The empty capsules market hit $2.8 billion in 2024. Analysts expect it to grow at 7.2% annually through 2032. Capsules are the second most prescribed oral solid dosage form after tablets. Formulators pick them because they hide bad tastes, shield sensitive ingredients from moisture and oxygen, and deliver accurate doses in something easy to swallow. Between clean-label pressure, the vegetarian market, and nutraceutical innovation, manufacturers now have more capsule choices than they did ten years ago.
There are five main types of capsules in pharmaceutical and nutraceutical manufacturing: hard gelatin capsules, soft gelatin capsules, HPMC vegetarian capsules, pullulan capsules, and liquid-filled hard capsules. Each one has a different shell material, manufacturing process, fill compatibility, dissolution profile, and target consumer. The main factors are the active ingredient’s chemical stability, how quickly it needs to release, and whether your market prefers animal or plant-based products.
Here is what each type does, how it is made, and what equipment you need to produce and inspect it at scale.
What Are the Main Types of Capsules?
Capsules fall into two structural groups: two-piece hard capsules and one-piece soft capsules. They also separate into four shell material groups: gelatin (animal), HPMC (plant cellulose), pullulan (fermented starch), and gelatin or HPMC shells with liquid fill. Modern manufacturing runs all of these formats with capsule filler machines and the right downstream equipment.
Two structural formats
Hard capsules have a body and a shorter cap that fit together. The shells are made empty, then filled with powder, granules, pellets, or sometimes liquid or semi-solid fills. Soft capsules are formed, filled, and sealed in a single continuous step. They usually hold liquid or suspension formulations.
Shell material differences
The shell material sets the capsule’s oxygen permeability, moisture content, dissolution behavior, and whether vegetarian, halal, or kosher consumers will accept it. A production line built for hard gelatin capsules does not directly transfer to softgel manufacturing. The tooling is different, the process controls are different, and the capital cost is different.
Hard gelatin capsules: the industry standard
Hard gelatin capsules are the most common type in pharma, making up about 60% of all capsule products. They are two-piece shells made from Type A or Type B gelatin (animal collagen, usually bovine or porcine). The body and cap telescope together after filling.
Why gelatin dominates
Gelatin dissolves fast in stomach fluid: five to ten minutes at body temperature. That makes it a good match for immediate-release drugs. The film strength is high when moisture stays between 13% and 16%. Having a century of manufacturing experience behind it does not hurt either: the process is mature, the equipment is everywhere, and regulators know what to expect.
Filling formats and speeds
Hard gelatin capsules take powder blends, granules, beads, pellets, and micro-tablets. The filling happens through tamping pins, dosator nozzles, or vacuum-assisted dosing on automatic machines. These lines process both gelatin and plant-based empty capsules. Speeds range from 6,000 to 200,000 capsules per hour depending on the machine tier.
The moisture problem
Gelatin shells get brittle below 10% moisture and sticky above 18%. Storage needs climate control. Hygroscopic formulations that pull water out of the shell do not work well in hard gelatin. Neither do liquid fills, which would dissolve the shell. For those, you go to softgels or liquid-filled hard capsules.
Soft gelatin capsules: liquid-filled solutions
Soft gelatin capsules (softgels) are one-piece sealed shells formed, filled, and cut in a single rotary-die process. The shell contains a plasticizer (glycerol, sorbitol, or propylene glycol) that gives it flexibility. Softgels work especially well for liquid, oil-based, and suspension fills.
Bioavailability is the real selling point
Many APIs are poorly water-soluble, with low and unpredictable oral bioavailability. Put those compounds in a lipid vehicle inside a softgel, and absorption can double compared to a standard tablet. Isotretinoin, cyclosporine, and ibuprofen all ship in softgel form because of this.
How rotary die encapsulation works
Two gelatin ribbons feed between rotating dies. Liquid fill injects between the ribbons, and the dies seal and cut each capsule in one motion. A full softgel line combines gel mass prep, ribbon formation, fill injection, die cutting, and initial drying in a cleanroom environment. It is a lot of moving parts in one machine.
