Why some hormone pills might cause blood clots
Esterified estrogens and conjugated equine estrogens and the risk of venous thrombosis.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Esterified estrogen showed no increased risk of blood clots — even though it’s also an oral estrogen.
Most people assume all oral estrogens carry the same clotting risk. This study breaks that assumption — suggesting the chemical source (horse urine vs. plant-based) may matter more than the delivery method.
Practical Takeaways
If you're on hormone therapy, ask your doctor what type of estrogen you're taking — and whether esterified estrogen might be a safer alternative.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
Surprising Findings
Esterified estrogen showed no increased risk of blood clots — even though it’s also an oral estrogen.
Most people assume all oral estrogens carry the same clotting risk. This study breaks that assumption — suggesting the chemical source (horse urine vs. plant-based) may matter more than the delivery method.
Practical Takeaways
If you're on hormone therapy, ask your doctor what type of estrogen you're taking — and whether esterified estrogen might be a safer alternative.
Publication
Journal
JAMA
Year
2004
Authors
N. Smith, S. Heckbert, R. Lemaitre, A. Reiner, T. Lumley, N. Weiss, E. Larson, F. Rosendaal, B. Psaty
Related Content
Claims (6)
Women who are going through or have passed menopause and are taking a specific type of hormone pill called conjugated equine estrogen are 65% more likely to have their first blood clot in a vein than women who aren’t taking any hormones.
Women who are going through or have passed menopause and are taking a specific type of hormone pill called esterified estrogen aren’t more likely to get a dangerous blood clot for the first time than women who aren’t taking any hormones.
Women who take a type of hormone therapy called conjugated equine estrogen are 78% more likely to develop blood clots in their veins than women who take a different type called esterified estrogen.
Women who take higher doses of this hormone medicine called conjugated equine estrogen are more likely to develop blood clots in their veins.
Women who take both estrogen and progestin together have a 60% higher chance of developing blood clots in their veins than women who take estrogen alone.