AuthorisedTherapeutic use (Phase IV)Interventional

Evaluation of Thrombin Generation and Thrombosis Risk in Women on Hormonal Contraceptives with a Focus on Modifiable Risk Factors

Hormonal contraceptives, like the pill, are safe and effective for most women, but they can slightly increase the chance of developing a blood clot. This study aims to understand that risk more clearly. Researchers will compare blood tests from women taking various types of contraceptive pills against women who do not use any hormonal birth control. They will measure how quickly and easily the blood clots in each group. The study also examines 'modifiable' risk factors—everyday things you can change, such as body weight or smoking. By seeing how different hormones and lifestyle habits interact, researchers hope to help doctors recommend the safest birth control options tailored to each person's individual health needs.

At a glance

Status

Authorised

Phase

Therapeutic use (Phase IV)

Sponsor

University Of Debrecen

Enrolment target

350

Start

07 Oct 2026

Venous Thromboembolism Risk associated with Hormonal Contraceptives

What is this study about?

Millions of women in the UK safely use hormonal contraception every day. While these medicines are very effective, they can slightly raise the chance of developing a blood clot in a vein, known as venous thromboembolism. Clots can cause pain and swelling, and in rare cases, more serious health issues. Because different pills contain different types and amounts of hormones, they might not all carry the same level of risk.

This study investigates how various contraceptive pills change the way blood clots. Researchers will look closely at several modern and traditional hormone combinations, comparing them to each other and to women who do not take hormonal contraception at all. By testing blood samples in a laboratory, the team can measure delicate changes in how the body forms and breaks down clots.

The team is also interested in lifestyle factors that people can change, such as weight, activity levels, and smoking. They want to see whether combining certain pills with specific lifestyle factors makes a clot more or less likely.

Ultimately, this research matters because contraception is not one-size-fits-all. A clearer picture of how hormones and everyday health factors interact will help GPs and sexual health clinics give safer, more personalised birth control advice to women in the future.

Key takeaways

The study explores how different contraceptive pills affect the way blood clots.
It also looks at how lifestyle habits like smoking or weight might change this risk.
Participation involves routine blood tests and lifestyle questionnaires.
You will not be asked to start an experimental drug or change your current pill.
Findings will help doctors give more personalised, safer contraceptive advice.

Who may be eligible?

This study is open to women aged 18 and older. The researchers are looking for both women who are currently taking specific hormonal contraceptive pills and healthy women who are not using any hormonal birth control to join as a comparison group.

To take part, you must be willing to provide blood samples and answer questions about your general health and lifestyle habits, such as your smoking history and body weight.

You may not be eligible if you have certain existing medical conditions that directly affect blood clotting, if you are pregnant, or if you take other medicines that interfere with blood tests. Your study team can review your medical history to make sure taking part is suitable for you.

Could this study suit you?

Answer these quick questions to see if you may be eligible. This is a guide only — the research team makes the final call.

I am a woman aged 18 or older.
I am currently taking a hormonal contraceptive pill, OR I do not use any hormonal birth control.
I am comfortable having a routine blood sample taken from my arm.
I am willing to answer simple questions about my health and lifestyle.
I am not currently pregnant.

Answer every question to see your result.

What does participation involve?

Taking part in this study is observational, which means researchers will not ask you to start an untested experimental medicine. Instead, you will either continue using your current prescribed contraceptive pill or continue without hormonal birth control if you are in the comparison group.

You will attend a study visit at a clinic or hospital. During the visit, a nurse or researcher will take a standard blood sample from your arm and ask you some straightforward questions about your medical history, diet, exercise, and lifestyle. The visit usually takes under an hour, and you may only need to attend once or twice for blood tests, with no long-term follow-up required.

Potential risks and benefits

There is no direct medical benefit to taking part, but your involvement will help scientists better understand contraception safety for women everywhere. The physical risks are very low and mainly linked to having a blood test, which can cause brief discomfort, slight bruising, or light-headedness. Taking part is completely voluntary, and you are free to change your mind and withdraw at any time without it affecting your usual NHS medical care or access to contraception.

Locations (1)

Some site locations are approximate. We're improving this — please verify with the trial team before travelling.

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Unverified
Hungary

Common questions

Will I have to switch or stop taking my current pill?

No. The study is designed to observe the effects of pills women are already taking, or to study women who choose not to use hormonal birth control. You will not be asked to change your prescribed medicine.

What is a blood clot?

A blood clot is a gel-like clump of blood. While clotting helps stop bleeding when you have a cut, clots that form inside healthy veins can block blood flow, causing swelling, pain, or more serious complications.

What are 'modifiable' risk factors?

These are lifestyle habits or conditions that can be altered or managed, such as smoking, physical activity, and body weight, unlike fixed factors like your age or family genetics.

How much blood will be taken?

Usually just a few small vials, similar to what you would give for a routine health check at your GP surgery.

Does this study mean my birth control is unsafe?

No. Hormonal contraceptives are considered safe for the vast majority of women. Blood clots remain rare, but this study aims to make prescribing even safer and more precise.