Why consumers like them
Softgels are smooth and easy to swallow. Their opaque shell masks odors and tastes better than most tablet coatings. The visual range (colors, finishes, shapes) matters for brands selling direct to consumers. It is not pure function: people judge supplements by how they look.
HPMC (Vegetarian) Capsules: Plant-Based Alternatives
HPMC capsules use hydroxypropyl methylcellulose from plant cellulose. They have no animal ingredients, which means they pass vegetarian, vegan, halal, and kosher checks out of the box. Market share has gone from under 5% a decade ago to nearly 20%.
Moisture and cross-linking advantages
HPMC runs at 3% to 7% moisture, compared to 13% to 16% for gelatin. That makes it a much better fit for moisture-sensitive and hygroscopic formulations. It does not cross-link with aldehydes or reducing sugars the way gelatin does. Cross-linking is a real stability headache: it slows dissolution over shelf life. HPMC capsules also dissolve independent of pH, which matters if you are targeting a specific gut region.
Cost and production reality
Historically, HPMC had two problems: slower dissolution and higher cost. The dissolution gap has mostly closed. Newer formulations add carrageenan and potassium chloride as dissolution promoters, and the results match gelatin in most cases. The price gap has narrowed as volumes have scaled. For new drug development, HPMC is often the default capsule choice for global regulatory filings.
Equipment compatibility
HPMC runs on the same capsule filler machines as gelatin. The adjustments needed for the two are small: maybe just a change in the dosing disc or a humidity tweak in the filling room. HPMC is more static-prone, so humidity control matters more. But the capital investment largely overlaps.
Pullulan Capsules: The Premium Natural Option
Pullulan capsules use a polysaccharide fermented from tapioca starch. Their oxygen permeability is the lowest of any shell material: about 1% of gelatin and 10% of HPMC. That makes them the natural choice for oxygen-sensitive APIs, probiotics, and premium nutraceuticals where oxidation kills shelf life.
The oxygen barrier advantage
The fermentation process uses the fungus Aureobasidium pullulans to produce a linear alpha-glucan. The film is clear, glossy, and preservative-free. These capsules are non-GMO, gluten-free, and plant-based, so they overlap with HPMC’s consumer segment. The difference is the oxygen barrier. HPMC cannot match it without adding specialized coatings.
When the higher cost makes sense
Pullulan costs more per unit than gelatin or HPMC. In high-margin nutraceuticals, the math often works out. A probiotic or CoQ10 in a pullulan capsule can claim a longer shelf life without loading antioxidant overages into the formula. That matters on a retail shelf where “clean label” and “no artificial preservatives” are printed on the front of the bottle. In pharmaceuticals, pullulan is still niche but growing for oxygen-sensitive molecules in clinical programs.
Liquid-filled hard capsules: a hybrid approach
Liquid-filled hard capsules (LFHC) put a liquid or semi-solid fill inside a hard gelatin or HPMC two-piece shell. The setup lets you get liquid delivery’s bioavailability boost on standard hard capsule filling lines without buying softgel rotary die equipment.
How LFHC works
You fill a liquid or thixotropic formulation into the open body of a hard capsule, then seal the cap-body joint with banding or micro-spray. The seal stops leaks. This approach works for low-dose potent compounds that benefit from solution delivery and for early clinical supplies where softgel tooling is not yet justified.
Why CDMOs like it
CDMOs have picked up LFHC because it lets them run liquid fills on existing capsule filling lines. Modified machines with liquid dosing pumps alongside powder dosing stations can switch between solid and liquid filling in the same production cycle. That flexibility means fewer idle machines and faster turnaround for clients with different fill formats.
