Index of Herbs

Concern guide

Herbs for Blood Sugar

Herbs that may support healthy blood sugar alongside medical care, from psyllium to cinnamon, with what the research shows.

9 herbs reviewed

Updated October 7, 2026

Blood sugar, or glucose, is the body’s main fuel, and insulin is the hormone that moves it into cells. In type 2 diabetes the body does not make enough insulin or use it well, and in prediabetes levels sit above normal but below the diabetes range. Both are very common, often cause no symptoms for years, and over time raised blood sugar can affect the heart, nerves, eyes, and kidneys. The encouraging news is that steady changes make a real difference: in the NIH’s Diabetes Prevention Program, regular activity and losing 5% to 7% of body weight lowered the chance of developing type 2 diabetes.

Herbs can be one part of a wider plan for healthy blood sugar, especially for people with prediabetes or type 2 diabetes who are working with a clinician. Psyllium fiber and fenugreek seed may help soften the rise in glucose after meals, and several other herbs have encouraging small trials. They work best alongside the foundations: balanced meals, regular activity, good sleep, a healthy weight, and any medicines your care team prescribes. No herb treats diabetes or replaces insulin, metformin, or other diabetes medicines, and NCCIH notes that no herbal supplement has yet been shown to reliably control diabetes. People with type 1 diabetes always need insulin, and herbs are never a substitute for it.

The herbs below are ordered by strength of evidence for blood sugar, then by how commonly they are used. Ratings run from good clinical evidence to long traditional use, and for blood sugar the best-supported herbs currently sit at promising. Research is still emerging: most trials are small and short, test different products and doses, and often measure fasting glucose rather than HbA1c, the average over the past few months that matters most in diabetes care, so larger trials would help. Because any herb that lowers glucose can add to diabetes medicines, each entry notes its key caution, and the full monographs cover doses, side effects, and interactions.

02 The shortlist

The herbs, from best studied to time-honored

How to read the ratings

  • Good clinical evidence
  • Promising clinical evidence
  • Early or mixed evidence
  • Long traditional use

Ratings show how much research backs each herb for this particular concern. Every herb links to its full monograph, with preparations, safety notes, and sources.

  1. 01 Psyllium

    Promising clinical evidence

    Plantago ovata

    Psyllium husk is a gentle soluble fiber that forms a gel in the gut and may soften the rise in blood sugar after meals. In a 2015 analysis of 35 trials, psyllium taken before meals lowered fasting glucose by 37 mg/dL and HbA1c by almost one percentage point in people treated for type 2 diabetes, with a smaller effect in prediabetes; most authors worked for a psyllium maker, so independent trials would help. Take it with plenty of water, half an hour to an hour apart from medicines, and tell your care team.

    Read the psyllium monograph →

  2. 02 Fenugreek

    Promising clinical evidence

    Trigonella foenum-graecum

    Fenugreek seed is a maple-scented kitchen spice with a long history in Indian and Middle Eastern medicine. Two meta-analyses found that seed powder lowered fasting glucose and HbA1c in type 2 diabetes and prediabetes, mainly at doses of several grams a day, and in a three-year study of adults with prediabetes fewer people taking it developed diabetes. Trials are still small and of mixed quality. Avoid it in pregnancy and with peanut or other legume allergy, and check with your prescriber if you take warfarin.

    Read the fenugreek monograph →

  3. 03 Cinnamon

    Early or mixed evidence

    Cinnamomum verum

    Cinnamon is the best-known blood sugar spice, and several meta-analyses find modest falls in fasting glucose. Results vary, though: a Cochrane review found too little evidence to recommend it, and pooled trials generally show no clear change in HbA1c, so it is best enjoyed in meals rather than relied on. Most trials used cassia cinnamon, which is rich in coumarin, a compound that can harm the liver in sensitive people. Ceylon cinnamon contains only traces, making it the better choice for regular use.

