Cinnamon and Blood Glucose: Evidence and Safety

Cinnamon and blood glucose have become a popular topic in natural health circles, with many people wondering whether this common spice can genuinely help manage diabetes or prediabetes. Cinnamon contains bioactive compounds, including cinnamaldehyde and polyphenols, that show promise in laboratory studies for influencing insulin signalling. However, clinical evidence in humans remains inconsistent, and neither NHS nor NICE guidelines recommend cinnamon as a treatment for blood glucose management. This article examines what the research actually shows, how much cinnamon would be needed, safety considerations, and what evidence-based options are available in the UK.

Can cinnamon really help lower your blood sugar levels?

Cinnamon may produce a modest, short-term reduction in fasting blood glucose in some people with type 2 diabetes, but Diabetes UK states the evidence is insufficient to support its use as a treatment.

Cinnamon may have a modest, short-term effect on fasting blood glucose in some people with type 2 diabetes, but the evidence is inconsistent and it is not a substitute for prescribed treatment. Cinnamon is a spice derived from the bark of Cinnamomum trees, most commonly Cinnamomum cassia (cassia cinnamon) or Cinnamomum verum (Ceylon cinnamon). Both contain bioactive compounds, particularly cinnamaldehyde and various polyphenols, that laboratory and animal studies suggest may influence insulin signalling pathways.

In cell and animal models, these compounds appear to mimic insulin activity, enhance glucose uptake into cells, and slow the rate at which the stomach empties, which can blunt post-meal glucose spikes. These are preclinical findings, and what happens in a test tube or in a rodent does not always translate reliably to human physiology. This gap is important when evaluating cinnamon's real-world usefulness.

For people living with type 2 diabetes or prediabetes (also called non-diabetic hyperglycaemia), the appeal of a natural, widely available remedy is understandable. However, healthcare professionals caution that relying on cinnamon in place of evidence-based interventions, such as dietary change, physical activity, or prescribed medication, carries genuine risk. Blood glucose that is poorly controlled over time increases the risk of serious complications including cardiovascular disease, kidney damage, and neuropathy. Diabetes UK notes that the evidence for cinnamon as a glucose-lowering intervention is insufficient to support its use as a treatment. Cinnamon should therefore be considered, at most, a complementary interest rather than a therapeutic strategy, and any changes to diabetes management should be discussed with a GP or diabetes specialist.

What does the clinical evidence say about cinnamon and glucose control?

Clinical trials and meta-analyses show small, inconsistent reductions in fasting glucose and HbA1c with cinnamon supplementation, but study quality is variable and neither NICE nor Diabetes UK recommends it clinically.

Clinical trials examining cinnamon and blood glucose have produced mixed results, with some studies showing small reductions in fasting glucose and HbA1c, while others show no meaningful benefit. A meta-analysis published in the Journal of the Academy of Nutrition and Dietetics (2016) pooled data from randomised controlled trials and found statistically significant reductions in fasting plasma glucose associated with cinnamon supplementation, but the authors noted that the clinical significance of these reductions was uncertain and that study quality was variable. More recent systematic reviews and meta-analyses published between 2019 and 2024 have similarly concluded that any effects are modest, inconsistent across populations, and insufficient to support a clinical recommendation.

A Cochrane review on cinnamon for diabetes mellitus has not reached a definitive positive conclusion, and both Diabetes UK and NICE have noted that the evidence base does not support recommending cinnamon as a glucose-lowering intervention.^[6]

Key limitations across the evidence base include:

• Small sample sizes, often fewer than 100 participants per trial

• Short study durations, typically six to twelve weeks, which do not reflect long-term glycaemic management

• Heterogeneous populations, mixing people with type 2 diabetes, prediabetes (non-diabetic hyperglycaemia), and metabolic syndrome

• Varying cinnamon types and doses, making direct comparisons difficult

• Lack of blinding in some trials, which introduces placebo effects

It is also worth noting that most trials use concentrated cinnamon extracts rather than culinary quantities of the spice, meaning that adding cinnamon to porridge or coffee is unlikely to replicate even the modest effects seen in supplementation studies. The distinction between food-level and supplement-level intake is clinically relevant and often overlooked in popular health reporting.

