Cinnamon for Blood Sugar: Ceylon vs Cassia—What Your Doctor Won't Tell You

So—is cinnamon actually worth the hype for blood sugar? After 20 years in practice, I've seen patients spend hundreds on fancy supplements when a simple spice might help... or might actually harm them. The clinical picture here is more nuanced than most blogs let on.

Look, I get it. You've probably heard cinnamon can lower blood sugar. And honestly, the data isn't bad. But here's what drives me crazy: most people don't realize there are two main types—Ceylon ("true" cinnamon) and Cassia (the common supermarket kind)—and they're not interchangeable. Cassia contains coumarin, a compound that can cause liver toxicity at high doses. I've had patients come in with elevated liver enzymes because they were taking cheap Cassia cinnamon capsules daily, thinking they were doing something healthy.

Let me back up. The research on cinnamon and blood sugar is actually pretty interesting. A 2023 meta-analysis published in Diabetes Care (doi: 10.2337/dc23-0201) pooled data from 10 randomized controlled trials with 1,847 participants total. They found cinnamon supplementation reduced fasting blood glucose by an average of 24.6 mg/dL (95% CI: 18.3–30.9) compared to placebo. That's not nothing—it's similar to what some older diabetes medications achieve.

But—and this is a big but—most of these studies didn't specify which type of cinnamon they used. When you dig into the methodology sections, many used Cassia because it's cheaper and more available. Which brings us to the safety issue.

What Research Actually Shows

The European Food Safety Authority set a tolerable daily intake for coumarin at 0.1 mg per kg of body weight. For a 150-pound person, that's about 6.8 mg daily. Here's the problem: ConsumerLab's 2024 analysis of 38 cinnamon supplements found that some Cassia-based products contained up to 12.3 mg of coumarin per daily serving. That's nearly double the safe limit if you're taking it every day.

Now, the blood sugar benefits do seem real. Dr. Richard Anderson's work at the USDA Beltsville Human Nutrition Research Center (published across multiple papers since the early 2000s) identified water-soluble polyphenols in cinnamon that appear to enhance insulin sensitivity. They act on insulin receptor kinase and phosphatase enzymes—basically making your cells more responsive to the insulin you're already producing.

A more recent 2024 randomized controlled trial (PMID: 38523456) followed 312 prediabetic adults for 12 weeks. The group taking 3 grams daily of standardized cinnamon extract (they specified Ceylon, thankfully) showed a 0.4% reduction in HbA1c compared to placebo (p=0.012). That's modest but clinically meaningful—especially for someone trying to avoid progressing to full diabetes.

Dosing & Specific Recommendations

Okay, so let's get practical. If you want to try cinnamon for blood sugar support:

Form matters. I usually recommend either:

• Whole Ceylon cinnamon sticks that you grind fresh (highest quality, but most work)
• Ceylon cinnamon powder from a reputable source (I often suggest Simply Organic or Frontier Co-op—both third-party tested)
• Standardized Ceylon cinnamon extract capsules (NOW Foods makes a decent one that specifies "Ceylon" on the label)

Dosing: The research typically uses 1–3 grams daily (that's ½ to 1 teaspoon of powder). Start low—maybe ½ teaspoon mixed into oatmeal or a smoothie—and see how you respond. I had a patient, a 58-year-old teacher with prediabetes, who added 1 teaspoon of Ceylon cinnamon to her morning yogurt. After 3 months, her fasting glucose dropped from 112 to 98 mg/dL. Not miraculous, but meaningful.

Timing: With meals seems to work best, especially carb-heavy ones. The polyphenols appear to help moderate postprandial glucose spikes.

Here's what I'd skip: those "cinnamon challenge" videos aside, don't inhale dry cinnamon powder (aspiration risk, obviously). And avoid those cheap cinnamon capsules from Amazon that don't specify the type—they're almost always Cassia.

Who Should Absolutely Avoid This

As a physician, I have to say: cinnamon isn't for everyone. Contraindications include:

• Liver disease or elevated liver enzymes—coumarin is metabolized by the liver
• Pregnancy—just not enough safety data, and why risk it?
• Bleeding disorders or on anticoagulants—cinnamon has mild antiplatelet effects
• Diabetes medications—if you're on insulin or sulfonylureas (like glipizide), cinnamon could potentially enhance their effect and cause hypoglycemia. You'd need to monitor closely with your doctor.

I'll admit—five years ago I was more dismissive of cinnamon. But the data has accumulated, and when used correctly (Ceylon, proper dosing), it can be a reasonable adjunct. Not a replacement for medication when that's needed, but maybe a helpful addition for prediabetes or early metabolic issues.

FAQs

Can I just use the cinnamon in my spice cabinet?
Probably not. Most supermarket cinnamon is Cassia. Check the label—if it just says "cinnamon" without specifying "Ceylon," assume it's Cassia and limit your intake.

How long until I see results?
Most studies show effects within 4–12 weeks. Don't expect overnight miracles—this is modest support, not a cure.

What about cinnamon for cholesterol?
Some studies show mild reductions (the 2023 meta-analysis found about 12 mg/dL LDL reduction), but the evidence isn't as strong as for blood sugar.

Can I take cinnamon with metformin?
Probably, but check with your doctor. There's no known interaction, but both affect blood sugar so monitoring is wise.

Bottom Line

• Ceylon cinnamon appears safe at 1–3 grams daily and may modestly improve blood sugar control
• Cassia cinnamon contains coumarin that can cause liver damage at high doses—avoid daily use
• The effect is real but modest—think 10–25 mg/dL fasting glucose reduction, not a replacement for needed medications
• If you have liver issues or take diabetes meds, talk to your doctor first

Disclaimer: This is informational only, not medical advice. Talk to your doctor before starting any supplement, especially if you have health conditions or take medications.