What do dark veins under the tongue mean: Brehan Crawford, L.Ac., showing how to lift the tongue to check the sublingual veins

What Do Dark Veins Under the Tongue Mean?

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    The reason behind your constant headaches could be hiding under your tongue. The underside of the tongue is the only place on your body where the tissue is thin enough to actually see the blood traveling underneath. If the two veins there look dark purple or blue, Chinese medicine calls it blood stasis: your blood is not moving freely through your arteries and veins.

    The short answer

    Dark purple or blue veins under the tongue are the classic sign of blood stasis in Chinese medicine. Stasis can cause recurring headaches, painful periods, chronically cold hands and feet, or even worse problems. These are not separate complaints. They share one underlying pattern, and that pattern is what we treat, often without harsh medications, sometimes with something as simple as herbal patches placed in the right spots.

    The short version, on video.

    What do dark veins under the tongue mean in Chinese medicine?

    In Chinese medicine, dark purple or blue veins under the tongue mean blood stasis. Blood is supposed to flow. When it slows, pools and thickens, the veins that drain the tongue fill out and darken, and because the lining under the tongue is so thin, you can see it happen.

    Practitioners have read the sublingual veins for centuries, and the sign holds up when it is measured with modern tools. A team at the Department of Kampo Medicine at Chiba University Hospital in Japan photographed the tongues of 38 patients with a tongue image analyzing system and split them by vein width: 20 patients with sublingual veins 2.5 mm wide or less, and 18 with veins wider than 2.5 mm.[1] Wider veins went with measurably darker and bluer color at the edge, tip and back of the tongue. Reading the tongue color and the vein together diagnosed blood stasis more accurately than either one alone. In Japanese Kampo the pattern is called oketsu; in Chinese it is yu xue. Both mean the same thing: blood that has stopped moving the way it should.

    Clinicians in Taiwan went further and trained a computer to grade sublingual veins as mild or severe. The sublingual vein is examined in Chinese medicine to determine the presence of blood stasis, and, as that team notes, many studies have shown that the degree of stasis in these veins rises with the severity of disease. Their best model sorted the images with 87.5% accuracy, about the same as experienced Chinese medicine physicians.[2]

    This is a different reading from the coating and shape of the tongue, which is covered in What Your Tongue Is Telling You. The top of the tongue tells you about digestion and heat. The underside tells you about circulation. If you want to learn to read both on yourself, that is the kind of thing we teach step by step in Gut Brain Synchrony.

    What does dirty blood mean?

    When people say "dirty blood," what Chinese medicine actually describes is stagnant blood: blood that has slowed down, grown thick and sticky, and stopped reaching the places it needs to reach. The problem is not that the blood is full of dirt. The problem is that it is not moving.

    Modern lab work gives that idea a concrete shape. A meta-analysis of 30 trials covering 10,323 patients with coronary heart disease compared those diagnosed with blood stasis syndrome against those without it. The blood stasis group had higher platelet aggregation and higher fibrinogen, and the review concluded that blood stasis went with increased platelet function, hypercoagulability and decreased fibrinolytic activity.[3] In plain terms, blood that clots more readily and clears its clots more slowly. That is about as close as science comes to "dirty blood," and it is exactly what the old diagnosis was pointing at.

    What does dark purple veins under the tongue mean for the rest of the body?

    Dark, swollen veins under the tongue reflect what the blood is doing everywhere else. That is why blood stasis can cause not only recurring headaches, but also painful periods, chronically cold hands and feet, or even worse problems.

    Dentists in Sweden have spent fifteen years documenting the "even worse problems" part. In 431 dental patients, Hedström and colleagues found that people with medium or severe sublingual varices were more likely to have hypertension (odds ratio 2.25), with a mean systolic pressure of 132 mmHg against 123 mmHg in those without them. The varices indicated hypertension with a positive predictive value of 0.5 and a negative predictive value of 0.80, and the authors wrote that examining the tongue is easily done and causes no harm.[4]

    The same group then photographed the tongues of 989 dental patients aged 55 to 84. Those with sublingual varices had more hypertension (41.8% vs 27.0%), more type 2 diabetes (7.4% vs 3.8%) and more dyslipidemia (24.1% vs 17.7%).[5] When they followed 1,139 patients forward in time, new heart disease events occurred in 4.5% of those with varices compared with 1.8% of those without, and new cerebrovascular events in 4.2% compared with 2.0%. The veins were seen before the heart events happened.[6]

    Pooled reviews agree. A meta-analysis of twelve studies found a significant association between sublingual varices and hypertension (odds ratio 2.66).[7] Another, of eleven studies and 2,272 patients, linked them to hypertension, diabetes, smoking and varicose veins in the legs.[8] That last finding matters. The veins under the tongue and the veins in the legs are showing the same thing.

    Why are headaches, painful periods and cold hands the same pattern?