How much cinnamon would you need to take to see any effect?

Trials reporting any glucose-lowering signal used 1 to 6 grams of cinnamon daily; cassia cinnamon at these doses can exceed EFSA's safe coumarin limit of 0.1 mg per kilogram of body weight per day.

Trials that have reported any glucose-lowering signal have generally used doses ranging from 1 gram to 6 grams of cinnamon powder daily, which is considerably more than the amounts typically used in cooking.^[3][4] One teaspoon of ground cinnamon weighs approximately 2 to 3 grams depending on grind and packing density, so even the lower end of the studied dose range represents a meaningful daily supplement rather than a culinary addition.

The type of cinnamon matters as much as the quantity. Cassia cinnamon, which is the most widely sold variety in UK supermarkets, contains significant levels of coumarin, a naturally occurring compound that can cause liver damage when consumed in large amounts over time. The European Food Safety Authority (EFSA) has established a tolerable daily intake (TDI) for coumarin of 0.1 mg per kilogram of body weight. For a person weighing 70 kg, this equates to approximately 7 mg of coumarin per day. Cassia cinnamon can contain between 1 mg and 12 mg of coumarin per gram of spice (figures cited by the German Federal Institute for Risk Assessment, BfR, and referenced by the UK Food Standards Agency), meaning that doses used in clinical trials could easily exceed safe coumarin limits if cassia is used.

Ceylon cinnamon contains far lower levels of coumarin and is generally considered safer for regular use, though it is less commonly available and more expensive. Anyone considering cinnamon supplementation should:

• Choose Ceylon cinnamon where possible to minimise coumarin exposure

• Frame any intake against the EFSA coumarin TDI of 0.1 mg per kilogram of body weight per day, rather than a fixed gram limit, because coumarin content varies by batch and origin

• Discuss supplementation with their GP before starting, particularly if they have liver disease or take regular medication

• Avoid high-dose cinnamon supplements during pregnancy or breastfeeding, as safety data in these groups are very limited; seek advice from a midwife or GP before use

Given these considerations, self-prescribing high-dose cinnamon supplements without professional guidance is not advisable.

Is it safe to use cinnamon alongside diabetes medication?

Cinnamon supplements can have additive glucose-lowering effects with insulin or sulfonylureas, risking hypoglycaemia, and coumarin in cassia cinnamon poses a hepatotoxicity risk at high doses.

Using cinnamon supplements alongside prescribed diabetes medication carries a risk of additive glucose-lowering effects that could lead to hypoglycaemia, particularly in people taking insulin or sulfonylureas such as gliclazide or glibenclamide.^[3] While the glucose-lowering effect of cinnamon is modest and inconsistent, combining even a small additional effect with a medication that already lowers blood glucose can occasionally push levels below the safe threshold, especially in older adults or those with variable dietary intake.

If you experience symptoms of hypoglycaemia (such as shakiness, sweating, confusion, or feeling faint), follow NHS guidance: consume a fast-acting carbohydrate such as glucose tablets or a small glass of fruit juice, then eat a starchy snack. If symptoms are severe or do not improve, call 999.

Cinnamon may also interact with other medicines. There is some in vitro evidence that cinnamon compounds can affect enzymes in the cytochrome P450 system, which is involved in the metabolism of many commonly prescribed medicines.^[12] Whether this translates to clinically meaningful interactions in humans is not established, and these concerns should be treated as theoretical unless confirmed by your prescriber or pharmacist.

Regarding anticoagulants: coumarin itself is not an anticoagulant, and the article does not claim otherwise. However, if you take warfarin or another anticoagulant and are considering regular high-dose cassia cinnamon supplements, discuss this with your GP or anticoagulant clinic, as any change in diet or supplementation warrants clinician-led INR monitoring.

