Does Cinnamon Break Intermittent Fasting?

Does cinnamon break intermittent fasting? It is a common question for anyone trying to keep their fasting window intact while enjoying a spiced drink. The short answer is that a small pinch of plain ground cinnamon in black coffee or water is unlikely to break a fast in any meaningful metabolic sense, as it contains negligible calories and virtually no digestible carbohydrate. However, the form cinnamon takes matters considerably, and certain health conditions or medications can make the combination of cinnamon supplements and fasting a more complex issue worth discussing with a clinician.

Does cinnamon break a fast, and does the form it's in matter?

Plain ground cinnamon in small amounts is unlikely to break a fast, as it contains negligible calories and minimal digestible carbohydrate. Cinnamon-flavoured products with added sugars, milk solids or sweeteners will end the fasting period.

Plain ground cinnamon used in very small amounts, such as a pinch stirred into black coffee or water, is unlikely to break a fast in any meaningful metabolic sense. Intermittent fasting works primarily by keeping insulin levels low and allowing the body to shift towards fat oxidation during the fasting window.^[3][4] Because pure cinnamon contains negligible calories and virtually no digestible carbohydrate in the quantities typically used (under half a teaspoon), it is unlikely to trigger a significant insulin response or interrupt ketosis.

The form cinnamon takes, however, does matter considerably. There is an important distinction between:

• Pure ground cinnamon (Ceylon or Cassia): minimal calories, no added sugars, generally considered fasting-compatible in small amounts

• Cinnamon supplements or capsules: usually calorie-free, but may contain fillers or binders worth checking

• Cinnamon-flavoured products: teas, syrups, protein powders or blended drinks that often contain added sugars, milk solids or sweeteners that can break a fast

• Cinnamon toast, baked goods or cereals: clearly calorie-containing and will end the fasting period

It is also worth noting that some researchers debate whether any caloric intake, however small, technically ends a fast at a cellular level. For most people following intermittent fasting for general health or weight management, a pinch of cinnamon in a hot drink is unlikely to undermine their goals. Those following a stricter protocol, such as extended fasting or fasting for specific metabolic investigations, may prefer to avoid it entirely during the fasting window. Anyone fasting for a medical test or procedure should follow their clinician's specific instructions, which may differ from general guidance.

Which cinnamon products are safe to use while fasting?

Pure ground cinnamon and plain cinnamon herbal teas with no added ingredients are the safest choices during a fasting window. Avoid cinnamon syrups, spiced lattes or any product listing sugars or dairy alongside cinnamon.

Pure ground cinnamon and plain cinnamon herbal teas with no added ingredients are the safest choices during a fasting window. When selecting a product, reading the ingredient list carefully is essential, as many commercially available cinnamon products contain hidden sugars, honey or maltodextrin that add calories and may affect blood glucose.

Regarding artificial sweeteners: current NHS and Diabetes UK guidance indicates that non-nutritive sweeteners do not meaningfully raise blood glucose or insulin levels in most people, so the primary concern with sweetener-containing products during a fast is whether they contribute calories rather than a direct insulin effect.^[5][6]

The following guidance can help when choosing cinnamon products during a fast:

• Ceylon cinnamon (sometimes labelled "true cinnamon") is lower in coumarin, a naturally occurring compound found in higher concentrations in the more widely available Cassia variety. The Food Standards Agency (FSA) advises that people who use cinnamon regularly or in larger amounts may wish to choose Ceylon cinnamon to limit coumarin exposure. This distinction becomes particularly relevant with regular or high-dose use.

• Cinnamon sticks steeped in hot water produce a lightly flavoured drink with negligible caloric content and are generally considered fasting-compatible.

• Cinnamon capsules or supplements: check the label for excipients such as maltodextrin, starch or sugar coatings, which could add a small caloric load.

• Herbal tea blends: many cinnamon teas contain additional ingredients such as liquorice root, apple pieces or honey that may add sugars or have pharmacological effects of their own. Check the full ingredient list before use.

• Avoid: cinnamon-flavoured coffee syrups, spiced lattes, cinnamon rolls, granola or any product where cinnamon is listed alongside sugars or dairy.

