Cinnamon supplements for blood sugar: cassia vs Ceylon and label doses

Cinnamon supplements are usually cassia cinnamon, the type NCCIH says is most common in North America, and trials of cinnamon for blood sugar have used gram-level amounts, often 1 to 6 grams of powder a day. Many capsule labels list only tens of milligrams, and many never say which species is inside.

This guide explains the difference between cassia and Ceylon cinnamon, what the research used, why coumarin matters, and how to read a cinnamon line on a Supplement Facts panel.

What is the difference between cassia and Ceylon cinnamon?

Both come from the dried bark of Cinnamomum trees, but they are different species. NCCIH describes Ceylon cinnamon (Cinnamomum verum) as "true" cinnamon, grown primarily in Sri Lanka, and cassia cinnamon (Cinnamomum aromaticum) as the type grown in southeastern Asia that is the most common sold in North America.

	Ceylon cinnamon	Cassia cinnamon
Latin name	Cinnamomum verum	Cinnamomum aromaticum (also called C. cassia)
Where NCCIH says it grows	Primarily Sri Lanka	Southeastern Asia
Common in North America?	Less so	Most common type sold
Coumarin	May contain a trace amount	Contains varying amounts

NCCIH adds that cinnamon products may not clearly indicate which species or parts of the plant were used, and that the types and parts have important differences in chemical composition that can affect the product's impact on people. A label that just says "cinnamon" or "cinnamon bark" tells you very little.

What did cinnamon studies use?

NCCIH's summary of research on diabetes and supplements cites a 2019 review of 16 studies with 1,098 participants. It reported that cinnamon supplementation helped reduce fasting blood glucose and insulin resistance in people with prediabetes and type 2 diabetes. It also says the studies differed in strength of dose, length of treatment and type of participants, and that the review authors called for more research with standard cinnamon formulations.

The NCCIH page on cinnamon itself is more cautious. It says there have been many studies, especially for diabetes, but that the results are difficult to interpret because it is often unclear which species or part of the plant was tested. It concludes that research does not clearly support using cinnamon for any health condition, and that it is unclear whether cinnamon supplementation is helpful for diabetes or weight loss.

One of the most quoted trials is a 2003 study in Diabetes Care by Khan and colleagues. It divided 60 people with type 2 diabetes into six groups, three taking 1, 3 or 6 g of cinnamon a day and three taking matching placebo capsules, for 40 days. The abstract reported lower fasting glucose in all three cinnamon groups. There is an important caveat: the PubMed record for that paper now carries an expression of concern from the journal, dated September 2025. That is a good reason not to build a purchase decision on a single old trial that a sales page happens to quote.

What can be said with confidence is the range. In grams, the studies our reviews look at use 1 to 6 g of powder a day, or an extract equal to several grams of powder. That is the scale to keep in mind when reading a label.

How do label amounts compare with those doses?

A gram is 1,000 milligrams, and this is where the mismatch shows up. Here are examples from our reviews:

• The Blood Sugar Blaster review lists 50 mg of cinnamon bark powder. The trial that the page itself cites used a daily amount equal to about 3 g of cinnamon powder, so the label amount is roughly one sixtieth of the studied one. The review credits the page for disclosing individual amounts, which is unusual, but says the doses are far below the studies it cites.
• The RegenVive review lists a 4:1 cinnamon bark extract at 50 mg, described as roughly 200 mg of raw bark. The research on cinnamon and blood sugar typically used 1 to 6 g of powder, so even after the extract ratio is counted the amount is a fraction of the studied range.
• The Gluco6 review found cinnamon bark inside a 525 mg proprietary blend of seven ingredients, with no individual amounts. Cinnamon and gymnema both have human research, but not at a shared 525 mg dose.
• The GlucoTrust review lists cinnamon with no amount and no species.

Extract ratios such as "4:1" mean that a larger amount of raw material was used to make the smaller amount of extract. They are a fair way to state an amount, as long as the label also says which species and which part of the plant was used.

Why does coumarin matter?

Coumarin is a natural chemical in cassia cinnamon. NCCIH says interactions between coumarin and the liver have been reported. Consuming cassia cinnamon does not usually include enough coumarin to cause significant problems, but some cassia cinnamon products contain high levels, and prolonged use could be an issue for sensitive people, such as those with liver disease. NCCIH also says Ceylon cinnamon may contain a trace amount.

The diabetes summary from NCCIH adds two related points. Cinnamon supplementation at doses below 6 grams per day does not appear to pose a health risk, and the most common side effects at higher doses are allergic skin reactions and digestive problems. It also says that using herbal supplements such as cinnamon with conventional diabetes drugs can cause unwanted side effects, and that people who take diabetes drugs should tell their health care providers about any herbal supplements they use.

For any capsule that claims to use cinnamon at gram-level amounts, the species matters. If a label does not name it, you cannot judge coumarin exposure, and you cannot tell which type any study used. This is a transparency point that we score in each review.

What should you check on a cinnamon label?

1. The species. Look for "Cinnamomum verum" or "Ceylon" against "Cinnamomum aromaticum", "cassia" or "Chinese cinnamon". No species means no way to compare.
2. The part used. Bark, leaf and other parts differ in composition, according to NCCIH.
3. The amount per serving, and whether it is powder or an extract with a ratio.
4. The serving size. Cinnamon is often one of many ingredients, and the serving may be several capsules.
5. Whether it sits in a proprietary blend. The FDA says the amount per serving need not be declared for ingredients that are part of a proprietary blend.
6. Your medicines and health conditions. Ask a doctor or pharmacist, especially if you take diabetes medicine or have liver disease.

If you are comparing formulas, our blood sugar category shows how each offer handled cinnamon and the other ingredients.

Is a cinnamon supplement the same as cinnamon in food?

Not necessarily. NCCIH says cinnamon is likely safe when consumed in the amounts commonly used in foods as a spice or flavoring, and that larger amounts or long use are sometimes associated with gastrointestinal problems or allergic reactions. It also warns never to consume cinnamon powder as part of the "cinnamon challenge", an unsafe internet dare that can cause serious harm.

A capsule concentrates one ingredient, and a sales page may compare it with a spice on your shelf. The comparison does not say much either way, because the studies used specific products at specific amounts, and NCCIH says it is often unclear which species or part was tested.

FAQ

Does cinnamon lower blood sugar?

Research is mixed and hard to interpret. A 2019 review cited by NCCIH reported lower fasting glucose, but the studies differed in dose, length and participants, and the NCCIH cinnamon page says it is unclear whether cinnamon supplements help with diabetes. Talk with your doctor rather than relying on a sales page.

Which is safer, Ceylon or cassia cinnamon?

NCCIH notes that cassia cinnamon contains varying amounts of coumarin, which has been linked to liver effects in sensitive people, while Ceylon cinnamon may contain only a trace. That is a difference in coumarin, not a claim that one is better for any condition. A doctor can advise if you have liver disease.

How much cinnamon is in a capsule?

It varies widely. In our reviews the amounts range from 50 mg to blends with no stated amount, while studies used 1 to 6 g of powder a day. Check the panel for the amount, the form and the species.

Can I take cinnamon with diabetes medicine?

Ask your doctor or pharmacist before you do. NCCIH says that using herbal supplements such as cinnamon with conventional diabetes drugs can cause unwanted side effects.