The evidence file
One spice. Two kinds of bark. One honest page.
You have probably been let down by a supplement before. So instead of asking you to trust us, this page shows you the actual studies behind cinnamon and blood sugar — the doses, the sample sizes, the results, the places where the research still falls short, and why we only use Ceylon.
Start here
Your skepticism is the correct starting position
Most cinnamon capsules do very little. That is not cynicism — it is the predictable result of how they are made.
The cinnamon in most of them is cassia: cheap, widely available, and according to the NIH the most common type sold in the United States and Canada. It is also the type that carries meaningful amounts of coumarin. Proprietary blends let a brand put cinnamon next to four other ingredients while disclosing only one combined total. And a great deal of what gets sold as science is a test-tube result dressed up as a clinical finding.
If you have already tried cinnamon pills and seen nothing change, the reasonable conclusion is not that your body is unusual. It is that you were probably given an unknown amount of the wrong bark.
So the useful question is not whether a supplement sounds scientific. It is three plain things: what was actually tested, at what dose, and in how many people. That is what the rest of this page answers.
The ledger
How strong is the evidence, measure by measure
Cinnamon is one ingredient, but it has been tested against several different measures — and the evidence is not equally strong for all of them. Rather than call everything "clinically studied," here is our own reading of the human trials, including where it is weak.
Cinnamon
Fasting blood sugar
Two separate meta-analyses of randomised trials — 10 trials in 2013, 16 trials in 2019 — both found lower fasting glucose with cinnamon. The size of the effect varies a great deal from study to study.
Cinnamon
Insulin resistance
The 16-trial analysis found improved insulin resistance scores (HOMA-IR). Fewer trials measured it, and they did not always agree. Promising, not settled.
Cinnamon
Cholesterol & triglycerides
The 2013 analysis found lower total cholesterol, LDL and triglycerides. The 2019 analysis found no significant change in blood lipids. Mixed — so we do not lean on it.
Cinnamon
HbA1c (3-month average)
Neither meta-analysis found a significant change in HbA1c. A 2025 placebo-controlled trial of a Ceylon extract made it a primary outcome and reports a reduction — one trial is a start, not a consensus.
Mechanism
Why cinnamon — and why only Ceylon
Cinnamon is not just a flavour. Its bark carries compounds researchers have studied for decades — and the two main kinds of cinnamon differ in one compound that matters a great deal.
Two barks, one name
Ceylon cinnamon — Cinnamomum verum, "true" cinnamon — grows in Sri Lanka. Its bark is thin and rolled in many fine layers. Cassia is harder, darker and cheaper, and it is what most cinnamon on a US shelf actually is. Both are sold under the same word.
A slower rise after a meal
In a 2007 study in the American Journal of Clinical Nutrition, adding 6 g of cinnamon to a rice pudding slowed how quickly the stomach emptied and blunted the rise in blood sugar afterwards, in 14 healthy adults. Slower emptying means sugar reaches the blood more gradually.
Polyphenols studied for insulin signalling
Researchers at the US Department of Agriculture isolated polyphenol compounds from cinnamon bark that increased insulin-dependent glucose metabolism in cell cultures. That is a laboratory finding, not proof of an effect in people — it is the reason human trials were run at all.
The coumarin difference
Cassia contains coumarin, a natural compound that in larger amounts can strain the liver of sensitive people. Germany's Federal Institute for Risk Assessment puts cassia at around 3,000 mg of coumarin per kilogram on average. Ceylon contains only traces. For something taken every day, that difference is the whole decision.
The trials
The four studies worth actually reading
Every source is linked in full at the bottom of this page. Read them yourself — that is rather the point.
Meta-analysis · 10 trials
Cinnamon and type 2 diabetes
Allen and colleagues, Annals of Family Medicine, 2013. An updated systematic review of randomised trials.
- Design
- Systematic review and meta-analysis
- Participants
- 543 adults with type 2 diabetes
- Doses
- 120 mg to 6 g of cinnamon per day
- Duration
- 4 to 18 weeks
No significant effect on HbA1c. Cinnamon type and dose varied widely between the trials.
Meta-analysis · 16 trials
Type 2 diabetes and prediabetes
Deyno and colleagues, Diabetes Research and Clinical Practice, 2019. A broader and more conservative read than any single trial.
