Antiphospholipid syndrome (APS)

What is antiphospholipid syndrome (APS)?

Antiphospholipid syndrome is often referred to as APS or sticky blood syndrome.

APS is a major cause of strokes in people under the age of 50. Unfortunately, it’s often only diagnosed after a person has had a number of miscarriages, or blood clots in their arteries, veins or brain.

The condition can also be called Hughes Syndrome, after a doctor who researched and published information on the condition in the 1980s. Although it was first discovered as a secondary condition in people with lupus, APS is also a condition in its own right – this is called primary APS.


Before being diagnosed with APS and given treatment, people can have a number of blood clots in their arteries and veins. This is known as thrombosis. You may have had a stroke at a relatively young age or been told you have a low platelet count, heart or kidney problem.

Women with the condition can have several miscarriages and stillbirths. APS can also cause:

  • high blood pressure in pregnancy - known as pre-eclampsia
  • early births
  • small babies.

Many people with APS have no symptoms and feel relatively fit and well. Some other people with APS, particularly those who also have lupus, get a rash, joint pains, migraines and become very tired, even when they aren’t pregnant or don’t have blood clots.

It is not unusual for people with APS to have periods of tiredness, forgetfulness, confusion and anxiety.

Sometimes you may find it difficult to think of the words you want to say. In its extreme you may find dramatic gaps in your memory. You may forget how to do simple tasks, completely miss pre-planned events or even forget how to get home.

It’s important to get an early diagnosis and begin the right drug treatment as soon as possible to prevent future thromboses or miscarriages. It will also help you understand and get more help for the symptoms you are experiencing.

Blood clots

Though people with APS have a higher risk of thrombosis than others, this doesn’t mean they’ll get blood clots all the time. You may go for many years without getting any.

There are warning signs that you may be developing a blood clot. These include:

  • sudden pain, warmth, and swelling in one leg or arm
  • shortness of breath
  • chest pain
  • coughing up blood-streaked mucus
  • numbness, paralysis or weakness in your face or limbs
  • slurred speech
  • problems with your vision.

Contact your GP if you’re experiencing any of these symptoms.

Where do you get blood clots?


This causes pain and swelling, usually in the calf. This is called deep vein thrombosis or DVT and can sometimes lead to severe chest pain or shortness of breath, or both. If this happens, a piece of the clot may have broken away and travelled to the lung, causing a pulmonary embolism.


This can cause high blood pressure, strokes or heart attacks.

The brain

This can be associated with memory loss, migraines, slurred speech, epileptic fits or sight problems.

On very rare occasions, numerous clots form in various parts of the body at the same time, which can damage several organs at once. This is called catastrophic APS. It’s thought to be triggered by infection, trauma, medication or surgery.

If you are diagnosed with catastrophic APS, you would need to be treated in hospital, where you would have access to rheumatology and haematology teams.


Pregnant women with APS are at greater risk of miscarriage throughout their pregnancy. But the risk is particularly high during the second trimester, between three and six months. Women with APS are also five times more likely to have a stillbirth.

APS is one of the most significant causes of repeated miscarriage, but once you have been diagnosed, treatment can reduce your risk in future pregnancies.

Because it affects both the placenta and womb, APS can also cause other complications in pregnancy. These include:

  • raised blood pressure
  • hypertension
  • pre-eclampsia
  • small babies
  • a need for an early delivery.

Problems caused by APS

Heart problems

The heart valves can thicken and may fail to work, or the arteries may narrow because their walls get thicker, leading to angina, chest pain or heart attacks.

Kidney problems

APS can cause narrowing of the blood vessels, including those serving the kidneys, resulting in high blood pressure and poor kidney function.


Testing for antiphospholipid antibodies is becoming routine in infertility clinics.

Skin problems

Some people develop a blotchy rash, with a lacy pattern, often seen on the knees or arms and wrists, this is called livedo reticularis.

Low platelet count

Platelets are small cells in the blood, which play a part in controlling bleeding. Some people with APS have low platelet levels.

