Shangliao

What is BL31?

BL31, or Shangliao, is the top point of the sacral "eight holes" group, sitting in the first small hollow of the sacrum.

The sacrum is the flat triangular bone at the base of your spine, between the two dimples above your buttocks. It has four pairs of small openings running down it. BL31 sits in the first and highest pair, one on each side. In Chinese medicine the four pairs together are called the baliao, or eight bone-holes, and they run from BL31 down to BL34.

Tradition places BL31 on the Bladder channel and links it to the pelvic organs. Classical texts use the baliao group for period pain, irregular periods, low back and sacral ache, urinary difficulty and bowel trouble. BL31 is the point usually chosen when the complaint is felt high in the sacrum or spreads upward into the lower back.

Here is the honest verdict. There is real human research on the lower points of this group, mostly done with needles and electrical stimulation in clinics, for urinary leakage in women. There is very little research on BL31 by itself, and almost none on pressing it with a finger. Most acupressure studies anywhere are small, short and not blinded, so people know what treatment they got. That makes placebo and expectation hard to rule out.

Two things are worth saying once, clearly. A point being famous and ancient is not evidence that it works, and it is not evidence that it is safe. BL31 is a good example of why both halves matter. It is a well-taught, widely used point, and it is also a point that every teaching tradition tells practitioners to avoid during pregnancy.

Treat BL31 as a comfort measure for everyday aches, not as treatment. If a symptom is new, severe or getting worse, it needs a doctor, not a thumb.

Where is BL31 and how do you find it?

BL31 sits in the first sacral hollow, the uppermost of four small dips in the flat bone at the base of your spine, just inside and below the dimple you can feel there.

• Find the dimples. Stand or sit and run your fingers over the top of your buttocks, either side of the spine. Most people can feel or see two shallow dimples. These sit over the back tips of the pelvic bones, called the posterior superior iliac spines.
• Move inward toward the midline. From each dimple, slide your thumb about one thumb-width, roughly 2 cm, toward the spine. You are now over the sacrum itself, not the pelvic rim.
• Feel for the hollow. Press gently and move in small circles. BL31 lies in a soft dip in the bone rather than on a hard ridge. It is usually about a thumb-width to the side of the midline bony bumps of the sacrum.
• Check the level. BL31 sits roughly level with, or just a touch below, the dimple. The other three pairs, BL32, BL33 and BL34, run downward from it in a line toward the tailbone, each about a finger-width apart.
• Confirm by feel. The right spot often feels slightly tender, heavy or achy when pressed, while the bone on either side just feels hard.

BL31 is a paired point, so there is one on the left and one on the right. In traditional measurement it is described as about one cun from the midline, in the first posterior sacral foramen. One cun is roughly the width of your own thumb at the knuckle, or about 2 cm for most adults.

It sits awkwardly behind you, so it is easier to find lying on your side with your knees drawn up, or sitting and leaning forward. If you cannot clearly feel a dip, stay conservative and simply work the soft tissue over the upper sacrum rather than hunting for a precise hole.

How do you apply pressure to BL31?

1. Get into position. Lie on your side with your knees bent, or sit and lean forward over a table. Both positions let your hand reach behind you without straining your shoulder.
2. Locate the hollow. Place the pad of your thumb, or the flat of a bent middle knuckle, in the first sacral dip you found. Use the pad, not the nail.
3. Press straight in. Apply steady pressure toward the bone, gradually over two or three seconds. There is no rubbing needed at first.
4. Judge the strength. Aim for a firm, achy pressure that you would call about four or five out of ten. It should feel like pressing a bruise that is almost gone. Sharp, burning or electric sensations mean ease off immediately.
5. Hold and breathe. Keep the pressure for 20 to 60 seconds while breathing slowly. Then release over a couple of seconds rather than letting go suddenly.
6. Repeat on both sides. Do the same on the opposite side so your lower back is worked evenly. Two or three rounds per side is plenty.
7. Add gentle circles if you like. Small, slow circles for 30 seconds can suit a stiff, achy sacrum better than a static hold.
8. Keep sessions short. Two or three minutes per side, once or twice a day, is a sensible ceiling. More is not better here.