For those who are uncertain about a specific product, contacting the manufacturer directly or consulting a pharmacist can help clarify the ingredient profile. A GPhC-registered online pharmacy such as Bolt Pharmacy offers pharmacist support and weight-management consultations where questions about fasting protocols and supplement use can be discussed with a qualified clinician. Ultimately, the simpler the product, the easier it is to be confident it will not interfere with the fasting state.

Is intermittent fasting safe if you take cinnamon supplements?

For most healthy adults, cinnamon supplements during intermittent fasting pose little risk, but Cassia extracts carry coumarin exposure concerns and may lower blood glucose, increasing hypoglycaemia risk in people on diabetes medication.

For most healthy adults, taking a cinnamon supplement during an intermittent fasting protocol is unlikely to pose a significant safety concern, provided the supplement is taken as directed and the individual has no relevant underlying health conditions. However, there are important considerations that should not be overlooked.

Cinnamon supplements, particularly those containing Cassia cinnamon extract, deliver coumarin in concentrations that may be considerably higher than those obtained from culinary use. The European Food Safety Authority (EFSA) has established a tolerable daily intake for coumarin of 0.1 mg per kilogram of body weight, and the FSA has issued consumer guidance advising caution with high or prolonged intake. Coumarin content varies widely between Cassia products, so it is not always possible to know the exact dose from a supplement label. Exceeding the tolerable daily intake regularly through high-dose supplements could, over time, carry a risk of liver toxicity in susceptible individuals.

If you are taking a cinnamon supplement regularly, be alert to possible signs of liver injury, which can include yellowing of the skin or whites of the eyes (jaundice), dark urine, persistent abdominal pain, or unusual fatigue. If you notice any of these symptoms, stop taking the supplement and seek prompt medical advice from your GP. If symptoms are severe, call 999 or attend your nearest A&E.

There is also a pharmacological interaction to be aware of. Cinnamon has demonstrated modest blood glucose-lowering properties in some studies. When combined with intermittent fasting, which itself reduces blood glucose and insulin levels, individuals taking medications for type 2 diabetes or insulin therapy may be at increased risk of hypoglycaemia. People taking sulfonylureas or insulin in particular should discuss any planned fasting protocol with their diabetes team before starting, as medication doses may need adjustment. Symptoms of low blood sugar include:

• Shakiness, sweating or palpitations

• Dizziness or light-headedness

• Confusion or difficulty concentrating

• Hunger or nausea

Anyone experiencing these symptoms should end their fast, consume a fast-acting carbohydrate (such as glucose tablets or a small glass of fruit juice) and contact their GP or diabetes team if symptoms persist or recur. Further guidance on recognising and managing hypoglycaemia is available from Diabetes UK and the NHS.

Regarding anticoagulant medicines: there are case reports in the medical literature of cinnamon supplements affecting INR in people taking warfarin, though the clinical evidence is limited. People taking warfarin should consult their anticoagulation service before starting any cinnamon supplement. A similar precaution is reasonable for those taking antiplatelet medicines such as clopidogrel, though the evidence here is less established.

People who are pregnant or breastfeeding should seek medical advice before using cinnamon supplements, as safety data in these groups are limited.

If you suspect you have experienced an adverse reaction to a herbal supplement or medicine, you can report this to the MHRA via the Yellow Card scheme at yellowcard.^[1][2]mhra.gov.uk.

What the current evidence says about cinnamon and metabolic health

Meta-analyses show cinnamon supplementation is associated with modest reductions in fasting blood glucose and total cholesterol, but study heterogeneity limits firm conclusions. NICE does not currently recommend cinnamon in diabetes or obesity guidelines.

The evidence on cinnamon and metabolic health is promising but not yet conclusive enough to support firm clinical recommendations. Several randomised controlled trials and meta-analyses have examined cinnamon's effect on fasting blood glucose, insulin sensitivity, lipid profiles and body weight, with mixed but generally modest positive findings.

A 2019 meta-analysis published in the journal Nutrients (Deyno et al., Nutrients 2019;11(8):1750) pooled data from multiple trials and found that cinnamon supplementation was associated with statistically significant reductions in fasting blood glucose and total cholesterol compared with placebo. However, the authors noted considerable heterogeneity between studies, including differences in cinnamon type, dose, duration and participant populations, which limits the strength of conclusions that can be drawn. More recent systematic reviews and meta-analyses published between 2022 and 2024 have broadly confirmed these modest effects on glycaemic and lipid outcomes, while continuing to highlight the variability in study quality and methodology.