There are often no symptoms, although people with very low platelet counts may bruise easily or experience excessive bleeding.


APS is an autoimmune condition. This means your immune system, which usually protects you from disease and infection, is attacking healthy parts of your body with harmful antibodies.

In APS, antiphospholipid antibodies (aPL) change the blood. They attach themselves to proteins in fats, which affect the blood cells.

This makes the cells stick together in clumps which can block the flow of blood through arteries and veins. This can happen anywhere in the body, including the brain.

In pregnant women, these abnormal antiphospholipid antibodies can also affect the cells of the womb and the placenta, reducing blood flow to the baby. This can slow down the baby’s growth and increase the risk of miscarriage and stillbirth.


People who have thrombosis or recurrent miscarriages should be routinely tested for APS. If you’ve had either of these problems, especially if they’ve happened more than once, you should talk to your doctor about whether you need testing.

Your doctor will want to talk about your medical history. They would expect to see that you have experienced at least one of the following:

  • Blood clots
  • At least one miscarriage and blood clots
  • Three or more early miscarriages and/or one late miscarriage (second trimester).

They will also discuss any other problems you seem to be having, to see whether there could be any other reason for these issues. Miscarriages, strokes, heart problems and other symptoms are not just caused by APS. There are also other things that can cause clots in your blood.

Who gets APS?

APS can be diagnosed in any age group, from infants to the elderly, but is most commonly found in people aged 20 to 50. Because of its impact during pregnancy, it appears to be more commonly diagnosed in women than men.

It’s one of the most common causes of strokes in young people. It’s estimated that one in six people who have had a stroke before the age of 40 may have APS.

Are there tests for APS?

To confirm a diagnosis of APS, you will need to have three types of blood test. It’s important to have more than one of these types of test to get a proper diagnosis. This is because each test looks for antiphospholipid antibodies differently. Doing only one of these tests could miss the diagnosis.

You will usually have each test twice, 12 weeks apart. Your GP may carry out some of these tests, but at least one of them will be done as an outpatient in hospital.

The tests for APS are:

  • the anticardiolipin test
  • the lupus anticoagulant test
  • the anti-beta-2-glycoprotein 1 test.

Each test can tell whether abnormal antiphospholipid antibodies are present in your blood. But, the results can vary because the tests are looking for different things. It is possible to test positive in one, two or all three.

What do these tests show?

The lupus anticoagulant test gives a positive or negative result. It tells you whether antiphospholipid antibodies are present or not, but not how high the level is.

Despite its name, the lupus anticoagulant test only looks for APS. If you test positive for the lupus anticoagulant, it doesn’t mean you have lupus (SLE). It also doesn’t mean you have a blood thinner in your blood.

The results of the anti-cardiolipin and anti-beta-2-glycoprotein 1 tests are given as numbers. The higher the number, the higher the number of antiphospholipid antibodies in your blood.

What do these results mean?

The tests need to be carried out twice, 12 weeks apart, because the levels of antiphospholipid antibodies in your blood change and can increase when you have an infection.

If you only have one positive test and it becomes negative 12 weeks later, you probably don’t have APS.

It’s generally accepted that to have a confirmed diagnosis of APS, at least one test must be positive on at least two occasions. It’s also expected that you would have a history of blood clots and/or miscarriages.

People who are positive in all three tests have a higher risk of developing clots than those who are positive in one or two. The higher the level of antibodies found in the anticardiolipin or anti-beta-2-glycoprotein I tests, the greater your risk of developing blood clots.

Depending on their diagnosis, your doctor may refer you to a doctor specialising in immune conditions, known as a rheumatologist, or a doctor specialising in conditions affecting the blood, known as a haematologist.

What does it mean if you’re aPL-positive but don’t have APS?

Some people can find out they are positive for the antiphospholipid antibodies without having had any of the symptoms of APS. They may have been tested for antiphospholipid antibodies as part of their diagnosis for another condition.

About 20 to 30% of these people test positive for antiphospholipid antibodies, but don’t have APS. They are described as being aPL-positive and can usually carry on without having any symptoms of APS.