    Read the cinnamon monograph →

  4. 04 Ginseng

    Early or mixed evidence

    Panax ginseng

    Asian and American ginseng are classic tonic roots, and both have been studied for blood sugar. A 2022 meta-analysis of 20 trials in prediabetes and type 2 diabetes found lower fasting glucose and improved insulin resistance, though species, products, and doses varied widely, so trials of clearly defined products would help. Ginseng can add to the glucose-lowering effect of insulin and other diabetes drugs, American ginseng reduced the effect of warfarin in a trial, and it is best stopped a week before surgery.

    Read the ginseng monograph →

  5. 05 Milk Thistle

    Early or mixed evidence

    Silybum marianum

    Milk thistle is best known as a liver herb, but small trials, mostly from the Middle East, suggest its extract silymarin may help blood sugar in type 2 diabetes. A 2016 review of five trials with 270 people found fasting glucose about 27 mg/dL lower and HbA1c about 1.1 percentage points lower, an encouraging result that still needs confirming in larger, well-run trials elsewhere. It is generally well tolerated, but avoid it with ragweed or daisy-family allergy and in pregnancy.

    Read the milk thistle monograph →

  6. 06 Black Seed

    Early or mixed evidence

    Nigella sativa

    Black seed (Nigella sativa) is a treasured remedy in Islamic and South Asian tradition, with a growing set of diabetes trials. A meta-analysis of seven trials in type 2 diabetes found fasting glucose about 18 mg/dL lower and HbA1c 0.71 percentage points lower, and in one trial added to diabetes tablets, 2 g of seed a day worked best. The studies were small and short, so larger trials would help. It can add to diabetes and blood pressure drugs, and rare kidney injury has been reported.

    Read the black seed monograph →

  7. 07 Holy Basil

    Early or mixed evidence

    Ocimum tenuiflorum

    Holy basil, or tulsi, is a sacred Ayurvedic herb often enjoyed as a calming tea. In a small crossover trial in type 2 diabetes, fasting glucose fell by 21 mg/dL while people took holy basil leaves rather than placebo leaves, and in a 90-day study adding it to glibenclamide gave slightly better glucose and HbA1c than the drug alone. Most studies are small and short. Avoid it when pregnant or trying to conceive, and check with your doctor if you have thyroid disease or take anticoagulants.

    Read the holy basil monograph →

  8. 08 Stinging Nettle

    Early or mixed evidence

    Urtica dioica

    Nettle leaf is a nourishing traditional herb that has been tested in several small diabetes trials. A 2020 meta-analysis of eight trials with 401 people with type 2 diabetes found fasting glucose about 18 mg/dL lower with nettle, though HbA1c and insulin resistance did not change significantly and results varied widely between studies. It is generally gentle, with mild stomach upset the usual complaint, but an older man developed low blood sugar on a nettle-containing remedy, so check your glucose more closely when starting it.

    Read the stinging nettle monograph →

  9. 09 Astragalus

    Early or mixed evidence

    Astragalus mongholicus

    Astragalus is a Chinese tonic root with a long history of use. NCCIH reports a 2024 review of 20 studies in 953 adults with type 2 diabetes in which astragalus added to metformin lowered fasting glucose and HbA1c more than metformin alone. That is a hopeful finding, but most studies were of low quality, so better-designed trials are needed. Astragalus may lower blood sugar further with diabetes medicines and may raise lithium levels, and it is best avoided with autoimmune disease, transplant drugs, pregnancy, and breastfeeding.

    Read the astragalus monograph →

03 Caution

Using these herbs safely

Most of these herbs are well tolerated in the doses used in trials, and a few sensible precautions help keep it that way. The most important is never to stop, reduce, or swap insulin, metformin, or any other diabetes medicine without your prescriber, even if your readings improve; people with type 1 diabetes always need insulin. Some situations need prompt medical care rather than a herb. Very high readings with intense thirst and frequent urination, unexplained weight loss, nausea or vomiting, deep or fast breathing, fruity-smelling breath, drowsiness, or confusion can signal diabetic ketoacidosis (DKA) or another dangerous high-sugar state, which is an emergency: call 911 or go to the emergency room. New thirst, frequent urination, blurred vision, or slow-healing sores in someone without a diagnosis deserve a blood sugar test.

