A gelatin capsule is a small, digestible shell made primarily from animal-derived protein, designed to hold medication, supplements, or other active ingredients for oral consumption. It dissolves in your stomach within about 7 to 12 minutes depending on whether you’ve eaten recently, releasing its contents for absorption. Gelatin capsules are the most common delivery format in both prescription drugs and over-the-counter supplements worldwide.
What Gelatin Is Made From
Gelatin itself is not found in nature. It’s produced by breaking down collagen, the structural protein in animal connective tissue. Manufacturers extract it primarily from pig skin and cattle hides and bones through a process of prolonged boiling and chemical hydrolysis. The result is a mixture of water-soluble proteins with a high average molecular weight, composed mainly of the amino acids glycine (about 25.5%), proline (18%), and hydroxyproline (14%).
Fish gelatin has emerged as an alternative source, largely driven by religious dietary restrictions that prohibit pork or beef consumption. However, porcine and bovine sources still dominate the market because of their abundance and lower cost.
What’s Inside the Shell
The capsule shell is more than just gelatin. In a standard formulation, gelatin accounts for roughly 40 to 45% of the shell by weight. Water makes up 30 to 40% during manufacturing but drops to 4 to 10% in the finished product. The rest consists of plasticizers, which keep the shell flexible rather than brittle. Glycerin is the most common plasticizer, though sorbitol, xylitol, and several others are also used.
Colorants are added at about 0.5 to 1% to change the capsule’s appearance. These can be synthetic dyes like brilliant blue or tartrazine, or natural options like curcumin, riboflavin, and annatto. Some capsules also include opacifiers, flavors, sweeteners, or preservatives to prevent fungal growth.
Hard Capsules vs. Softgels
Gelatin capsules come in two fundamentally different designs. Hard gelatin capsules are the familiar two-piece shells with a body and a cap that fit together. They come in a range of standardized sizes, from the largest (size 000) down to the smallest (size 5), and typically hold powders, granules, or pellets. Their shells contain 13 to 16% water, giving them a firm but slightly flexible feel.
Soft gelatin capsules, commonly called softgels, are one-piece shells with thicker, more globular walls. They’re heavily plasticized with glycerin or sorbitol, which gives them their characteristic chewable, flexible texture. Softgels are designed to hold liquids or oil-based formulations, which is why you’ll often see them used for fish oil, vitamin E, and similar supplements. They require large-scale production methods and tend to cost more to manufacture than hard capsules. One trade-off with softgels is that the active ingredient can sometimes migrate into the shell itself over time.
How They’re Manufactured
Hard gelatin capsules are made through a dipping process. First, pharmaceutical-grade gelatin is dissolved in purified water heated to 60 to 70°C, creating a thick solution of about 30 to 40% gelatin by weight. A vacuum is applied to remove air bubbles that would cause defects.
Metal pins are then dipped into this solution, coating them in a thin, even layer. The coated pins pass through a drying furnace where temperature and humidity are carefully controlled to remove moisture without cracking the shell. Once dry, the capsule halves are stripped from the pins, trimmed to precise lengths, and the two pieces are loosely joined together for shipping. The capsules arrive at pharmaceutical or supplement companies as empty shells, ready to be filled with their intended contents.
How Gelatin Capsules Dissolve
On an empty stomach, a standard gelatin capsule disintegrates in roughly 7 minutes. If you’ve recently eaten, that time extends to about 12 minutes because food in the stomach buffers the capsule from direct contact with gastric fluid. This relatively fast dissolution is one of the main reasons gelatin has remained the dominant capsule material for decades. Once the shell breaks apart, the contents are exposed to stomach acid and digestive enzymes, and absorption begins.
Plant-Based Alternatives
The main competitor to gelatin capsules is HPMC (hydroxypropyl methylcellulose), a plant-derived polymer made from cellulose. These capsules are suitable for vegetarians, vegans, and people who avoid animal products for religious reasons. In terms of dissolution, the two perform similarly: HPMC capsules break down in about 8 minutes on an empty stomach and 16 minutes after a meal, with no statistically significant difference from gelatin.
Where the two materials differ most is in how they handle moisture. Gelatin capsules start with a higher water content (10 to 14%) and absorb moisture slowly but steadily, eventually softening and losing puncture resistance. HPMC capsules contain only 4 to 6% water initially and adapt to humidity changes more dynamically at the molecular level. They retain better mechanical integrity after moisture exposure and recover faster from environmental stress. This makes HPMC capsules a better choice for moisture-sensitive ingredients.
Gelatin capsules do have higher initial strength and puncture resistance when stored properly. But that advantage erodes quickly in humid conditions. If you’ve ever found a bottle of old supplements where the capsules became sticky or rubbery, that’s gelatin absorbing too much moisture from the air.
Storing Gelatin Capsules Properly
Gelatin capsules perform best when stored at 15 to 25°C (roughly 59 to 77°F) and 35 to 65% relative humidity. Under these conditions, their moisture content stays in the optimal 13 to 16% range. When moisture drops below 13%, the shells become increasingly brittle and can crack or shatter when you try to swallow them or press them out of blister packs. On the other end, excess humidity makes them sticky and soft, causing them to cling to surfaces and dissolve unevenly.
In practical terms, this means keeping your capsules in a cool, dry place and out of the bathroom, where heat and steam from showers can accelerate degradation. Keeping the original container tightly closed, especially if it includes a desiccant packet, helps maintain the right moisture balance.