What Are Pill Capsules Made Of

The supplement and pharmaceutical industries consume well over a trillion empty capsules every year, and most buyers spend nearly all their time thinking about what goes inside them—the powder blend, the dosage, and the release profile. The shell itself often gets treated as a commodity. It isn’t. What a capsule is made from decides how fast it dissolves in the stomach, how it behaves on a high-speed filling line, and whether your finished product stays stable for two years or starts cracking in six months.

Most pill capsules are made of gelatin or hypromellose (HPMC). Gelatin shells use animal-derived collagen, usually from bovine or porcine sources, while HPMC shells are made from plant-based cellulose. Both materials are mixed with purified water and small amounts of additives—colorants, opacifiers, and gelling agents—before being molded into the two-piece shells used across the industry.

Below, we break down each shell material, the other ingredients that go into a capsule, and why this choice matters long before your production run starts.

What are the main materials used in pill capsules?

Hard, two-piece capsules come in two materials that cover the vast majority of the market: gelatin and HPMC. A third option, pullulan, serves a smaller niche. Soft capsules are a different format altogether and use a plasticized gelatin shell. Here’s how each one works.

Gelatin capsules

Gelatin has been the standard capsule material for more than a century. It’s produced by partially hydrolyzing collagen extracted from bovine hides and bones or porcine skin. Manufacturers classify it into two types:

• Type A gelatin comes from acid-treated pork skin. It has an isoelectric point between pH 7 and 9.
• Type B gelatin comes from alkali-treated bovine collagen. Its isoelectric point sits between pH 4.7 and 5.4.

Gelatin shells dissolve fast — usually within 10 to 20 minutes in gastric fluid — and they’re the cheapest option per thousand units. They run well on almost every filling machine ever built. The downside is moisture sensitivity: gelatin shells hold 13% to 16% water, and they turn brittle when that drops below about 12%.

HPMC capsules

HPMC (hypromellose, or hydroxypropyl methylcellulose) is a semi-synthetic polymer made from plant cellulose. It appeared as a commercial capsule material in the 1990s and has taken a growing share of the market since.

HPMC shells contain only 4% to 6% moisture, so they stay flexible in dry conditions where gelatin would crack. They also suit hygroscopic fills — powders that pull water out of a gelatin shell and make it brittle. Vegan, halal, and kosher positioning comes built in, since no animal material is involved.

The trade-offs are a higher unit price and slightly slower dissolution in some formulations. Older HPMC shells also needed gelling agents to form properly, though newer gelling-agent-free grades have largely solved that.

Pullulan and soft gelatin capsules

Pullulan is a water-soluble polysaccharide made by fermenting starch. It’s fully natural, odorless, and has excellent oxygen barrier properties, which makes it a particularly suitable fit for oxidation-sensitive ingredients. Cost keeps it a niche product.

Soft gelatin capsules — the kind used for fish oil and vitamin E — are one-piece shells of gelatin plasticized with glycerin or sorbitol. The plasticizer is what makes them soft and elastic enough to hold liquid fills.

What else goes into a capsule shell?

A capsule shell is never just gelatin or just HPMC. The base polymer is the bulk of it, but a working shell formula includes several supporting ingredients, each doing a specific job.

Purified water is the largest secondary component. It acts as the processing medium during manufacturing and remains in the finished shell as residual moisture—the 13–16% in gelatin that keeps it flexible.

Colorants give capsules their appearance and help with product identification. Iron oxides and synthetic dyes are the common choices. Titanium dioxide served for decades as the standard white pigment and opacifier, protecting light-sensitive fills. The EU banned TiO₂ as a food additive (E171) in 2022, and while pharmaceutical use is still permitted, many manufacturers have already moved to alternatives like calcium carbonate or rice starch-based opacifiers.

Gelling agents appear mostly in HPMC capsules. Traditional HPMC formulas need carrageenan or gellan gum to gel on the molding pins. Newer thermogelation grades skip them entirely.

Preservatives like parabens used to be standard but have largely disappeared from modern formulas, since controlled moisture and effective manufacturing hygiene do the job instead.

Every one of these ingredients falls under regulatory oversight. In the US, capsule shell components must be listed in the FDA’s Inactive Ingredient Database or have GRAS status, and gelatin sourcing must follow TSE/BSE rules that require documented, BSE-free animal origins. A reputable shell supplier will provide this documentation without you having to ask twice.

How are empty capsules manufactured?

Hard capsules are made by a dip-molding process that hasn’t changed much in principle since the 1940s, even though the machinery has gotten far more precise. The basic sequence:

1. Dipping. Stainless steel molding pins, machined to exact capsule dimensions, are dipped into a temperature-controlled gelatin or HPMC solution.
2. Gelling and drying. The film on the pins sets, then moves through a series of drying kilns where temperature and humidity are tightly controlled. This step fixes the shell’s final moisture content.
3. Stripping and trimming. Dried shells are pulled off the pins and cut to length. Cap and body are made on separate pin sets.
4. Joining and printing. Caps and bodies are pre-joined for shipping, and shells may be printed or banded.
5. Quality control. Shells are checked for dimensions, wall thickness, moisture, and visual defects before packing.

The environment matters as much as the machines. Production rooms typically hold 20–25°C and 35–45% relative humidity, because a few points of humidity swing will change drying time, wall thickness, and final moisture. That moisture level follows the shells into your warehouse, which is why storage conditions for empty capsules — cool, dry, sealed — directly affect how they run months later.