Stop straight away if you feel shooting pain down a leg, pins and needles, numbness, or any increase in pain that lasts after you let go. Stop too if the skin over the sacrum reddens and stays sore, which usually means you pressed too hard for too long.

This is finger pressure only. Never break the skin, and do not use needles, heat sticks, cups or any device that marks or burns the skin at BL31. If something feels like it needs more force than your thumb can give, that is a sign to see a clinician instead.

What is BL31 traditionally used for?

• Period pain. The baliao group is one of tradition's main choices for cramping period pain, known as dysmenorrhoea. Human trials of acupressure for period pain exist, but they usually use other points such as SP6, are small and unblinded, and rarely test BL31 alone. A warm hand on an aching sacrum may simply feel good, which is not nothing, but it is not proof.
• Low back and sacral ache. Classical use covers stiffness and heaviness across the lower back and sacrum. Evidence for massage and pressure on the low back in general is modest and short-lived. There is no good trial isolating BL31 for back pain.
• Urinary difficulty. Tradition links the baliao points to the bladder, and clinic research has used the lower points of the group, notably BL33, with needles and electrical stimulation for urinary leakage in women. That work is about needling in a clinic, not about pressing BL31 with a thumb, so it cannot be transferred to self-care.
• Irregular periods and pelvic complaints. Texts list BL31 for irregular cycles, vaginal discharge and infertility. There is no reliable human evidence that finger pressure changes any of these. Fertility and cycle problems need proper investigation.
• Constipation and bowel sluggishness. Traditional use includes bowel trouble. Evidence here is thin and mostly comes from abdominal points rather than sacral ones.
• Sciatic-type leg pain. Because the Bladder channel runs down the back of the leg, BL31 is sometimes used for pain spreading into the buttock and thigh. Pressure may ease muscle tension, but nerve pain that is new, worsening or linked to weakness needs assessment first.

Overall, the fair summary is that tradition uses BL31 confidently and the human evidence for self-applied pressure at this specific point is close to absent. Use it for comfort, and keep your expectations modest.

What might regular use of BL31 help prevent?

• Nothing has been shown to be prevented. No credible human study shows that regular finger pressure at BL31 prevents period pain, back pain, urinary problems or any other condition. Prevention claims you may see online are extensions of tradition, not findings.
• Traditional claim: smoother cycles. Some teaching suggests working the sacral points in the days before a period to reduce the cramping that follows. This has not been tested properly for BL31 as acupressure, so treat it as a comfort habit rather than prevention.
• Possible indirect benefit: tension habits. A short, regular routine that makes you sit down, breathe slowly and ease a tight lower back may help you notice strain earlier. That is a general effect of taking a break, not a specific effect of this point.
• What actually prevents these problems. For low back trouble, regular movement, strength work and sleep matter far more. For period pain, there are proven medical options worth discussing with a doctor. For urinary leakage, pelvic floor training taught by a physiotherapist has solid trial support.

A fair way to think about it is this. BL31 may make a bad day a little more bearable. There is no good reason to believe that pressing it today stops a problem tomorrow.

If you want to use it preventively anyway, keep it brief and gentle, and keep doing the things that are known to work. Never skip or delay a medicine, a check-up or a physiotherapy programme because you are relying on a pressure point. And if you are pregnant, or might be, this is not a point to add to any routine at all.

Are there tips for using BL31 effectively?

