COVID-19: your guide to health risks after infection

16th July, 2022 • 13 min read

As we continue to live with

, scientists are learning more about the ways the virus affects our health – and the longer-term health issues it can cause.

By now, you’ll be aware of

long COVID
– where symptoms such as tiredness, shortness of breath, muscle aches and loss of smell can last for weeks or months after you’re infected. 1 study found that women are twice as likely to have long COVID symptoms than men, even if they had only a mild infection. Read more about the reasons why

But now research suggests having COVID-19 puts you at a greater risk of 3 serious, potentially life-threatening health issues. Studies indicate COVID-19 can increase your chances of having diabetes, blood clots, and serious complications from surgery.

Find out more about these health issues that could be caused by COVID-19 and the risk to your health. Read on for the latest research, the symptoms to look out for – and why delaying surgery after having COVID-19 could save your life.

Diabetes and COVID-19

Up to a year after having COVID-19, your chances of being diagnosed with

type 2 diabetes
are raised. The risk is higher in the first 3 months after an infection, and if you’re overweight or obese (check out the healthy weight for your height
), or you have an underlying health condition. Researchers say it’s important to be aware of the symptoms of type 2 diabetes and see a doctor if you spot them.

The essentials

  • you’re around 40% more likely to be diagnosed with diabetes up to a year after having COVID-19
  • your risk of developing type 2 diabetes is highest up to 3 months after COVID-19, but can return to normal after 12 weeks. Your risk is higher if you have an underlying health issue or are overweight
  • your risk of developing type 2 diabetes after COVID-19 is doubled if you have a high
    body mass index (BMI)
  • if you were severely ill or went to hospital with COVID-19 your risk is 3 times higher than people who did not have COVID-19

What are the symptoms of type 2 diabetes?

If you have

type 2 diabetes
your body doesn’t make enough insulin or doesn’t react to insulin and your blood sugar levels get too high. Symptoms to look out for are:

  • feeling very thirsty
  • peeing more often than usual, particularly at night
  • feeling very tired
  • losing weight for no obvious reason
  • itching on your penis or vagina, or you keep getting thrush
  • cuts or wounds that heal slowly
  • blurry vision

Read more about the

symptoms of type 2 diabetes

When to see your doctor

Book an appointment with your doctor if you start to have some of the symptoms above. You may be more at risk of type 2 diabetes if:

  • you’re over 40 and white, or over 25 and of South Asian, African-Caribbean or Black African descent
  • you’re overweight, especially if you have excess fat around your tummy
  • have a close relative with type 2 diabetes
  • have high blood pressure
  • you smoke

How is type 2 diabetes diagnosed?

To find out if you have type 2 diabetes, you’ll need a blood test that checks your blood sugar levels. This is quick and straightforward and can be arranged through your doctor.

You can read more about the common types of blood glucose tests in our

blood tests article

What are the treatments?

In some cases, type 2 diabetes can be managed with lifestyle changes, around your diet, weight and the amount of exercise you do.

You may need medication, usually tablets, to control your blood sugar levels.

Read more about

treating type 2 diabetes

The studies in detail

  • a study by King’s College Hospital published in the BMJ found people who had COVID-19 were more at risk of developing type 2 diabetes in the first 3 months after being infected. Researchers looked at the health records of 428,650 COVID-19 patients and a control group who hadn’t had COVID-19. Data take-out: the risk was highest in the first 4 weeks after infection, but it remained raised for up to 12 weeks before declining. The researchers didn’t find any evidence that the risk was increased after this. The COVID patients were more likely to be overweight than the control group, and also on average had more pre-existing health conditions. The researchers concluded that the rise in cases of diabetes may not entirely be linked to COVID-19, but due to pre-existing risk factors for type 2 diabetes
  • a US study, published in The Lancet Diabetes and Endocrinology journal, looked at more than 180,000 veterans who’d had COVID-19, to see if they had an increased risk of developing diabetes. It compared medical data from 3 groups: those who tested positive COVID-19 between March 2020 and September 2021, those who hadn’t, and a pre-pandemic group. Data take-out: it found an increased risk, especially in people who were hospitalised. It’s worth noting that many people in this study were already overweight and had high blood pressure, both of which are risk factors for type 2 diabetes. Researchers recommended that people who’ve had COVID-19 should be considered for screening for diabetes
  • a German study, published in Diabetologia, looked at diabetes diagnosed after mild doses of COVID-19. The researchers number-crunched data from more than 1,000 doctor’s practices across Germany, looking at the number of cases of diabetes diagnosed after infection with COVID-19, compared with a control group of people with acute upper respiratory tract infections (AURI). Data take-out: although the study found the risk of getting type 2 diabetes was 28% higher in the COVID-19 group, it concluded that diabetes is unlikely to be a problem for most people who had mild COVID-19. But researchers recommended people who’ve had COVID-19 be aware of the symptoms of type 2 diabetes and see a doctor if they start to have them