Dimensional consistency is the other quiet variable. A capsule that runs a few microns off spec will feed poorly, separate badly, or fail to lock after filling. Buyers who shop shells on price alone usually discover these issues on the filling line, at full speed, at the worst possible time.

Why does shell material matter on the filling line?

Shell material determines how capsules behave inside your capsule filler — how cleanly caps and bodies separate, how the shells handle vacuum and mechanical force, and how many rejects you get per shift. Two capsules that look identical in a sample bottle can perform very differently at 90,000 capsules per hour.

Common shell-related problems on a capsule filler

A modern automatic capsule filler compensates for a lot—controlled vacuum for cap separation, precise dosing stations, gentle closing force—but it can’t fix a bad shell lot. The machines that run best are the ones fed with consistent, correctly stored capsules matched to the fill material.

Matching shell to machine and batch size

Scale changes the calculation too. On a fully automatic capsule filler machine running six-figure batches, small shell defects multiply into real money, so shell quality and machine compatibility dominate the decision. At the other end, a lab doing formulation work with a manual capsule filler tray, or a small brand hand-filling with a capsule filler kit, cares more about how the shell handles and whether it suits the ingredient than about line speed.

What doesn’t change with scale: brittle shells crack, soft shells deform, and static-prone shells misfeed. If you’re experiencing these problems, the shell is usually the first place to look—and switching material is often cheaper than fighting the symptoms.

How do you choose the right capsule material for your product?

Work from your fill formula outward. The right shell is the one that keeps your specific ingredient stable and delivers it the way you promised on the label.

1. Check hygroscopicity. If your powder pulls moisture from the air, it will pull it from a gelatin shell too. HPMC, with its 4–6% moisture content, is the safer home for hygroscopic fills.
2. Screen for aldehydes. Aldehyde-containing ingredients and some preservatives trigger cross-linking in gelatin—a reaction that toughens the shell and slows or blocks dissolution. HPMC doesn’t cross-link.
3. Match the fill format. Oils and pastes belong in soft gelatin or sealed HPMC shells. Standard dry powders run fine in either hard or soft capsules.
4. Confirm dietary positioning. Porcine gelatin rules out halal and kosher markets. Bovine gelatin works with proper certification. HPMC and pullulan support vegan claims without requiring paperwork gymnastics.
5. Test dissolution early. Run your fill in both shell types before you commit. A 15-minute difference in disintegration can matter for fast-acting products.
6. Cost it honestly. HPMC costs more per unit. Weigh that against reject rates, stability failures, and the markets you can’t enter with animal gelatin.

A supplier that understands both capsules and filling equipment can shortcut a lot of the process. Send your formula details and target markets, and ask for a shell recommendation with the reasoning behind it—if a supplier can’t explain the why, keep looking.

What happens after filling? Polishing and inspection

Filled capsules leave the dosing station with powder dust on the outside and, occasionally, defects you can’t afford to ship. Two downstream steps handle these issues.

A capsule polisher removes surface dust using rotating brushes and vacuum extraction, often combined with empty-capsule rejection and metal detection in a single pass. Clean capsules aren’t a cosmetic nicety — dust on the shell surface interferes with downstream coating, printing, and blister sealing, and it’s a basic GMP expectation. If you’re running medium or high volumes, a dedicated capsule polisher pays for itself quickly in reduced complaints and cleaner packaging runs.

Visual defects are the other filter. You need to catch cracked shells, oil spots, dents, color variation, and foreign particles before bottles leave the building. Manual sorting works at a small scale, but it misses things at line speed, and tired eyes miss more. Automated capsule inspection systems use cameras and image processing to check every unit and reject defects at full production speed — the kind of check that’s impossible to do reliably by hand past a few thousand capsules an hour.

If you’re planning a new capsule product or upgrading a line, it pays to think of the shell, the filler, and the downstream QC equipment as one system. A consultation with an equipment specialist before you buy usually costs nothing and saves the expensive kind of learning.

The bottom line

Pill capsules are made of gelatin or HPMC in almost every case, with pullulan and soft gelatin covering specific niches. Around that base material sits a small cast of supporting ingredients—water, colorants, and gelling agents—each with a job to do. The choice between materials comes down to your fill formula, your target markets, and how the shells behave on your equipment. When you get that match right, the capsule disappears into the background, which is exactly where it belongs.

FAQ

How long does a capsule take to dissolve in the stomach?

A standard gelatin capsule typically disintegrates in gastric fluid at body temperature within 10 to 20 minutes. HPMC capsules fall in a similar range, though the exact time depends on the shell grade and fill material. Enteric-coated capsules are a deliberate exception — they’re designed to survive the stomach and release in the intestine instead.

Are gelatin capsules halal, kosher, or vegetarian?

It depends on the source. Bovine gelatin from certified animals can be halal or kosher with the right documentation. Porcine gelatin is neither, and no gelatin capsule is vegetarian. If your product needs to serve all of these markets at once, HPMC shells are the simplest answer.

How should empty capsules be stored?

Keep them sealed in their original bags at 15–25°C and 35–65% relative humidity, away from direct light. Temperature swings and open bags are the two fastest ways to ruin a lot—gelatin shells either dry out and turn brittle or absorb moisture and go soft. Stored properly, quality shells keep for around five years.