The proposed mechanisms by which cinnamon may support metabolic health include:

• Improved insulin receptor sensitivity, potentially allowing cells to take up glucose more efficiently

• Inhibition of digestive enzymes such as alpha-amylase and alpha-glucosidase, which may slow carbohydrate absorption and blunt post-meal glucose spikes

• Anti-inflammatory effects, which may indirectly support metabolic function

These mechanisms are proposed on the basis of laboratory and clinical research, but their clinical relevance in everyday use varies and should not be overstated.

When considered alongside intermittent fasting, which has its own evidence base for improving insulin sensitivity and supporting weight management, the combination is theoretically complementary. However, there are no large, high-quality trials specifically examining cinnamon supplementation within an intermittent fasting protocol, so direct evidence for this combination remains limited.

NICE does not currently recommend cinnamon supplementation as part of any clinical guideline for diabetes management (NICE NG28) or obesity management (NICE NG246).^[7] Individuals should therefore view cinnamon as a potentially supportive dietary addition rather than a replacement for evidence-based interventions.

When to speak to a GP before combining cinnamon with fasting

People with diabetes, liver disease, or those taking warfarin, SGLT2 inhibitors or glucose-lowering medicines should consult their GP before combining cinnamon supplements with intermittent fasting. Pregnant or breastfeeding individuals should also seek medical advice first.

Certain individuals should speak to their GP before combining cinnamon supplementation with intermittent fasting, as the combination may not be appropriate for everyone. This is particularly important for people with pre-existing health conditions or those taking regular medication.

You should consult your GP before starting or continuing this combination if you:

• Have type 1 or type 2 diabetes, or are taking any glucose-lowering medication including metformin, sulfonylureas or insulin, due to the risk of hypoglycaemia

• Take SGLT2 inhibitors (such as dapagliflozin, empagliflozin or canagliflozin), as fasting can increase the risk of diabetic ketoacidosis in people taking this class of medicine; your prescriber should review your medication before you begin any fasting protocol^[8][9]

• Have a history of liver disease, given the potential hepatotoxic effects of high coumarin intake from Cassia cinnamon supplements

• Are taking anticoagulant medicines such as warfarin, as case reports suggest cinnamon supplements may affect INR; consult your anticoagulation service before starting

• Are taking antiplatelet medicines such as aspirin or clopidogrel, where the evidence for an interaction is limited but a precautionary discussion with your GP is reasonable

• Are pregnant or breastfeeding, as both high-dose cinnamon supplementation and prolonged fasting are generally not recommended during these periods

• Have a history of an eating disorder, as structured fasting protocols may not be appropriate and should only be undertaken with professional support; UK support is available through your GP, NHS eating disorder services, and the charity Beat (beateatingdisorders.org.uk)

• Experience recurrent dizziness, fatigue or palpitations during fasting windows, which may indicate that the protocol is not suitable for your individual physiology

If you develop symptoms that concern you during a fasting period, contact NHS 111 for urgent advice or see your GP at the earliest opportunity. Call 999 or attend A&E if symptoms are severe or life-threatening.

For those without contraindications, combining modest amounts of plain cinnamon with a sensible intermittent fasting approach is generally considered low risk. Nonetheless, personalised advice from a GP or registered dietitian remains the most reliable way to ensure any dietary change is appropriate for your individual health circumstances.

Scientific References

1. Herbal medicines: report suspected adverse reactions to the Yellow Card scheme.
2. Adverse reactions to drugs – BNF NICE.
3. Added Value to GLP-1 Receptor Agonist: Intermittent Fasting and Lifestyle Modification to Improve Therapeutic Effects and Outcomes.
4. Effects of intermittent fasting on metabolism in men.
5. Diabetes – NHS.
6. Diabetes – Type 2. British Dietetic Association.
7. Type 2 diabetes in adults: management (NG28).
8. SGLT2 inhibitors: updated advice on the risk of diabetic ketoacidosis.
9. A Novel Presentation of Euglycemic Diabetic Ketoacidosis Associated with SGLT2 Inhibitor and Weekly GLP-1 Agonist: Case Report.

Frequently Asked Questions