This is why doctors look for a history of blood clots and miscarriages before making a diagnosis of APS. However, they need to consider whether an aPL-positive person without symptoms could get APS in the future.

There’s no foolproof way of doing this, but they look at a number of factors, such as:

  • how high your antiphospholipid antibodies level is
  • how many of the three tests are positive
  • whether you have other risk factors for thrombosis
  • whether you have other typical symptoms of APS, such as migraines.


Being diagnosed with APS means you are halfway to reducing the impact the condition has on your life. You no longer have the uncertainty of what is causing you to have miscarriages, blood clots, problems with your heart or kidneys, or other serious illnesses.

Many women who in the past wouldn’t have been able to have babies are now able to safely give birth, because of treatment.

You will always have the condition and will need to be monitored by your healthcare team, but there are treatments and things you can do yourself to reduce its risks.


Treatment with anticoagulant drugs, which thin the blood, can help prevent blood clots and miscarriages.

The most commonly used drugs are low-dose aspirin, warfarin and heparin.

Blood-thinning drugs

Often, to reduce the risks of APS, you will be given a type of anticoagulant drug to thin your blood. The type of treatment you receive will depend on your symptoms.

If you’re aPL-positive or have APS, but have no history of clotting

If you have no history of blood clots, but have been diagnosed with APS after miscarriages, or have been found to be aPL-positive during blood tests for another condition, you’ll probably be prescribed low-dose aspirin. This can reduce your chance of getting blood clots or miscarrying in the future.

Your doctor will probably recommend a daily low dose of aspirin, often around 75mg. This isn’t guaranteed to prevent blood clots, but it can make the blood less sticky.

If you have other factors that increase your risk, such as a family history of clots, or if you suffer from typical APS symptoms, such as migraines, your specialist may recommend that you take warfarin instead of aspirin.

If you have APS and a history of clotting

To lower your risk of having more blood clots, you’re likely to be given warfarin tablets. You’ll need to have regular blood tests, called international normalisation ratio tests, or INR for short, which check how long your blood takes to clot.

The INR blood tests may just be a finger-prick test, or they may need to be sent off to a lab before you get the results. The longer it takes your blood to clot, the higher your INR result. Your INR result tells doctors what effect warfarin is having on your blood and helps them work out what dose you should be taking.

Your warfarin dose needs to be closely monitored, because the most serious side-effect of this treatment is the risk of excessive bleeding. Your dose can be adjusted, depending on your INR result.

Warfarin can interact with a number of drugs and foods such as:

  • alcohol
  • cranberry, pomegranate, and grapefruit juice
  • broccoli
  • steroid treatments
  • antibiotics
  • some painkillers.

It’s important that you’re aware of this and take steps to make sure your other medications or diet won’t affect the results of the blood tests.

If you’re trying for a family after miscarriages, but haven’t had blood clots

Your APS treatment will be based on two things:

  1. What treatment you’ll need to prevent another miscarriage.
  2. Whether you’ll need treatment to prevent clots after the birth.

Women with APS and a history of pregnancy complications are usually prescribed low-dose aspirin and daily heparin injections during pregnancy, to reduce the risk of miscarriage.

If you’re taking warfarin and want to start a family or if you become pregnant, you must talk to your doctor as soon possible. Warfarin could be harmful to your baby, so you’ll be swapped to heparin and aspirin treatment by week six of pregnancy.

Most APS specialists also work in maternity clinics. Ask to be referred to one, ideally before you become pregnant. They can make you aware of all the relevant issues that could affect you and your baby throughout your pregnancy.

If you’ve had miscarriages because of APS, your risk of clots could increase when you’re not pregnant, so you may be advised to take low-dose aspirin afterwards.

Advances in the understanding and treatment of APS mean more women with the condition have had successful pregnancies. However, even with treatment, complications can sometimes happen towards the end of the pregnancy.

With close monitoring of the pregnancy, there’s now a very good chance your baby will have no long-term problems.