How to Choose the Right Capsule Type
The decision depends on API chemistry, target patient or consumer, manufacturing scale, and cost. Below is how the five types stack up.
| Criterion | Hard Gelatin | Softgel | HPMC | Pullulan | LFHC |
|---|
| Shell material | Animal gelatin | Gelatin + plasticizer | Plant cellulose | Fermented starch | Gelatin or HPMC |
| Fill type | Powder, pellets, granules | Liquid, oil, suspension | Powder, pellets | Powder, pellets | Liquid, semi-solid |
| Oxygen barrier | Moderate | Good | Moderate | Excellent | Varies |
| Moisture content | 13-16% | 6-10% | 3-7% | 8-12% | Varies by shell |
| Vegetarian suitable | No | No | Yes | Yes | Can be (HPMC) |
| Typical cost per 1000 | Low | Medium | Medium | High | Medium-High |
| Bioavailability boost | Standard | High (lipid) | Standard | Standard | High (liquid) |
Downstream equipment matters too
The capsule type affects more than the chemistry. Capsules that go through a tablet press for combination products, or through tablet coating machines for functional coatings, have to survive mechanical stress without cracking. Inspection equipment, whether for capsules or tablets, needs calibration for each capsule type’s optical properties and common defect patterns. A machine set up for opaque gelatin shells will not correctly inspect clear HPMC capsules without reconfiguration.
Capsule Manufacturing and Quality Control Equipment
A full capsule line is more than a filling machine. The standard flow is filling, polishing, inspection, counting, and packaging. At an industrial scale, how well these stations integrate determines your overall line speed.
Filling machines
Capsule-filling machines separate empty capsules, dose the fill, rejoin the cap and body, and eject the finished product. Semi-automatic models work for low volume. Above about 50,000 capsules per day, you need an automatic machine. The difference in throughput between a manual line and a 200,000-per-hour automatic filler changes your entire production economics.
Inspection and polishing
Capsule inspection systems use high-speed cameras and machine vision to catch cracks, dents, bad joins, and foreign particles. After inspection, capsule polishing machines remove surface dust and fill residue. If you skip polishing, the dust will eventually jam your packaging equipment. These systems run at 30,000 to 100,000 capsules per hour and reject bad units automatically.
Shared QC for mixed facilities
Manufacturers running both capsules and tablets can share checkweighers and metal detectors across lines. Tablet-specific stations like dedusters and coating pans only serve one form factor. If you produce both, your floor plan has to account for the extra footprint. Counting and packaging are where things converge: capsule-counting machines and tablet-pill counters fill bottles or blister packs with photoelectric verification. Shared packaging lines with format changeover are common in mixed facilities.
Conclusion
Hard gelatin, soft gelatin, HPMC, pullulan, and liquid-filled hard capsules each serve distinct formulation needs. Hard gelatin is still the workhorse for powder and pellet products. Softgels own the liquid and oil-based space where bioavailability is the priority. HPMC and pullulan address vegetarian, clean-label, and oxygen-protection demands. LFHC bridges solid and liquid filling on one production line.
For manufacturers, the capsule type you pick determines not just product performance and consumer perception, but also every piece of equipment from filling through packaging. A capsule filler set up for size 0 gelatin requires only minor changes for size 0 HPMC. Moving from hard capsules to softgels means an entirely different production line with different capital, different floor space, and different operator training.
Frequently Asked Questions
What is the difference between capsules and tablets?
Capsules put the active ingredient inside a dissolvable shell. Tablets are compressed powder, sometimes coated for controlled release. Capsules dissolve faster in most cases and hide bitter tastes better than uncoated tablets. The tradeoff is cost: capsules cost more per dose to make. The decision usually depends on the API’s compressibility, the release profile you need, and whether patients will actually swallow the thing.
How long does it take for a capsule to dissolve in the stomach?
Gelatin capsules: 5 to 10 minutes in gastric fluid at body temperature. HPMC: 10 to 20 minutes, though formulations with dissolution promoters can hit gelatin timing. Pullulan falls between the two. Softgels take a bit longer because of their thicker shell and glycerol content but still dissolve within 30 minutes. These numbers assume a fed stomach. Dissolution in a fasted state is faster across the board.
Can capsule filling machines handle multiple capsule sizes?
Most modern automatic filling machines have quick-change parts for sizes 000 (largest) through 4 or 5 (smallest). You swap the dosing disc, tamping pins, and capsule orientation segments. Changeover takes 30 to 90 minutes depending on the machine and who is doing it. This matters for contract manufacturers running multiple client products with different capsule specs on the same line.