- Design
- Meta-analysis and meta-regression
- Trials
- 16 randomised controlled trials
- Population
- Type 2 diabetes and prediabetes
No significant change in HbA1c or blood lipids. The authors flag high variability between the included studies.
RCT · double-blind · placebo
Ceylon extract, 210 adults
University of Colombo trial, Diabetes & Metabolic Syndrome, 2025. One of very few trials run on Ceylon specifically.
- Design
- Double-blind, placebo-controlled
- Participants
- 210 adults with type 2 diabetes
- Doses
- 250 mg or 500 mg Ceylon extract a day
- Duration
- 4 months (registered protocol)
Good tolerability, no serious adverse events reported. We are not quoting effect sizes until we can point you to the full figures.
Crossover · single meal
Cinnamon and the after-meal rise
Hlebowicz and colleagues, American Journal of Clinical Nutrition, 2007. Small, but it shows a mechanism clearly.
- Design
- Crossover, measured by ultrasound
- Participants
- 14 healthy adults
- Dose
- 6 g of cinnamon with a rice pudding
A single meal in healthy people at a large culinary dose. It shows a mechanism, not a daily-use result.
The other half
What this research does not show
Any brand can quote its best study. Here are the limitations we would want to know about if we were the one reading — and they are the reason we describe cinnamon as support rather than treatment.
- Most trials did not use CeylonMuch of the cinnamon research was run on cassia or did not name the species at all. A European Medicines Agency assessment noted that only a small number of the clinical studies used Ceylon cinnamon. The 2025 Ceylon-extract trial matters precisely because it is rare.
- The results vary a lotBoth meta-analyses report high heterogeneity — the trials disagree with each other more than anyone would like. Different species, doses, durations and populations make one clean number impossible.
- HbA1c has not moved in the pooled dataNeither meta-analysis found a significant change in HbA1c, the three-month average your doctor tracks. One newer Ceylon trial reports a reduction. One trial is a start, not a settled answer.
- The trials are shortFour weeks to four months, in most cases. What that tells you about years of daily use is genuinely unknown.
- Our softgel has not been trialled as a finished productThe studies on this page tested cinnamon or cinnamon extracts. None of them tested Metabella's softgel itself, and we are not going to imply they did.
- This is not a diabetes treatmentCinnamon is studied as support for healthy blood sugar, not as a replacement for medication. If you take metformin, insulin or anything else for blood sugar, nothing on this page is a reason to change it.
Dose transparency
Research is worthless if the dose is hidden
Under US labelling rules, a brand may group several ingredients into a "proprietary blend" and disclose only the combined total. The ingredients are listed in descending order by weight, but no individual amount appears. A blend can be almost entirely one cheap ingredient with traces of the ones named on the front.
A typical proprietary blend
One number, five ingredients
- 850 mg Metabolic Support Blend
- Cinnamon bark (species not stated)
- Chromium
- Bitter melon
- Banaba leaf
- Alpha lipoic acid
You cannot tell how much cinnamon is in it, or whether it is cassia. That is the feature, not the flaw.
Metabella Ceylon
Every number on the front
- 600 mg Ceylon cinnamon extract, concentrated 12:1
- 7,200 mg Raw Ceylon bark equivalent per softgel
- 1 Softgel a day, taken with a meal
12:1 means twelve parts of raw Ceylon bark go into one part of extract. We suspend it in MCT oil from coconut instead of pressing dry powder into a capsule, because many of cinnamon's aromatic compounds are oil-soluble. That is our formulation reasoning, not a clinical claim.
What to expect
This builds. It does not switch on.
In the trials above, cinnamon was taken every day for four weeks at the shortest and four months at the longest. Anyone promising you a first-week transformation is selling something other than cinnamon.
Week 1–2
Nothing dramatic, and that is normal
One softgel with a meal. The only thing that matters in this stretch is that the habit sticks — the research is built on daily use, not occasional use.
Week 3–4
The earliest point anything was measured
The shortest trials in the meta-analyses ran four weeks. If you like to compare numbers, this is a sensible moment to have had a baseline taken.
Week 5–12
Where much of the trial data sits
Many of the cinnamon trials ran for around twelve weeks of daily use. This is the stretch where consistency counts most.
Month 3–4
The Ceylon trial's territory
The 2025 placebo-controlled Ceylon trial ran four months. Our ninety-day guarantee is set deliberately long enough to cover a fair trial of your own.