Direct-acting oral anti-coagulants, known as DOACs, have been used to treat some people with APS in the past. However, they are now thought to increase your chances of developing blood clots that can interfere with organs such as your lungs and brain. DOACs are not recommended for treating APS, particularly if you’ve tested positive in all three blood tests.

DOACs not recommended for treating APS include:

  • apixaban – brand name Eliquis
  • dabigatran etexilate – brand name Pradaxa
  • edoxaban – brand name Lixiana
  • rivaroxaban – brand name Xarelto

Managing symptoms

It’s important to understand the symptoms and impact of APS, and to know when to ask for help. You should be able to contact your specialist team for advice when you need it.

If you’re taking medication such as warfarin, you need to avoid contact sports and activities that could cause you to hurt yourself.

Blood-thinning drugs can make you bruise very easily and badly. Because they increase the time it takes for your blood to clot, it can be difficult to stop the bleeding if you cut yourself.

If you’re pregnant, you also need to let your specialist obstetric consultant know about any changes to your health.

Lowering the risk of blood clots

There are several drugs that can help prevent blood clots developing. There are also things you can do to reduce your risk of clots in your blood, including:

Stopping smoking

Smoking thickens the blood and hardens and narrows the arteries which can increase your risk of getting blood clots. It also raises your blood pressure and heart rate, increasing your risk of heart disease, strokes and permanent damage to the veins and arteries. If you can stop it will help. Your doctor can help you find the best way to quit.

Be alcohol aware

Alcohol has an anticoagulant effect, meaning it can make your blood thinner, and can slow down your liver’s ability to process warfarin, which affects your INR levels. Government guidelines recommend you shouldn’t drink more than 14 units, throughout the week. However, because of the effect it has on your INR levels your rheumatologist may recommend you drink less than this.

Stay hydrated

Drink plenty of fluids, particularly water, so you don’t become dehydrated.

Avoid oestrogen contraceptives and HRT

Try to avoid contraceptives or hormone replacement therapy (HRT) containing oestrogen, as it can increase your risk of blood clots. Ask your doctor about other types of contraception, such as the progestogen-only pill or injection, having a Mirena Coil fitted or barrier methods. HRT skin patches are considered safer than tablets because they don’t make the blood as sticky and carry less risk of causing clots in the veins. There are also non-hormonal treatments that can help with some symptoms, such as hot flushes.

Move around

Try not to sit in one position for too long. For example, if you’re taking a long bus journey, or a long-haul flight try to plan ahead and book either an aisle seat or one with extra leg room, so you can stretch and move your legs. If you’re travelling in a car you also need to make regular stops to stretch your legs. Some people recommend wearing elasticated stockings during a long journey to reduce the risk of clots building up in the lower legs. Ask your specialist whether this would be good for you. Even when you’re sat at your desk or at home try to get up and move around as frequently as possible.

Other conditions

Pregnancy increases your risk of blood clots, so you should be closely monitored and will be given drug treatment to help limit complications. Conditions, such as diabetes, high blood pressure or cholesterol can increase your risk too, try to keep on top of them by having regular check-ups. If you have a family history of blood clots, miscarriages or other autoimmune conditions, such as lupus or thyroid problems, that could also put you at greater risk. Some people can also develop blood clots if they have an infection, such as a sore throat. These are all things your doctor can advise you on.


Though there aren’t any exercises that can help specifically with the condition, regular exercise keeps you fit, keeps your heart healthy and helps prevent blood clots.

Yoga, walking, swimming and Tai Chi are good low-impact types of exercise that can help you physically and mentally. Tai Chi also helps with any problems you have with your balance.

Speak to a member of your healthcare team before you make any changes to your regular exercise routine.


You should aim to routinely stick to a healthy, balanced diet, containing a good mix of carbohydrates, proteins, fruit, vegetables and low-fat dairy products.

It’s important to make sure your diet has food containing vitamin K in it. Vitamin K affects your blood’s ability to clot and can affect how warfarin works. Too little vitamin K in your diet can increase your INR levels, while too much decreases them. Vitamin K is mostly found in leafy green vegetables, such as:

  • spinach
  • kale
  • broccoli
  • asparagus
  • lettuce.