Because these herbs may lower glucose, combining them with diabetes medicines can sometimes push it too low, especially with insulin or sulfonylureas such as glipizide or glibenclamide (glyburide). Signs of low blood sugar include shakiness, sweating, hunger, a fast heartbeat, irritability, and confusion; follow the plan your care team gave you, and get urgent help if symptoms do not improve after a sugary snack or the person becomes less alert. When starting, stopping, or switching a herb, check your glucose more often, tell your care team, and add only one new product at a time. Several herbs also affect other medicines: fenugreek and black seed may strengthen the effect of warfarin, holy basil may slow clotting, and American ginseng reduced warfarin’s effect in a trial, so anyone on an anticoagulant needs closer INR checks. Psyllium can slow the absorption of other medicines, so take it at least half an hour to an hour apart from them. Berberine supplements are widely sold for blood sugar, and goldenseal, which contains berberine, is sometimes taken the same way; goldenseal inhibits the CYP3A4 and CYP2D6 enzymes that clear many prescription drugs, and berberine can interact with medicines too, so check with a pharmacist first.

A few herbs have specific cautions worth knowing. Cassia cinnamon, the most common type in North America, contains coumarin, which has caused liver injury in sensitive people; Germany’s Federal Institute for Risk Assessment calculates that a 60 kg adult reaches the tolerable daily intake with about 2 g of cassia a day, so people with liver disease should avoid cassia supplements and regular users may prefer Ceylon cinnamon. Psyllium must be taken with plenty of liquid, at least 30 ml per gram, because too little can cause choking or bowel blockage, and it is unsuitable with swallowing problems or a narrowed bowel. Fenugreek is a legume that can cross-react with peanut allergy, milk thistle can trigger reactions in people allergic to ragweed or daisies, holy basil may lower thyroid hormone, and astragalus is best avoided with autoimmune disease or transplant drugs. Kidney disease is common with diabetes, and NCCIH notes that some supplements have been linked to kidney damage, so people with kidney problems need closer monitoring; black seed has rare reports of acute kidney injury. Butcher’s broom, sold for leg veins, has been linked to a case of diabetic ketoacidosis and is best avoided with diabetes.

Pregnancy and breastfeeding: high blood sugar in pregnancy, including gestational diabetes, needs care from an obstetric team. Fenugreek in more than food amounts is not considered safe in pregnancy because it has been linked to birth defects, and EMA also advises against it while breastfeeding; holy basil should be avoided when pregnant or trying to conceive; EMA does not recommend medicinal cinnamon, milk thistle, or nettle herb in pregnancy or breastfeeding; and ginseng, black seed, and astragalus supplements are best avoided. EMA considers psyllium husk acceptable in pregnancy and breastfeeding when needed. Children with signs of high blood sugar need a pediatric assessment, because type 1 diabetes often begins in childhood and can progress quickly. Product quality varies: cinnamon labels often do not say whether they contain cassia or Ceylon, ginseng products may contain different species, and multi-ingredient blood sugar blends make it hard to know what helped or caused a side effect. Look for products that name the plant, the part used, and the dose, ideally with independent quality testing.

04 Questions

Frequently Asked Questions

The best-supported options are psyllium, a soluble fiber that lowered fasting glucose and HbA1c in people treated for type 2 diabetes when taken before meals, and fenugreek seed, which lowered both measures in two meta-analyses of small trials. Cinnamon is the most popular, though its results vary between studies. No herb replaces diabetes medicine, and the biggest gains still come from food choices, activity, a healthy weight, and the treatment your care team recommends.

Sometimes, but only with your care team’s knowledge, and never as a reason to change your dose yourself. Herbs that lower glucose, such as fenugreek, holy basil, and black seed, can add to the effect of diabetes medicines and may cause low blood sugar, with shakiness, sweating, or confusion; the risk is highest with insulin and sulfonylureas. Check your glucose more often when you start or stop a herb, and take psyllium at least half an hour to an hour apart from your tablets.