    These three are not even separate from each other. They all have the same underlying pattern, and that pattern is what we treat. Western medicine sends you to a neurologist for the headaches, a gynecologist for the cramps, and nobody at all for the cold feet. Chinese medicine looks at the terrain underneath all three.

    Headaches from blood stasis

    Blood stasis headache is its own recognized category in Chinese medicine. Stasis headaches are classically fixed in one place, stabbing or boring, and they keep coming back. A 2024 review of 112 papers on treating blood stasis headache with acupuncture and moxibustion analyzed 102 complete point prescriptions.[9] Removing stasis is also one of the three core treatment strategies Chinese medicine uses for migraine, with herbs such as Chuan Xiong chosen to promote blood circulation and improve the flow properties of the blood.[10] For the early-warning side of migraine, see How to Stop a Migraine Before It Starts.

    Painful periods from blood stasis

    The uterus has to move a lot of blood every month. When that blood is stagnant, it does not leave smoothly; it cramps, clots and hurts. Qi stagnation and blood stasis is one of the standard diagnoses for primary dysmenorrhea, and researchers at Kyung Hee University used it to recruit 24 women with significant period pain, comparing them with 24 women with little pain across a full menstrual cycle. A computerized tongue analysis showed measurable differences between the two groups during menstruation.[11] The tongue tracks the cycle.

    Cold hands and feet from blood stasis

    Warmth travels with blood. If blood is not reaching the far ends of the body, the hands and feet are the first to go cold. A systematic review of 14 randomized trials (974 participants) on cold hypersensitivity in the hands and feet notes that the problem is especially common in women and may be associated with gynecological problems: the same link between cold extremities and the menstrual cycle that Chinese medicine has drawn for centuries. Herbal medicine reduced the symptoms (risk ratio 0.31), and in the one placebo-controlled study it raised skin temperature and peripheral blood flow.[12] In a double-blind trial of 80 women with cold hands and feet, Korean red ginseng, used in Korean medicine to improve blood flow, produced higher skin temperature in the hands and feet than placebo after eight weeks.[13]

    Three complaints, one cause: blood that is not moving. Treat the movement and you are treating all three at once.

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    Headaches, cramps and cold feet, treated as one pattern

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    How do herbal patches help blood stasis?

    If the veins under your tongue are dark purple, you can often find relief without using harsh medications that come with nasty side effects. A review of Chinese medicine for migraine opens on exactly that point: commercially available Western migraine drugs are prone to side effects, and Chinese medicine works by treating both the symptoms and the root cause.[10]

    It can be as simple as herbal patches. They are wonderful for many kinds of chronic pain, including headaches. A patch holds blood-moving herbs against the skin for hours, working on the area underneath and on the acupuncture point it covers. The evidence for the format is substantial. A systematic review of one herbal pain plaster pooled 22 randomized trials with 2,556 participants, comparing it against anti-inflammatory drugs, glucosamine, steroid injections, hyaluronic acid and acetaminophen; ten of those trials found the plaster more effective at improving pain, stiffness and function.[14]

    Where you put the patch matters

    A patch works right when it goes in the right place. For blood stasis headache, the points acupuncturists reach for most often are Fengchi (GB20) at the base of the skull, Taiyang at the temple, Baihui (GV20) at the crown, Hegu (LI4) on the hand, Shuaigu (GB8) above the ear, Taichong (LR3) on the foot, and Xuehai (SP10), the "Sea of Blood," above the knee. Nearly half of all points used were on the head and neck.[9] For period pain, a placebo-controlled trial design from Chengdu places a plaster made from Shao Fu Zhu Yu Tang, the classical formula whose name means "drive out stasis from the lower abdomen," on Shenque (CV8) at the navel, Guanyuan (CV4) and Qihai below it, Ciliao (BL32) on the sacrum, and Zigong on the lower belly.[15] Same tool, different map. Knowing the map is the whole skill.

    How to check the veins under your tongue

    01 Find good light and a mirror. Daylight from a window is best. Avoid colored bulbs, which change how purple anything looks.
    02 Lift up your tongue. Touch the tip to the roof of your mouth without straining. You will see two veins running back on either side of the center fold.
    03 Read the color and the fullness. Faint, thin, pale blue lines are what moving blood looks like. Dark purple or deep blue veins, especially thick, swollen or branching ones, are blood stasis. The Chiba researchers used 2.5 mm as the line between a normal and an enlarged vein.[1]
    04 Put it next to your symptoms. Recurring headaches, painful periods, chronically cold hands and feet. If the veins are dark and one or more of these is familiar, you are looking at the same pattern from two sides.
    05 Get the blood moving, in the right places. Herbal patches are a simple place to start. Learn where they go for your pattern, on the head and neck for headache, on the lower abdomen and sacrum for period pain, so that they work right.

    Frequently asked questions

    Is it normal to have dark veins under your tongue?

    Everyone has veins under the tongue. Dark purple, blue or swollen ones are common, but common is not the same as healthy. In one Swedish study a third of dental patients had them, and those patients went on to have more new heart events than the rest.[6] In Chinese medicine, dark veins mean blood stasis.

