COVID-19 vaccination programme in the UK
February 24th 2021

We delighted to hear that a few of our followers in the UK have already been called for their COVID 19 vaccination within the Risk Group 6 Cohort.

We are pleased to confirm that in the UK, if you have a 'History of Venous Thromboembolism' and are over the age of 16 you qualify to receive the COVID-19 vaccination within the Group 6 roll out.

This is regardless of:

  • When you last had a VTE (DVT/PE)
  • Whether you are still on anticoagulation or not
  • Whether you are still on anticoagulation or not
  • Whether your DVT/PE was provoked or unprovoked

For more information on the UK COVD-19 vaccination programme and the 'Risk Group' categories please see the Green Book Chapter 14a

If you have not yet been called please do not worry the roll out is at different stages across the UK and there are huge numbers of patients to be invited. If however you do have any concerns please contact Thrombosis UK for general guidance via email to: clare@thrombosisuk.org



COVID-19 vaccine and anticoagulation
December 9th 2020

The COVID-19 vaccine is given as an injection into your upper arm (intramuscular). Individuals receiving direct oral anticoagulant (apixaban, dabigatran, edoxaban & rivaroxaban) or warfarin in therapeutic INR range or on full dose heparin or fondaparinux injections can all receive the COVID-19 vaccination.

  • There is a risk of bruising at the injection site, but we do not anticipate any serious effects related to anticoagulation
  • We suggest that after the injection prolonged pressure (at least 5 minutes) should be applied to the injection site to reduce bruising
  • Patients on warfarin with supra-therapeutic INR should wait until their INR is <4.0
  • We encourage patients to have vaccinations and should not be avoided on the basis of being on anticoagulation


Please note, if you have any specific concerns or questions about your own health, please speak directly with your healthcare provider. Thrombosis UK is unable to offer individual medical advice and it would be unethical for us to provide you with that level of advice.

Thrombosis and COVID-19, current information:

  1. Having blood clots, such as deep vein thrombosis (DVT) or pulmonary embolism (PE), is not associated with an increased risk of acquiring COVID-19.
  2. Anticoagulants themselves don't place patients at risk for COVID-19. What can be important are underlying disorders. For example, if anticoagulants are given to someone with a blood clot associated with active cancer; then the cancer and its treatment may result in immunosuppression, which places patients at risk. It's important to talk to your doctor about your individual situation if you are concerned.
  3. D-dimer is a non-specific marker of inflammation or infection so it is not surprising that the levels will be high in those with the most severe Covid-19 infection. In some of the articles in the lay press, elevated D-dimer levels have been interpreted as indicating blood clots. This is an incorrect interpretation. Although D-dimer levels are elevated in most patients with blood clots, D-dimer levels also are elevated in many other disorders including infection. Therefore, an elevated D-dimer level in patients with COVID-19 infection alone is not evidence that they have a clot. For to up to date medical guidance and information for the public, in the UK visit: https://www.nhs.uk/conditions/coronavirus-covid-19/. There is also helpful information on the following sites: the World Health Organization (WHO), https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public which includes information on Myth Busters and basic protective measures.

Reducing your risk of blood clots while working from home or self-isolating

Being aware of risk factors, and especially of your own risk factors is really important in helping you to avoid and protect yourself from thrombosis.

Although some risk factors including hospitalisation and major surgery, carry more risk, if you are at home and less active, this can also be a risk factor for deep vein thrombosis, for instance:

  • Long-term bed rest
  • Long periods of inactivity including sitting for long period of time results in blood moving very slowly through the leg veins
  • Dehydration can also risk a risk factor as it causes blood to thicken

Look out for our interactive live Facebook activities to keep you moving and active despite being in self-isolation!

Further details shortly.

Maintaining your well-being while managing self-isolation

Clinical research has demonstrated that the psychosocial impact of venous thromboembolism (VTE) can belong-lasting and even life-changing. As many people will need to self-isolate or move their work to being home-based, it is very important to also support your psychological well-being as well as physical health

Thrombosis UK has a range of aids to help with managing worrying, sleeplessness and anxiety as a result of thrombosis.

Look out for our interactive sessions on relaxation and mindfulness, full details to follow.

Additionally, www.mind.org.uk has published useful information regarding wellbeing and coronavirus, including for those who are self-isolating.


Blood clots, thrombophilia and COVID-19
Prof Beverley Hunt OBE
November 2020



ISTH - COVID-19 and Thrombosis: ‘Ask The Expert’ with Prof Beverley Hunt OBE


Thrombosis & Covid-19, an update

Professor Beverley Hunt OBE, message from Thrombosis UK


Webinar: Patient Information & Support webinar: Thrombosis Q & As’ with Professor Beverley Hunt OBE


Thrombosis UK is delighted to welcome you to its' very first online dedicated Patient Information and Support meeting.

Led by Prof Beverley Hunt OBE, the meeting will offer opportunity to pre-submit questions, learn more about blood clots and hear updates on the management of blood clots, Covid-19 and insight on restoring health and well being following diagnosis of thrombosis.

Watch Video

Anticoagulation during Covid-19

Download Document

Anticoagulation during Covid-19

Dr Matthew Fay GP with Affinity Care PCN Bradford - Trustee Thrombosis UK and Clinical Advisor to Anticoagulation UK


Blood Clots and Covid-19

Professor Beverley Hunt OBE, Consultant Haematologist, and co-Founder & Medical Lead Thrombosis UK.