Blood clots and COVID-19

A large study from Sweden has found that there’s an increased danger of having a blood clot up to 6 months after having COVID-19. Plus, a new study from King’s College London also found an increased risk for cardiovascular disease, including a higher risk of clots and DVT.

The essentials

  • you have an increased risk of DVT for up to 3 months after COVID-19, pulmonary embolism for up to 6 months, and bleeding for up to 2 months
  • the risks are higher if you have underlying health conditions, had a severe case of COVID-19, particularly if you were hospitalised
  • mild COVID-19 was associated with an increased risk of DVT and pulmonary embolism, but not bleeding
  • severe COVID-19 means you are six times more likely to have a cardiovascular diagnosis. This includes an 11-fold increase in pulmonary embolism, a 6-fold increase in atrial arrhythmias, and a five-fold increase in deep vein thrombosis

Dr Nathan Cohen says: “although being bed bound is a known risk factor for getting a clot, there is evidence that those who have COVID-19 are at a higher risk than other people who are in hospital or intensive care units. There are a number of theories as to why this is the case. One is that the body’s immune system is activated to fight COVID-19 and this can make clots more likely to form. Another theory is that COVID-19 actually triggers the blood to clot to give it a survival advantage. However, this needs to be further investigated.”

What are the symptoms of blood clots?

Your blood contains natural clotting agents, which stop you bleeding too much if you cut yourself. But sometimes this system goes wrong, and you can get a blood clot in an artery or vein when there’s no bleeding.

When to see your doctor

The symptoms of a blood clot vary depending on the type of clot, but go to the emergency department if you have symptoms of a:


This is a blood clot that stays in one place, usually a vein in your leg, and it needs immediate medical attention. Symptoms include:

  • pain, swelling and tenderness in 1 of your legs (usually in the calf)
  • a heavy ache in the area
  • warm skin
  • red skin, especially on the back of your leg, below your knee


This is a clot that moves through your body and can cut off the blood supply to an organ. It often starts as a DVT that becomes dislodged and moves. If blood can’t reach your brain, it can cause a

, while a pulmonary embolism is when the blood is cut off from your lungs. Symptoms to be aware of include:

  • for stroke – drooping face, weakness or numbness in one arm, slurred speech, being unable to talk or understand what’s happening
  • for pulmonary embolism – a sharp or stabbing pain in your chest, shortness of breath, coughing up blood, feeling faint or passing out

You’re more likely to get a blood clot if:

  • you’re
  • you’re pregnant
  • you smoke
  • you’ve had a blood clot before, or someone in your family has had a blood clot
  • you have heart disease or cancer

How are they treated?

Blood cuts need to be treated immediately. Blood thinning medication, such as warfarin, heparin or rivaroxaban, are given to dissolve the obstruction and stop further clotting. These blood thinners are often used as follow-up treatment to prevent new clots forming.

Sometimes you’ll need surgery, where an operation called an embolectomy is carried out to remove the blockage.

Alternatively, you may be able to take medication, such as warfarin, heparin or a low-dose aspirin, to dissolve the clot and stop further clotting.