• Do not press BL31 if you are pregnant or think you might be. This is the single most important rule for this point. Every teaching tradition lists the sacral points as ones to avoid in pregnancy, and the sensible response is to leave BL31 alone entirely from the moment pregnancy is possible.
• Leave labour to professionals. Sacral points are sometimes used around childbirth in hospitals and birth centres. Whether, when and how that happens is a decision for your midwife or doctor, never something to try yourself or have a partner try at home.
• Warm the area first. A few minutes with a warm pack or a hot shower on the lower back makes the tissue easier to work and the pressure more comfortable.
• Use a knuckle for reach. Thumbs tire quickly at an awkward angle. The flat of a bent index finger knuckle gives steadier pressure without straining your wrist.
• Work both sides. BL31 is paired. Treating only the sore side tends to leave the lower back feeling lopsided.
• Lying on your side beats standing. Drawing your knees up opens the sacral area and relaxes the buttock muscles, so you can feel the hollow more clearly.
• Keep a simple note. Write down what you pressed and how you felt an hour later. Over a few weeks you will see whether it genuinely helps you or just feels nice at the time.
• Pair it with movement. Gentle walking or a few pelvic tilts after a session usually does more for a stiff back than pressure alone.
• Stop at the first sharp signal. Shooting pain, numbness or tingling down a leg means remove the pressure and do not go back to that spot.

What do people get wrong with BL31?

• Using it in pregnancy. Do not press BL31 if you are pregnant or think you might be. People see sacral points recommended for back ache in pregnancy videos and copy them. This is exactly the point tradition says to keep away from, and the safe answer is to skip it.
• Trying to start labour. Some articles suggest sacral pressure to bring on contractions. That is not a decision for you or your partner. A midwife or doctor decides anything to do with starting labour.
• Pressing the spine itself. The midline of the sacrum is bony ridge, not point. If your thumb is on a hard bump with no give, you are too close to the centre. Move about a thumb-width out.
• Confusing BL31 with its neighbours. Going too low lands on BL32 or BL33. Going too high and too far out lands on the pelvic rim near BL23 territory. BL31 is the uppermost hollow, roughly level with the dimple.
• Grinding until it bruises. Hard digging with a knuckle for minutes on end leaves the sacrum tender for days and helps nothing.
• Expecting a cure. BL31 does not cure period pain, back pain, bladder problems or infertility. Anyone promising that is selling something. Expect modest, short-lived comfort at best.
• Pressing over damaged skin or bone. A rash, boil, broken skin, a healing wound, a recent tailbone or pelvic injury, or fresh surgery in the area all mean hands off until it is healed and cleared.
• Ignoring red flags. Using pressure to manage numbness in the groin, leg weakness, or new loss of bladder or bowel control is dangerous. Those are emergency symptoms.
• Replacing real treatment. Pelvic floor physiotherapy and proper medical care for period pain have evidence behind them. Acupressure at BL31 does not replace either.

What does the research on BL31 actually say?

There is no good human research on BL31 used on its own as self-applied finger pressure. What exists studies the sacral group as a whole, usually with needles in a clinic, and usually not at BL31.

The strongest work in this area concerns urinary leakage in women. A large Chinese randomised trial published in a major general medical journal in 2017 compared electroacupuncture at lower sacral points, including BL33 and BL35, with a sham procedure for stress urinary incontinence (PMID 28655016). It reported a modest reduction in urine leakage over six weeks. Two points matter for this page. The trial needled and electrically stimulated the points, which is nothing like thumb pressure, and it did not target BL31.

For period pain, there are several small randomised acupressure trials, but they overwhelmingly use SP6 on the inner ankle or abdominal points. They tend to be short, unblinded and run in single centres, and they often rely on participants rating their own pain while knowing which group they were in. That design inflates apparent benefit. BL31 is rarely isolated in them.

Sacral pressure and massage during labour has been studied as part of general comfort care, and reviews of massage in labour suggest some reduction in reported pain. Those studies look at broad back massage, not at a single named point, and they take place with trained staff present.

So the fair summary is this. The sacral region has attracted serious clinical research, but almost all of it involves needling, trained practitioners and points below BL31. Treat claims that BL31 acupressure treats bladder disease, infertility or period problems as untested. If you find a video citing a study for BL31 specifically, check whether the study actually used that point and whether it used fingers or needles. Most of the time it did neither.