Cinnamon in food is fine for most people, and some meta-analyses find modest falls in fasting glucose, though not a clear change in HbA1c. The concern with daily supplements is coumarin in cassia, the most common cinnamon in North America, which has caused liver injury in sensitive people. Germany’s risk assessment agency calculates that a 60 kg adult reaches the tolerable daily limit with about 2 g of cassia, so Ceylon cinnamon is the better choice for regular use, and people with liver disease should avoid cassia supplements.

Berberine, a compound found in goldenseal, barberry, and Oregon grape, has encouraging research of its own: NCCIH describes a 2021 review of 46 studies suggesting it may lower blood glucose in type 2 diabetes, especially alongside standard treatment, though many studies were of poor quality. Whole goldenseal root has not been tested for blood sugar and is not the same product. Goldenseal inhibits liver enzymes that clear many prescription drugs, and berberine can interact with medicines too, so check with a pharmacist; neither should be used in pregnancy, while breastfeeding, or in infants.

Most trials ran for several weeks to a few months before measuring results. Psyllium was taken before meals for several weeks, black seed and holy basil trials lasted about three months, and the prediabetes study of fenugreek ran for three years. HbA1c reflects your average blood sugar over the past few months, so it is best to judge any change with your care team at your next scheduled test, while checking your daily readings more closely in the meantime.

05 References

Sources

These references support the claims in this guide. Each herb’s monograph carries its own full source list.

  1. Diabetes and Dietary Supplements: What You Need To Know

    National Center for Complementary and Integrative Health (NIH), 2023

    Supports the statements that no herbal supplement has been shown to reliably control diabetes, that medical treatment should never be replaced, and the berberine, cassia coumarin, and kidney cautions.

  2. Symptoms & Causes of Diabetes

    National Institute of Diabetes and Digestive and Kidney Diseases (NIH), 2024

    Source for diabetes symptoms, unexplained weight loss in type 1 diabetes, DKA as an emergency, and the Diabetes Prevention Program finding on activity and 5% to 7% weight loss.

  3. Diabetic ketoacidosis

    MedlinePlus Medical Encyclopedia, National Library of Medicine (NIH), 2025

    Lists DKA symptoms, including thirst, frequent urination, fruity breath, and decreased alertness, and advises emergency care.

  4. Low blood sugar

    MedlinePlus Medical Encyclopedia, National Library of Medicine (NIH), 2026

    Source for the signs of hypoglycemia, such as shaking, sweating, and unclear thinking, its link with insulin and some diabetes medicines, and when to seek emergency help.

  5. Psyllium fiber improves glycemic control proportional to loss of glycemic control: a meta-analysis of data in euglycemic subjects, patients at risk of type 2 diabetes mellitus, and patients being treated for type 2 diabetes mellitus

    American Journal of Clinical Nutrition (PubMed 26561625), 2015

    The 35-trial analysis behind the psyllium rating, showing lower fasting glucose and HbA1c in treated type 2 diabetes; largely written by manufacturer employees.

  6. The Effect of Fenugreek in Type 2 Diabetes and Prediabetes: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

    International Journal of Molecular Sciences (PubMed 37762302), 2023

    Ten trials with 706 participants showing lower fasting glucose, two-hour glucose, and HbA1c with fenugreek, supporting its some rating.

  7. Cinnamon for diabetes mellitus

    Cochrane Database of Systematic Reviews (PubMed 22972104), 2012

    Ten trials with 577 participants finding no significant effect on HbA1c and insufficient evidence to support cinnamon for diabetes, the basis for its mixed rating.

  8. FAQ on coumarin in cinnamon and other foods

    German Federal Institute for Risk Assessment (BfR), 2012

    Source for the coumarin liver caution and the calculation that a 60 kg adult reaches the tolerable daily intake with about 2 g of cassia a day.

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