Read more about

DVT treatment
treating pulmonary embolism
, and
blood-thinning medication for blood clot

The studies in detail

  • a Swedish study, published in the BMJ in April 2022, set out to find the risk of a blood clot in the leg (
    deep vein thrombosis or DVT
    or lung (
    pulmonary embolism
    ) after having COVID-19, as well as the risk of bleeding. The researchers looked at national registries in Sweden for more than 1 million people diagnosed with COVID-19 (and more than 4 million control participants who weren’t). The average age was 40, while 49% were men and 51% women. Data take-out: the findings suggest that covid-19 is a risk factor for deep vein thrombosis, pulmonary embolism, and bleeding. The rates were higher for people who had severe COVID-19 and those who had an infection in the first wave of the pandemic
  • a study by King’s College Hospital published in the BMJ found people who had COVID-19 were more at risk of developing cardiovascular disease in the first 4 weeks after being infected. Researchers looked at the health records of 428,650 COVID-19 patients and a control group who hadn’t had COVID-19. Data take-out: the risk of a new heart disease diagnosis started to drop 5 weeks after infection and returned to baseline levels or below from 12 weeks to 1 year. Researchers concluded that people who had COVID-19 but didn’t have pre-existing cardiovascular disease symptoms didn’t seem to be at long-term risk from developing this health issue

Surgery and COVID-19

Studies from the US and UK have shown that there’s an increased risk of dying if you have surgery too soon after having COVID-19.

The essentials

  • the biggest risk of complications – such as pneumonia or a blood clot – was seen in the group who had surgery 0 to 4 weeks after infection
  • surgery 4 to 8 weeks after infection still had an increased risk of pneumonia
  • having COVID-19 gives you a much higher risk of death after surgery – 21.4%, compared with 0.8%
  • among those having planned surgery, 7.1% of the people with COVID-19 died, compared with 0.1% of non-COVID patients
  • among those having emergency surgery, 25.1% of the people who had COVID-19 died, compared with 3.4% of patients without COVID-19

The studies in detail

  • the UK study, published in the British Journal of Anaesthesia, looked at the chances of death from having a planned and emergency surgery with COVID-19. Researchers looked at the records of more than 2.5 million patients having surgery in NHS hospitals in England from January 2020 to February 2021 – and more than 28,000 had had COVID-19. Data take-out: it found that mortality rates were higher in those people who had COVID-19 for both planned and emergency surgery
  • the US study, published in Annals of Surgery, of 5,000 people looked at how the length of time between having COVID-19 and having surgery affected the risk of complications. The researchers looked at 18 types of planned surgery, splitting the patients into groups depending on when they had an operation in relation to being infected with coronavirus. The 4 groups were: pre COVID-19; 0 to 4 weeks after infection; 4 to 8 weeks after infection; and 8+ weeks after infection. Data take-out: it found the biggest risks of complications were in the group who had surgery up to eight weeks after having COVID-19. Having surgery 8 or more weeks after infection wasn’t associated with an increased risk of complications

What do the medical experts say?

As a result of research, several leading medical bodies in the UK now recommend that you don’t have surgery within 7 weeks of having COVID-19, if possible.

They have also put together these recommendations:

  • if you’re having surgery you should have a pre-op
    COVID-19 vaccine
    – with 3 doses wherever possible with the last dose at least 2 weeks before surgery
  • you should let your surgical team know if you test positive for COVID-19 within 7 weeks of your planned surgery – they will discuss pros and cons so the risks and benefits of delaying surgery with you can be discussed
  • ideally don’t have planned surgery within 10 days of a diagnosis of COVID-19, as you may be infectious
  • discuss delaying surgery if you have persistent symptoms or moderate-to-severe COVID-19 as you’re likely to be at greater risk, even after 7 weeks. In these cases, delaying surgery beyond this point should be considered

If you’ve had a recent COVID-19 infection, your surgeon may consider

or regional anaesthetic instead of a
general anaesthetic

Putting the extra risk in context

Dr Nathan Cohen says: “If you have tested positive for COVID-19, it is important you discuss delaying your surgery with your surgical team as soon as possible, even if you do not have any symptoms. They will help you weigh up the urgency of your surgery, the potential implications of delaying it and the risks of the procedure going ahead. They can then book a new date that's seven weeks after the first day of your infection.”

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.