Types of Capsules: The Ultimate Beginner Guide (Hard vs Softgel, Gelatin vs HPMC, Enteric vs Controlled Release)

Capsules are a fundamental and highly versatile component of solid oral dosage forms across the pharmaceutical and nutraceutical sectors. They can efficiently mask the unpleasant taste or odor of active pharmaceutical ingredients (APIs) and support patient compliance—one reason capsules remain a global standard.

But capsule selection is not a cosmetic choice. The encapsulation technology you choose can influence product stability, bioavailability (the extent and rate of absorption), therapeutic efficacy, and—just as important—the feasibility and efficiency of the manufacturing process. This technical analysis breaks down the modern Types de capsules by structure, shell material, and functional release design, then connects those choices to the operational capabilities required of Capsule Filling Machine technology. For readers searching specifically for Types of Capsules in Pharmacy, the same engineering logic applies: the “right” capsule type is the one whose performance targets can be manufactured repeatably at scale.

Types of Capsules: Structure, Fill, and Encapsulation Machinery

Most decisions start with structure, because structure determines what the filling and sealing equipment must do. In industrial terms, capsules fall into two primary structural families: hard capsules (two-piece systems) et softgel capsules (monolithic, hermetic seals).

Hard capsules

Hard capsules consist of two separable, rigid cylindrical shells—the cap and the body—designed to interlock after filling. Historically, hard capsules are the primary container for dry, solid oral dosage forms, including powders, granules, pellets (multiparticulate systems), and micro-tablets. Modern technology has expanded the application space: certain two-piece shells can also be used for liquid-filled hard capsules when the fill is non-aqueous and the closure is validated.

The industrial advantage of hard capsules is versatility, but that versatility depends on how the Capsule Filling Machine handles separation, dosing, and closure with repeatable precision. High-throughput production requires tight control of shell handling, powder flow, pellet integrity, and closure force—otherwise defects show up as weight variability, deformed shells, or poor locking.

Capsule filling machine cycle (hard capsules)
A high-throughput capsule filler typically executes this sequence:

• Capsule orientation & feeding (minimizing chips and deformation)
• Separation (holding cap and body securely)
• Dosing (powder/pellet/liquid stations matched to material behavior)
• Closing & locking (controlled force for consistent lock integrity)
• Discharge (handoff to inspection and packaging)

Softgel capsules

Softgel capsules (soft gelatin capsules, or “liquid gels”) are single-unit, seamless, elastic shells—often oval or spherical—and hermetically sealed. Softgels are ideally suited for liquid, oil-based, emulsion, or semisolid fills. One technical reason softgels are frequently selected is their potential to enhance bioavailability for poorly soluble APIs by presenting actives in a pre-solubilized or dispersed state; a clinical study on melatonin reported improved bioavailability in soft gel capsules compared with powder formulations even at a reduced dose. (PubMed)

Softgel manufacturing is fundamentally different from hard capsule filling. Instead of separating and closing two rigid parts, softgel encapsulation machines form the shell, meter the fill, and seal in a single continuous process. Shell composition typically includes gelatin, water, and plasticizing agents (such as glycerin or sorbitol) to tune elasticity and hardness—parameters that directly affect seam integrity, leak risk, and drying behavior.

Table 1 — Capsule structure vs the machine capability it demands

Shell Materials: Gelatin vs HPMC and the Stability Window

Within the Types de capsules landscape, shell material drives chemical compatibility, moisture behavior, and market alignment. In practice, it also defines how narrow your storage and handling window must be to keep shells machinable.

Traditional gelatin capsules

Gelatin capsules are the long-established industry standard. Gelatin shells are animal-derived (collagen-based) and are commonly processed using acid (Type A) or alkali (Type B) methods. They also have a functional moisture range: when humidity is too low, shells can become brittle and crack under mechanical stress; when humidity is too high, shells can soften and deform.

A widely cited control window for hard gelatin capsules is 15–25°C et 35–65% relative humidity (RH), which helps keep capsule moisture in the workable range and reduces brittleness risk.
For moisture-sensitive APIs, the key point is not that gelatin is “bad,” but that gelatin shells require tighter environmental and packaging discipline to keep the shell and the fill stable over the full supply chain.

HPMC (vegetarian) capsules

Hydroxypropyl methylcellulose (HPMC) capsules are cellulose-derived and widely used for vegetarian, vegan, kosher, or halal positioning. Technically, HPMC capsules often have lower moisture contents and can show stronger humidity resilience than gelatin in certain applications.

It’s common to see HPMC handling expectations that tolerate a broader RHPMCrange than gelatin (often cited up to around 70% RHPMCunder typical storage assumptions), which is one reason HPMC is frequently considered for moisture-sensitive or hygroscopic fills.
That said, no shell is a substitute for good barrier packaging when the formulation is strongly hygroscopic or oxygen-sensitive—shell choice and packaging design must be treated as one system.

Table 2 — Gelatin vs HPMC capsules: practical technical differences

Functional Designs: Enteric, Sustained, and Controlled Release

A sophisticated category of Types de capsules treats the capsule not merely as a container, but as an engineered component controlling the drug’s release profile within the gastrointestinal tract.