World Thrombosis Day: Ask the Expert with Jeffrey Weitz, M.D.: COVID 19 and Thrombosis



Prof Beverley Hunt OBE was interviewed by BBC Radio 4 on the Today Programme to discuss the occurrence of thrombosis in severely ill, hospitalised COVID-19 patients. https://www.bbc.co.uk/sounds/p... (45-49 mins into the programme).

If you have experienced a blood clot as a result of Covid-19 we would welcome hearing from you to help raise greater awareness and understanding on this previously unseen challenge. To contact please email jo@thrombosisuk.orgr

We would also welcome hearing from individuals who have a history of thrombosis and in the recent Covid-19 pandemic, developed Covid-19 and have made a full recovery. If you were willing to share your experience it would be extremely reassuring for others with a medical history of thrombosis. Thank you.


Anne was diagnosed with Antiphospholipid Syndrome (APS) in 2015, has a history of blood clots, and then in March 2020, developed COVID-19

I am a 54-year-old female, working as a nurse in the NHS and diagnosed with Antiphospholipid Syndrome in 2015 following an admission to hospital in May 2014 with unprovoked bilateral pulmonary emboli. This is an account of my experience of COVID-19 in March this year. The first sign I had that something was wrong was on 2nd March when I was at work and a colleague mentioned I looked flushed. When I got home, I took my temperature and was shocked to see it was 39.1 Celsius. I contacted 111 and was advised my GP would have to see me that evening. The GP asked some questions prior to me attending, mainly regarding travel to China or Italy. He checked my throat, ears, urine and nothing out of the ordinary was evident. He suggested I could be brewing something and to see how I felt over the next few days. Well I continued to feel fine so carried on as normal.

All was good until 14th March when I though I was developing a sore throat, no high temperature until the following evening (when I was preparing for work the following day) I took my temperature which was 38.7 Celsius. I was not feeling particularly unwell but by this stage there was a clear instruction not to go to work with a high temperature.

This was just the beginning, the next 10 days were spent bedridden with an unrelenting fever, no energy to do anything, unable to eat or drink due to diarrhoea plus having no appetite (even the thought of swallowing paracetamol made me feel nauseous). The only thing I could keep down was small sips of water. I remember it took me 1.5 hours to work up the energy to get out of bed to go to the bathroom. As a measure of how little energy I had, I was unable to shower or bathe for the 10 days. I did develop the dry cough but not until day 6.

I did contact 111 and was called back after 36 hours, to be told I wasn’t ill enough for hospital but if I reached a point of being unable to breathe to phone 999. It was a frightening time, feeling the most unwell I’d ever felt in my life but no option to attend the GP, who stayed in contact with me by email. I got out of bed one morning and everything went black, this was probably the lowest and worst point of the virus.

However, after 2 weeks I felt I was starting to recover and another week at home made me feel well enough to return to work. I should mention I continued to take my warfarin throughout the 3 weeks and when I was able to return to the Anticoagulation Clinic had an unmeasurable INR and required Vitamin K to urgently reverse the warfarin. In retrospect I was lucky to be taking warfarin as the accounts of sticky blood with COVID-19 are of great concern if you are already diagnosed with Antiphospholipid Syndrome.

Repercussions of the illness have been fatigue meaning I sometimes got into bed as soon as I got home from work and afternoon naps becoming a regular feature of my weekends. The other alarming side-effect was hair loss, which started about 3 months post COVID-19. I am happy to say both are now lessening.

Medical comment
COVID-19 can present in three forms- mild- when the patient is unwell but does not have shortness of breathe; moderate- when patients gets SOB and low on oxygen in the blood due to pneumonia caused by the virus; and lastly severe –when the patient requires support from mechanical ventilation to breathe.
This is a description of “mild” COVID-19 although it was far from mild as far as symptoms are concerned.

It is really important to note that the risk of having COVID-19 and the risk of getting COVID-19 pneumonia are not increased in those with previous blood clots. Blood does get very sticky in those who have COVID-19 pneumonia, but not in those with mild COVID-19.

There is no evidence that those with recognised conditions such as antiphospholipid syndrome will get more blood clots than someone who does not have antiphospholipid syndrome, but obviously it is important to keep taking anticoagulation.

Taking warfarin, one needs to make sure that the intake of vitamin K is the same every day (it is mainly in green food in the British diet) so not eating when ill, as in this description will lead to a very high INR.

This very good description of having mild COVID-19 occurred in March when there was little testing. Now one would automatically go for COVID-19 PCR testing with the first symptoms.


Becky’s account of blood clots in a time of COVID-19

[Horse Hounds July 2020]

A rider who spent three weeks in hospital with severe blood clots has warned others to be aware of the life-threatening condition.

Becky Read suffered deep vein thrombosis and pulmonary embolism some six weeks ago and was lucky she did not lose her leg — or her life.

Becky told H&H she first noticed issues a fortnight before she was admitted to hospital; she had been training for a half-marathon but found herself very short of breath on short runs. She was also experiencing muscle pains.

“A couple of days later, I woke up in the night, in the worst pain I’d ever experienced,” she said. “It was as if someone was stabbing me, on the whole right side of my torso; I was screaming in pain.”

Becky called 111 and was told Covid-19 can cause muscle pains so she had a test, which was negative. She and her partner were told to self-isolate in case the test was inaccurate, but she experienced more severe muscle pains, nausea, confusion and light-headedness over the next few days.

Read Full Story [Horse & Hounds]