Capsules are one of the most widely used dosage forms for pharmaceuticals, vitamins, and dietary supplements. They may look simple, but choosing the wrong capsule can lead to a chain of problems—difficult filling, powder leakage, poor dissolution in the body, or even regulatory rejection that prevents a product from entering the market.

For manufacturers, a capsule is not just an outer shell. It is a critical part of the formulation and the entire production system.

This guide will help you clearly understand common capsule materials, major capsule types, sourcing channels, and—most importantly—how to select the right capsule based on your formulation characteristics, production conditions, and target market.

What Is a Capsule?

A capsule is a hollow shell designed to hold drugs or active ingredients. After ingestion, it dissolves in the body and releases the contents.

Capsules are widely used because they are easy to swallow, provide accurate dosing, and can contain powders, granules, liquids, or oils.

What Are Capsules Made Of?

Currently, capsule materials mainly fall into three categories.

1. Gelatin Capsules

Gelatin capsules are derived from animal sources. They offer excellent elasticity, are easy to manufacture, and dissolve quickly in the body. They are the most commonly used capsules in both pharmaceutical and dietary supplement industries.

2. Vegetarian (Plant-Based) Capsules

Vegetarian capsules are typically made from plant cellulose, such as HPMC. They contain no animal-derived ingredients and are suitable for vegetarian products. They also perform better in high-humidity environments and are more compatible with moisture-sensitive formulations.

3. Functional Capsules

Functional capsules include enteric-coated capsules and modified-release capsules. They are designed to release contents in specific areas of the gastrointestinal tract and are used when protection from stomach acid or targeted release is required.

Capsules can also be clear or colored. Clear capsules allow visual inspection of the contents, while colored capsules are often used for branding and product differentiation.

How to Choose Capsules Based on the Filling Material

How to Choose Capsules Based on Production Conditions

• High-speed filling lines usually favor gelatin capsules due to their superior elasticity and locking performance.
• In high-humidity environments, vegetarian capsules are more stable and less prone to deformation.
• For large-scale mass production, gelatin capsules offer cost advantages and higher filling efficiency.
• For R&D or small-batch production, either gelatin or vegetarian capsules can be used, depending on future scale-up plans.

Common Capsule Types

• Hard capsules consist of two parts (cap and body) and are the most common type, mainly used for powders and granules.
• Soft capsules, also known as softgels, have a one-piece structure with excellent sealing performance and are primarily used for oils and liquid formulations.
• Functional capsules, such as enteric-coated or sustained-release capsules, are designed to meet specific release requirements.

How Are Capsules Filled?

• For laboratory testing or pilot trials, manual capsule filling machines are commonly used.
• For small to medium batch production, semi-automatic capsule filling machines provide better efficiency and consistency.
• For large-scale manufacturing, fully automatic capsule filling lines are required to ensure high output and stable quality.

Where to Buy Empty Capsules?

• Empty capsules should be sourced from qualified suppliers that comply with GMP standards and hold pharmacopeia certifications such as USP or EP.
• Manufacturers should clearly distinguish between pharmaceutical-grade and food-grade capsules and pay close attention to batch-to-batch consistency and long-term supply stability.

Capsule Size Selection in Real Production

Capsule sizes are standardized and range from size 000 (largest) to size 5 (smallest).

Selecting the correct size depends on both the dosage and the bulk density of the filling material. For example, a 500 mg herbal powder typically requires a size 0 or 00 capsule, while a 100 mg API may fit into a size 3 or 4 capsule.

Oversized capsules can be difficult for consumers to swallow, while undersized capsules may cause poor fill accuracy and production issues.

A Simple Capsule Selection Logic

Standard dry powders with strong cost sensitivity are best matched with gelatin capsules.

Moisture-sensitive formulations or products targeting vegetarian markets are better suited to vegetarian capsules.

Liquids or oils require softgels or liquid-filled hard capsules.

High-speed production lines should prioritize capsules with good mechanical compatibility and consistent quality.

Summary

Choosing the right capsule requires a comprehensive evaluation of formulation properties, production processes, equipment compatibility, and market positioning. The right choice can significantly improve production efficiency, product stability, and regulatory compliance.

If you are planning a capsule-based product or upgrading your filling line, please feel free to contact us.