    What causes blood stasis?

    Classically, anything that slows the blood: cold, which contracts the vessels; stagnant qi from long-term stress, since qi leads the blood; deficiency, when there is not enough qi to push the blood along; heat that thickens it; and old injuries that never fully resolved. Long illness of any kind tends to end in stasis.

    What does black veins under the tongue mean?

    Veins that look almost black are the same sign taken further: deep blood stasis. The darker and fuller the veins, the more the blood has slowed, which is why the Taiwanese team graded severity rather than just presence.[2]

    Lift your tongue tonight. It is the one place your body lets you watch your own blood move.

    — Brehan Crawford, L.Ac.

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    References

    1. Morita A, Murakami A, Noguchi K, et al. Combination Image Analysis of Tongue Color and Sublingual Vein Improves the Diagnostic Accuracy of Oketsu (Blood Stasis) in Kampo Medicine. Front Med (Lausanne). 2022;8:790542. doi:10.3389/fmed.2021.790542
    2. Lu PH, Chiang CC, Yu WH, Yu MC, Hwang FN. Machine Learning-Based Technique for the Severity Classification of Sublingual Varices according to Traditional Chinese Medicine. Comput Math Methods Med. 2022;2022:3545712. doi:10.1155/2022/3545712
    3. Xin QQ, Chen X, Yuan R, et al. Correlation of Platelet and Coagulation Function with Blood Stasis Syndrome in Coronary Heart Disease: A Systematic Review and Meta-Analysis. Chin J Integr Med. 2021;27(11):858-866. doi:10.1007/s11655-021-2871-2
    4. Hedström L, Albrektsson M, Bergh H. Is there a connection between sublingual varices and hypertension? BMC Oral Health. 2015;15:78. doi:10.1186/s12903-015-0054-2
    5. Bergh H, Albrektson M, Kastberg C, Baigi A, Hedström L. The Association Between Sublingual Varices and Cardiovascular Risk Factors. Vasc Health Risk Manag. 2022;18:319-327. doi:10.2147/VHRM.S354021
    6. Bergh H, Albrektson M, Kastberg C, Hedström L. Association of Sublingual Varices With Heart- and Cerebrovascular Disease. Int Dent J. 2024;74(2):216-222. doi:10.1016/j.identj.2023.08.003
    7. Eslami H, Halimi Milani F, Salehnia F, Kourehpaz N, Katebi K. Relationship between sublingual varices and hypertension: a systematic review and meta-analysis. BMC Oral Health. 2024;24(1):240. doi:10.1186/s12903-024-03982-8
    8. Costa AKLS, de Andrade ACM, Felix FA, et al. Sublingual varices as predictor of factors associated with cardiovascular diseases: A systematic review with meta-analysis. Oral Maxillofac Surg. 2024;29(1):15. doi:10.1007/s10006-024-01311-5
    9. Shi JY, Li TT, Yang HT, et al. Acupoints for Headache with Blood Stasis Syndrome: a Literature Study Based on Data Mining Technology. J Pain Res. 2024;17:2455-2471. doi:10.2147/JPR.S471441
    10. Huang Y, Ni N, Hong Y, Lin X, Feng Y, Shen L. Progress in Traditional Chinese Medicine for the Treatment of Migraine. Am J Chin Med. 2020;48(8):1731-1748. doi:10.1142/S0192415X2050086X
    11. Kim J, Lee H, Kim H, Kim JY, Kim KH. Differences in the Tongue Features of Primary Dysmenorrhea Patients and Controls over a Normal Menstrual Cycle. Evid Based Complement Alternat Med. 2017;2017:6435702. doi:10.1155/2017/6435702
    12. Yu JS, Lee D, Hyun D, Chang SJ. Herbal Medicines for Cold Hypersensitivity in the Hands and Feet: A Systematic Review and Meta-Analysis. J Altern Complement Med. 2018;24(12):1150-1158. doi:10.1089/acm.2018.0009
    13. Park KS, Park KI, Kim JW, et al. Efficacy and safety of Korean red ginseng for cold hypersensitivity in the hands and feet: a randomized, double-blind, placebo-controlled trial. J Ethnopharmacol. 2014;158 Pt A:25-32. doi:10.1016/j.jep.2014.09.028
    14. Chen C, Li SQ, Bao T, Zhang L, Seluzicki C, Mao JJ. A Systematic Review of CheeZheng Pain Relieving Plaster for Musculoskeletal Pain: Implications for Oncology Research and Practice. Integr Cancer Ther. 2020;19:1534735420918933. doi:10.1177/1534735420918933
    15. Yu S, Wen Y, Xia W, et al. Acupoint herbal plaster for patients with primary dysmenorrhea: study protocol for a randomized controlled trial. Trials. 2018;19(1):348. doi:10.1186/s13063-018-2682-8