People with pre-existing liver conditions should exercise particular caution, as coumarin hepatotoxicity, though rare, has been documented in case reports following prolonged high-dose cassia cinnamon consumption (BfR).^[11] Pregnant or breastfeeding individuals should avoid high-dose cinnamon supplements unless specifically advised by a clinician.

If you are taking any medication for diabetes or another long-term condition and are considering cinnamon supplements, speak with your GP or pharmacist before starting. Do not stop or reduce prescribed diabetes medication on the basis of perceived improvements in blood glucose from cinnamon, as this could be dangerous. Any suspected adverse effects from supplements can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

What do NHS and NICE guidelines say about herbal supplements for diabetes?

NICE guidelines (NG28) and NHS guidance do not recommend cinnamon or any herbal supplement for type 2 diabetes or prediabetes; evidence-based care focuses on diet, exercise, and prescribed medication.

Neither NHS guidance nor NICE guidelines recommend cinnamon or any other herbal supplement as a treatment for type 2 diabetes or prediabetes (non-diabetic hyperglycaemia). NICE guidelines on type 2 diabetes management (NG28 and its updates) focus on structured lifestyle interventions, evidence-based pharmacotherapy, and regular monitoring, with no mention of cinnamon or botanical supplements as adjuncts to care.^[7][8] These supplements are not routinely commissioned for NHS use by Integrated Care Boards, though commissioning decisions may vary locally.

The NHS advises people with diabetes to be cautious about health claims made for supplements and to rely on treatments that have been rigorously evaluated in clinical trials and authorised by the MHRA. The MHRA authorises medicines based on evidence of safety, quality, and efficacy, and no cinnamon product holds a full marketing authorisation as a glucose-lowering medicine in the UK.^[9][10] Some herbal products carry a Traditional Herbal Registration (THR), but this scheme confirms only that a product meets quality and safety standards for traditional use, not that it has been proven effective for any medical condition.^[9][10]

For people seeking support with blood glucose management, the most effective and evidence-based approaches remain:

• Structured dietary change, including reducing refined carbohydrates and following NHS-recommended healthy eating guidance for diabetes

• Regular physical activity, which improves insulin sensitivity

• Prescribed medication where indicated, such as metformin, GLP-1 receptor agonists, or SGLT2 inhibitors

• Regular HbA1c monitoring and review with a GP or diabetes nurse

• Structured education programmes such as DESMOND, which support self-management of type 2 diabetes

Bolt Pharmacy is a GPhC-registered UK online pharmacy offering online consultations with prescriber review and pharmacist support for people exploring clinically appropriate weight and metabolic health options. Anyone concerned about their blood glucose levels should contact their GP in the first instance, or call NHS 111 for urgent advice.

Scientific References

1. Cinnamon for Metabolic Diseases and Their Cardiovascular and Hepatic Complications: A Mechanistic Review.
2. Effects of 1 and 3 g cinnamon on gastric emptying, satiety, and postprandial blood glucose.
3. Do Cinnamon Supplements Have a Role in Glycemic Control in Type 2 Diabetes? A Narrative Review.
4. Effects of cinnamon supplementation on metabolic biomarkers in individuals with type 2 diabetes: a systematic review and meta-analysis.
5. The effect of cinnamon supplementation on glycemic control in patients with type 2 diabetes mellitus: An updated systematic review and dose-response meta-analysis of randomised controlled trials.
6. Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis.
7. Type 2 diabetes in adults: management (NG28).
8. Type 2 diabetes in adults: management – Initial medicines chapter (NG28).
9. Herbal medicines granted a traditional herbal registration (THR).
10. Apply for a traditional herbal registration (THR).
11. Do cinnamon supplements cause acute hepatitis?.
12. Pharmacokinetic Evaluation of a Cinnamon Product on CYP2A6 Substrate Drugs: Application of a Novel Tool Involving the Nicotine Metabolite Ratio.

Frequently Asked Questions