C8 and C10 are two specific fatty acids found in MCT oil. C8 is caprylic acid, a fat with an 8-carbon chain. C10 is capric acid, with a 10-carbon chain. These two fatty acids are the reason MCT oil works differently from regular fats: their short chains allow them to skip the normal fat-digestion process and reach your liver almost immediately, where they’re converted into quick energy or ketones.
How C8 and C10 Differ From Other Fats
Most dietary fats are long-chain triglycerides with 14 to 20 carbon atoms. When you eat these fats, they get repackaged inside your intestinal cells, bundled into particles called chylomicrons, and routed through your lymphatic system before eventually reaching your bloodstream. This is a slow, multi-step process.
C8 and C10 take a shortcut. Because their carbon chains are so short, they’re broken down into individual fatty acids in the gut and absorbed directly into the portal vein, the blood vessel that leads straight to the liver. Once there, the liver rapidly breaks them down for energy or converts them into ketones. This is why people feel a fast energy boost from MCT oil compared to, say, olive oil or butter.
C8: The Stronger Ketone Producer
If your main goal with MCT oil is raising ketone levels, C8 is the clear winner. The ketogenic effect of C8 is roughly three times higher than C10 and six times higher than C12 (lauric acid, the main fat in coconut oil). One study found that plasma ketone levels rose for about four hours after consuming C8, while C10 produced no significant ketone increase at all.
This is why many MCT oil brands market “pure C8” products at a premium. For people following a ketogenic diet or using MCT oil specifically for mental clarity tied to ketone production, a C8-dominant oil delivers more of what they’re looking for per tablespoon.
C10: Slower but Still Useful
C10 doesn’t produce ketones as efficiently, but it still follows the same rapid-absorption pathway to the liver. It contributes to quick energy availability and shares many of the general metabolic benefits of medium-chain fats, including supporting insulin sensitivity and promoting satiety. Research in animal models suggests medium-chain fatty acids like C10 can increase beneficial gut bacteria populations and stimulate anti-inflammatory effects.
C10 is also typically less expensive to produce than isolated C8, which is one reason many MCT oils contain a blend of both. A common ratio is 60% C8 to 40% C10, though this varies by brand.
Why Most MCT Oils Exclude C12
Technically, there are four medium-chain fatty acids: C6 (caproic acid), C8, C10, and C12 (lauric acid). But quality MCT oils are formulated around C8 and C10 specifically, and here’s why.
C6 is effective but tastes harsh and can cause stomach discomfort, so it’s typically removed during processing. C12, lauric acid, is the dominant fatty acid in coconut oil, making up about half its fat content. Although C12 has 12 carbon atoms and technically qualifies as a medium-chain fat, it behaves more like a long-chain fat during digestion. Most of it gets routed through the lymphatic system rather than the portal vein. This means coconut oil and MCT oil are not interchangeable. Coconut oil delivers mostly C12 with slow absorption, while MCT oil delivers concentrated C8 and C10 with fast absorption.
How Your Body Handles MCT Oil
The most common side effect of MCT oil is digestive upset: cramping, diarrhea, or nausea. In one clinical trial, 64% of reported side effects were gastrointestinal. The good news is that these symptoms typically resolve by reducing the dose, and in the study, none were severe enough to make participants stop using the oil entirely.
Starting with one tablespoon (about 14 grams) per day and gradually increasing over several weeks is a well-tested approach. In that same trial, participants titrated from one tablespoon daily up to three tablespoons (about 42 grams) daily over several weeks. Long-term use at that maximum dose showed no adverse effects on blood lipid levels, body fat composition, or blood sugar metabolism.
If you experience stomach trouble, cutting back to a smaller amount and mixing it into food rather than taking it straight often helps. Your digestive system generally adapts within a week or two.
Using MCT Oil in the Kitchen
MCT oil has a smoke point between 280°F and 320°F (138°C to 160°C), depending on purity. That’s lower than coconut oil at 350°F and well below what you’d need for frying, searing, or high-heat sautéing. Heating it above its smoke point degrades the fatty acids and reduces the oil’s benefits.
Where MCT oil works well is in preparations that don’t involve high heat: blended into coffee, drizzled over salads, stirred into smoothies, or mixed into sauces after cooking. You can use it for gentle warming, like low-temperature baking or adding to warm oatmeal, but it’s not a substitute for your go-to cooking oil.
Choosing Between C8, C10, or a Blend
Your choice depends on what you’re using MCT oil for. If you want maximum ketone production for a keto diet or cognitive focus, a pure C8 oil is the most efficient option per serving. If you’re using MCT oil as a general energy source and want to keep the cost lower, a C8/C10 blend gives you most of the benefits at a better price point. There’s no strong evidence that pure C10 oil offers advantages over a blend, so standalone C10 products are uncommon.
Regardless of the ratio, look for oils that list only caprylic acid and capric acid (or “C8” and “C10”) on the label. If coconut oil or lauric acid appears as a primary ingredient, you’re getting a product that’s closer to coconut oil than true MCT oil.