Varicose Veins Raise Blood Clot Risk During Prolonged Ramadan Fasting: What the Research Shows

Varicose Veins Raise Blood Clot Risk During Prolonged Ramadan Fasting: What the Research Shows

Medical disclaimer: This article summarises published research for informational purposes only. It is not medical advice and is not a substitute for guidance from a qualified health professional. Always consult your doctor before starting any fasting protocol, especially if you have an existing health condition or take medication.

Study at a Glance

What This Study Looked At

Ramadan fasting means no food or water from dawn to sunset for a full month — a form of prolonged daily fasting practiced by hundreds of millions of people every year. Researchers led by Joseph Caprini, creator of the widely used Caprini venous thromboembolism (VTE) risk score, wanted to know whether this pattern of daily dehydration and calorie restriction changes the risk of developing blood clots in the legs, and whether pre-existing conditions like varicose veins make that risk worse. You can read more about how intermittent fasting affects blood pressure and how Ramadan fasting compares to standard intermittent fasting protocols.

Who Was Studied

Participant profile: Adults recruited across multiple countries, including Egypt, Algeria, Tunisia, Iraq, Lebanon, Syria, and Turkey, observing Ramadan fasting. Caprini risk scores — a standard clinical tool combining age, medical history, mobility, and vascular risk factors — were calculated for each participant alongside fasting-specific factors.

How Ramadan fasting worked in this study: Participants abstained from all food and liquids, including water, from sunrise to sunset for roughly 12-16 hours depending on location and season, for the full lunar month of Ramadan. Researchers layered fasting-specific risk factors — total fasting duration, heat exposure, physical activity levels, and hydration during non-fasting hours — on top of the standard Caprini score to see which combination best predicted clotting events.

What the Researchers Found

New Blood Clot Events During Fasting

• Nearly 1 in 20 participants developed a new clotting event during the month-long fast — a meaningful signal in an otherwise healthy, community-based population.
• Elevated Caprini scores tracked closely with who actually developed a clot, supporting the score's usefulness even in a fasting-specific context.

Varicose Veins and Other Predictors

• Participants who experienced a thrombotic event had a greater prevalence of varicose veins, venous reflux, and thrombophilia than those who didn't.
• Varicose veins emerged as an independent predictor of clotting risk during prolonged fasting, consistent with their known role as a marker of impaired venous return even outside a fasting context.
• Fasting-specific factors — particularly reduced fluid intake and prolonged immobility during fasting hours — compounded the risk in people who already had venous disease.

What Did Not Change

• Participants without pre-existing varicose veins, venous reflux, or thrombophilia had a substantially lower rate of clotting events, suggesting prolonged fasting alone was not sufficient to trigger a clot in an otherwise low-risk vascular system.

What the Researchers Concluded

The researchers concluded that prolonged Ramadan fasting can unmask or worsen thrombotic risk in people who already have venous disease, and that supplementing the standard Caprini score with fasting-specific factors — fasting duration, hydration, and mobility — improved identification of people at elevated risk. They recommended targeted prevention strategies, including patient education, fluid management during non-fasting hours, and medical prophylaxis for high-risk individuals, to support safer fasting practices.

What This Means If You Fast

• Varicose veins are a legitimate reason to talk to a doctor before a prolonged fast. If you have visible varicose veins, venous reflux, or a history of clotting, this study suggests prolonged daily fasting — especially without water — carries meaningfully more risk for you than for someone without those conditions.
• Hydration during eating hours matters more than usual. Since dehydration during fasting hours was one of the compounding risk factors identified, prioritizing fluids and electrolytes once eating resumes is a practical safeguard, particularly in hot climates.
• Standard intermittent fasting (with water) is a different risk profile. This study specifically examined water-restricted Ramadan-style fasting; time-restricted eating protocols that allow water throughout the fast do not carry the same dehydration-driven clotting mechanism.
• Movement during fasting hours counts. Prolonged immobility was flagged as a contributing factor alongside dehydration — regular movement during the fasting window is a simple, low-cost mitigation.
• This is not a reason for healthy fasters to worry. The elevated risk was concentrated in people with pre-existing venous disease; participants without those risk factors had a low background rate of clotting events.
• If you notice new leg swelling, pain, or warmth during a fast, stop and seek care. These are recognized symptoms of a possible clot and warrant prompt medical evaluation rather than pushing through the fast.

Study Limitations

• Observational design with no non-fasting control group — the study cannot fully separate the effect of fasting itself from other Ramadan-season factors like heat exposure or travel.
• Sample size of 311 is modest for detecting a relatively rare event like VTE, so the 4.8% incidence estimate carries a wide margin of uncertainty.
• Full text was inaccessible via PubMed/PMC at the time of writing; figures were verified through publisher and abstract-level sources rather than the complete methods and results sections.
• Multicountry recruitment across several Middle Eastern and North African nations means climate, hydration culture, and healthcare access may not generalize to fasters in other regions.
• Conflicts of interest and funding sources were not available in the abstract-level sources reviewed.
• The study focused on Ramadan's specific water-restricted fasting pattern; findings should not be extrapolated to water-permitted intermittent fasting protocols without caution.

Source

Caprini, J. A., Fakhry, A., Nagib, S., Al-Mallah, A. H., Barsim, E. M., Farrag, M., Abouelseoud, A., Alnadi, O., Moner, M., Ghazy, Z. M., Seken, R. A., Jabr, M., Boucelma, M., & Zyada, A. (2025). Venous Thromboembolism Risk Assessment in Prolonged Fasting During Ramadan: The Global Ramadan Free Thrombosis Project. Cureus, 17(8). DOI: 10.7759/cureus.89406. View on Cureus →

Frequently Asked Questions

Does intermittent fasting cause varicose veins?

No, this study did not find that fasting causes varicose veins. It found that people who already had varicose veins were more likely to develop a blood clot during a month of prolonged, water-restricted Ramadan fasting than fasters without pre-existing venous disease.

Can fasting cause blood clots?

In this study of 311 Ramadan fasters, 4.8% developed a new venous thromboembolism event during the fasting month, and risk was concentrated in people with pre-existing varicose veins, venous reflux, or thrombophilia. Standard intermittent fasting that allows water throughout the day was not studied here and likely carries a different risk profile.

Is it safe to fast if I have varicose veins?

This study suggests people with varicose veins should talk to a doctor before undertaking a prolonged, water-restricted fast like Ramadan, since venous disease was one of the strongest predictors of a clotting event in the cohort. It does not mean fasting is unsafe for everyone with varicose veins, but it does mean extra caution and possibly medical guidance are warranted.

How common are blood clots during Ramadan fasting?

In this 311-person study, new blood clot events occurred in about 4.8% of participants over the fasting month — concentrated heavily among those with existing vascular risk factors rather than spread evenly across the whole group.

Does drinking water during a fast lower blood clot risk?

This study specifically examined Ramadan-style fasting, where water is also restricted during daylight hours. Dehydration was flagged as one of the compounding risk factors, which suggests that intermittent fasting protocols that permit water throughout the fast may carry a different, likely lower, clotting risk profile — though this wasn't directly tested here.

Related Research and Articles

• How Intermittent Fasting Affects Blood Pressure
• Ramadan Fasting vs Intermittent Fasting: What's the Difference?
• Can You Drink Water While Fasting During Ramadan?
• Electrolytes and Intermittent Fasting
• Ramadan Fasting Reduces Blood Pressure, Cholesterol, and Blood Sugar
• Intermittent Fasting in Summer Heat: Hydration Guide

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