Educational information, not medical advice — ask your doctor or midwife.
Sujil is a dried leech. It is the whole body of the leech Hirudo nipponia, dried and used as a single drug in Korean medicine. In English it is simply called leech.
Healers use it to move what the old texts call stuck blood. In plain words, that means fixed sharp pain, hard lumps, and painful or missed periods. It was never a daily tonic.
Here is the short verdict. Its place in the old texts is strong, but good human trials of the dried drug are lacking. Long use in tradition is not proof that a thing works.
Leech products can thin the blood. So the safety notes below matter more than any claim made for it.
No one has shown how sujil acts in the body when you swallow it.
Live leeches make hirudin, a protein that stops blood from clotting. That is why a leech bite keeps bleeding. Sujil is dried, and drying breaks much of that protein down.
Hirudin is a protein, and your gut breaks proteins apart. So a swallowed dose may act far less than a leech bite does. Treat any story about how it works as a theory, not a fact.
Korean texts explain it in their own terms. They say sujil breaks up stuck blood and softens lumps. That is a traditional idea, not a lab result.
Sujil comes as the dried, whole leech body. Most often it is ground into a fine powder.
You may meet it as a small dose of plain powder, boiled in water with other herbs, or pressed into pills. It is rarely used on its own. Korean formulas usually pair it with other herbs.
Live leech therapy is a different treatment. There, a living leech is placed on the skin. Do not mix the two up.
There is no standard strength on the label. Purity and dose vary by supplier.
Sujil is an old drug. Chinese herb books listed leech around 2,000 years ago. Korean medicine took it up from there.
It appears in the Donguibogam, the great Korean medical work of 1613. Doctors used it after a fall or blow, and for period pain with clots.
The old texts also warned against it in pregnancy. That warning still holds today.
Some reactions to sujil need urgent care. Call your local emergency number or go to an emergency department straight away — do not wait to see whether it passes.
Stop taking sujil and get urgent medical help if you notice bleeding that will not stop, blood in your urine, black or bloody stools, coughing or vomiting blood, a sudden severe headache, or new weakness or confusion.
Call emergency services if you have trouble breathing, swelling of the face, lips or throat, or a widespread rash. These can be signs of a severe allergic reaction.
See your doctor within a few days if you bruise more easily than usual, your periods become much heavier, or you feel dizzy and tired. Tell every doctor, dentist and pharmacist that you are taking a leech product.
Evidence grades and traditional-use labels are explained in our methodology. Nothing here is medical advice.
Reviewed by the HealisticMD editorial team How we grade evidence →
The published evidence for sujil is weak or absent. That usually means no controlled trial has tested it, not that a trial found it ineffective — the two are different, and we grade only what has been published.
What it is typically used for, usual dose, cautions, and the study behind it where real trial data exists.
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