Safety
Read this part before you order
Most people over fifty are taking something else. Cinnamon was generally well tolerated in the trials — mild digestive upset is the most commonly reported effect — but it is biologically active, and that cuts both ways.
Speak to your doctor before starting if any of the following apply
- Metformin, insulin or other blood sugar medication. Cinnamon may add to their effect, so blood sugar could drop further than intended. Keep monitoring as usual.
- A liver condition. Ceylon contains only traces of coumarin, but if your liver is already under strain, every supplement deserves a conversation first.
- Pregnancy or breastfeeding. There is not enough research on concentrated cinnamon extracts in pregnancy. Ask first.
- Several prescriptions at once. Worth raising with whoever manages them.
Coumarin in context: Germany's Federal Institute for Risk Assessment sets the tolerable daily intake at 0.1 mg per kilogram of body weight. About 2 g of cassia a day can already reach that for a 60 kg (132 lb) adult. Ceylon contains only traces — which is why it is the only cinnamon we use.
You have read the evidence. Including the gaps.
True Ceylon cinnamon from Sri Lanka, concentrated 12:1 — 600 mg of extract, the equivalent of 7,200 mg of bark — pre-dissolved in MCT oil. One softgel a day, every number printed on the pouch.
90-day money-back guarantee · Easy returns
References
Every source, linked
Cinnamon and blood sugar
- Allen R.W. et al. Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis. Annals of Family Medicine 2013;11(5):452–459. pubmed.ncbi.nlm.nih.gov/24019277
- Deyno S. et al. Efficacy and safety of cinnamon in type 2 diabetes mellitus and pre-diabetes patients: a meta-analysis and meta-regression. Diabetes Research and Clinical Practice 2019;156:107815. pubmed.ncbi.nlm.nih.gov/31425768
- Randomised, double-blind, placebo-controlled trial of Cinnamomum zeylanicum (Ceylon cinnamon) extract in type 2 diabetes. Diabetes & Metabolic Syndrome: Clinical Research & Reviews 2025. pubmed.ncbi.nlm.nih.gov/41412108
- Ranasinghe P. et al. Cinnamomum zeylanicum (Ceylon cinnamon) as a potential pharmaceutical agent for type-2 diabetes mellitus: study protocol for a randomized controlled trial. Trials 2017. doi.org/10.1186/s13063-017-2192-0
- Sri Lanka Clinical Trials Registry, SLCTR/2017/010. slctr.lk/trials/slctr-2017-010
- Translating traditional knowledge into clinical evidence: the journey of Ceylon cinnamon. JCCP 57(1). jccp.sljol.info/articles/8197
Mechanism
- Hlebowicz J. et al. Effect of cinnamon on postprandial blood glucose, gastric emptying, and satiety in healthy subjects. American Journal of Clinical Nutrition 2007;85(6):1552–1556. pubmed.ncbi.nlm.nih.gov/17556692
- Anderson R.A. et al. Isolation and characterization of polyphenol type-A polymers from cinnamon with insulin-like biological activity. Journal of Agricultural and Food Chemistry 2004;52(1):65–70. Summary by the USDA: ars.usda.gov
Species, coumarin and safety
- German Federal Institute for Risk Assessment (BfR). FAQ on coumarin in cinnamon and other foods. bfr.bund.de
- NIH, National Center for Complementary and Integrative Health. Cinnamon. nccih.nih.gov/health/cinnamon
- NIH, National Center for Complementary and Integrative Health. Diabetes and dietary supplements. nccih.nih.gov/health/diabetes-and-dietary-supplements
- European Medicines Agency. Assessment report on Cinnamomum verum J.S. Presl, cortex (addendum). ema.europa.eu
Population context
- CDC National Diabetes Statistics Report. cdc.gov/diabetes/php/data-research
Metabella · Ceylon Cinnamon 7200mg Equivalent with MCT Oil
This page describes published research on cinnamon and cinnamon extracts. It is not a description of a clinical trial of the finished product. Individual results vary, and the studies cited were conducted in defined populations under defined conditions that may not resemble your own.
These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.
Nothing here is medical advice, and it is not a reason to start, stop, or change a prescription. If you take medication for blood sugar, or have a liver condition, speak with your doctor before beginning any supplement.