Delayed-release (enteric-coated) capsules

Delayed-release formulations are designed to prevent immediate release in the stomach. The most common method is enteric coating: a polymer barrier applied to the capsule or its contents that remains intact in the highly acidic stomach environment and dissolves in the less acidic (or alkaline) environment of the small intestine. This design is used to protect acid-sensitive APIs from degradation and to mitigate gastric irritation for certain drug substances.

In practice, enteric performance is defined by two things: resistance in acid and reliable disintegration/dissolution after the pH transition. That requirement pulls the discussion back to manufacturing control—coating uniformity, shell–coating compatibility, and moisture conditioning all affect whether the “delayed” profile is consistent batch to batch.

Sustained and controlled-release capsules

Sustained-release and controlled-release capsules are engineered to release active ingredients over an extended period. A common design approach is to fill coated pellets (multiparticulate units) into a capsule shell; The pellet sizes in the 0.5–1.5 mm range (roughly 500–1500 microns).

The primary benefit of this multiparticulate approach is profile stability and flexibility. Different pellet populations can be blended to shape the final release curve, while the capsule serves as the convenient dose container. From an equipment standpoint, these products raise the precision bar. The fully automatic capsule machine must be equipped with pellet stations engineered to be gentle and highly repeatable. Uniform pellet dispersion and dosing consistency are essential because small deviations can shift the intended release profile.

Precision Drivers: Capsule Size, Bulk Density, and Equipment Capability

Industrial dosage precision depends on matching bulk formulation properties to capsule size and to the mechanical capabilities of the filling equipment. Standard hard capsule sizes are numerically coded from 000 (largest) down to 5 (smallest). Practical fill weight is not defined by volume alone; it depends on bulk density and particle size distribution. The powder fill weights vary widely across sizes and densities, and can reach into the gram range for larger capsules depending on the formulation’s bulk density.

Because density and flow behavior drive dosing variability, formulation and equipment are inseparable. A high-quality Capsule Filler Machine should be able to:

• cover the required capsule sizes with stable, repeatable changeover
• support dosing principles suited to the formulation (powder, pellet, or liquid)
• maintain closure consistency at industrial throughput
• integrate inspection and downstream packaging interfaces

Physical attributes also intersect with patient use and safety. FDA guidance highlights that differences in physical characteristics (including size and shape) may affect patient compliance and acceptability or could contribute to medication errors—reinforcing why capsule dimensions and appearance are not “just branding.”

CGMP and Process-Control Considerations

When capsule programs struggle at scale, the root cause is often loss of control over moisture, mechanical stress, or fill behavior—not the capsule type alone. Two principles consistently matter:

• Environmental control: holding temperature and RH within an agreed window for the selected shell material to preserve machinability.
• System alignment: ensuring shell, fill, dosing station, and primary packaging barrier are designed to work together—especially for hygroscopic APIs or oxygen-sensitive oils.

In a CGMP context, the goal is evidence-based repeatability: stable dosing performance, closure integrity, and release-profile verification (where modified release is used). That’s also why equipment evidence matters. For example, at Ruidapacking, outgoing capsule machines are commonly verified with a 24-hour continuous run plus an 8-hour high-load verification window before shipment—one practical way to show performance stability rather than relying on short demonstrations.

Conclusion

The most useful way to understand the Types de capsules is as an engineered system: structure defines the encapsulation route, shell material sets the stability behavior and market alignment, and functional designs (enteric, sustained, controlled-release) govern performance in the gastrointestinal tract. Across every category, therapeutic outcomes rely on industrial repeatability—so capsule technology ultimately ties back to precision equipment. If your product strategy requires multiple capsule formats (powder + pellets + liquids, or modified release alongside immediate release), make sure your fully automatic capsule machine capability is planned early, because it determines what is realistic to scale.

FAQ

1) What are the primary structural Types of Capsules?

Capsules are primarily categorized into hard capsules (two-piece systems) and softgel capsules (single-unit, hermetically sealed shells).

2) What are hard capsules typically used to encapsulate?

Hard capsules are traditionally used for powders, granules, pellets, and micro-tablets, and some technologies allow non-aqueous liquids in validated two-piece shells.

3) What are softgel capsules best suited for?

Softgels are best suited for oils, emulsions, suspensions, and semi-solid fills where a hermetic seal and protection against oxidation or volatility are important.

4) Why can softgels improve bioavailability for some APIs?

Softgels can present an API in a solubilized or dispersed form, which may improve absorption for poorly soluble compounds. Evidence exists for improved melatonin bioavailability in soft gel capsules.

5) What is the main difference between gelatin capsules and HPMC capsules?

Gelatin shells are animal-derived and sensitive to humidity excursions; HPMC shells are cellulose-derived, often lower in moisture, and can show broader humidity resilience in some applications.

6) What is an enteric coating?

An enteric coating is a polymer barrier that resists stomach acid and dissolves in the intestine, enabling delayed release.

7) Why do pellets matter in controlled-release capsules?

Pellets carry modified-release coatings; their integrity and dosing uniformity are essential to maintain the intended release profile.

8) How does capsule size affect manufacturing?

Capsule sizes run from 000 to 5, and practical fill weight depends heavily on bulk density and particle size distribution, which affects dosing repeatability.

Références

FDA: Size, Shape, and Other Physical Attributes of Generic Tablets and Capsules (Oct 2022). (Administration américaine des denrées alimentaires et des médicaments)

PubMed: Soft gel capsules improve melatonin’s bioavailability in humans (2014). (PubMed)