It can also be found in:

  • chickpeas
  • liver
  • egg yolks
  • wholegrain cereals
  • mature cheese and blue cheese
  • avocado
  • olive oil.

While it’s important to make sure you have these vegetables in your diet, you need to balance the amount you eat each day. Too much could increase your risk of clotting and affect your INR levels, but too little is unhealthy. Speak to your doctor about the amount of vitamin K in your diet and how it could affect your warfarin dose.

Some herbs and spices also affect your blood flow and the time it takes to clot.

The anticoagulant effect of warfarin can also be affected by:

  • cranberry juice
  • grapefruit juice
  • pomegranate juice
  • garlic
  • dong quai
  • danshen (red sage)
  • devil’s claw
  • Korean ginseng
  • green tea.

A member of your healthcare team should be able to advise you on a good healthy diet that won’t interfere with your treatment.

Increasing the amount of essential fatty acids in your diet, particularly omega-3 fatty acids, could help reduce the risk of clots. These are found in oily fish. However, there are no clinical trials to support this.

If you’re trying for a baby, it may be best to avoid fish liver oil supplements, as they contain large amounts of vitamin A, which can be harmful.

Complementary and alternative treatments

At present, there are no complementary medicines that have been shown to help with APS.

Besides vitamin K, supplements such as vitamin C, vitamin E, coenzyme Q10 and the remedies devil’s claw and St John’s wort can also alter the body’s reaction to warfarin.

Speak to your doctor, pharmacist or healthcare team before trying any new treatment.


APS can make you feel very tired, both physically and mentally, but there are ways you can manage this fatigue.

A healthy balanced diet and regular exercise routine will help with your general physical health, plus your mood and stress levels. Sticking to a regular night-time routine can also improve the quality and quantity of sleep you get.

Try not to do too much all at once - plan your chores, tasks or jobs around how much energy they will use. Pace yourself and try not to ‘boom and bust’. This is when you try to get as much done as possible in a short time, before you run out of energy.

Try to balance light jobs with ones that use more energy, with rest in between.

Stress and memory problems

People with APS can experience episodes of memory loss, anxiety and confusion.

Making your days and activities more routine can help reduce the impact of these periods, as can memory aids and learning relaxation techniques.

Puzzles, memory boards, calendars and socialising can all help reduce the effects of stress and keep your mind active, as well as improving your memory.

It can help to talk to friends and family about your condition and explain how it affects you. Some people also find that cognitive behavioural therapy (CBT) helps them manage some of the problems that are causing stress, poor sleep and low mood.

Your doctor can talk to you about CBT. They should also be able to put you in touch with a local support group for people with long-term conditions – many have similar impacts on people’s lives.

You can also find help and advice through the community at the charity APS Support UK.

Working with APS

If you work, your symptoms may have already caused problems for you. You may have had to miss work because of migraines, hospital treatment or doctor’s appointments. You may have been questioning your abilities because of becoming forgetful or tired.

With a diagnosis, you are in a much better position to explain to your employer and colleagues how your condition affects your work routine.

With the help of your doctor and union representative, you and your employer can find ways to reduce the stress and fatigue you may have at work.

Explaining your condition can also remove any insecurities you may feel and stop any future doubt or misunderstandings.

Research and new developments

In 1999, Versus Arthritis discovered that giving pregnant women heparin injections reduces the chance of miscarriages and blood clots. This led the UK Royal College of Obstetricians and Gynaecologists (RCOG) to change its guidelines surrounding the treatment of women who had experienced recurrent miscarriages.

This research has given many women with APS, who couldn’t have children before, the chance to have successful pregnancies.

Versus Arthritis is currently researching why people with conditions like APS are more prone to vascular disease. This is a condition that affects blood vessels and can lead to heart attacks and strokes.

Our research aims to help reduce the risk of people with APS having serious complications. The aim is to prevent them, by developing new drug treatments to ‘switch off’ harmful signals and ‘switch on’ protective ones within the lining of the blood vessels.