The present invention belongs to the pharmaceutical field and relates to a hard oral-administration capsule having acid-resistance properties and composed of a main cellulose or gelatin polymer, dispersants and plasticisers, and of a minimum proportion of a mixture of gelling agents, suitable for carrying pharmaceutical, veterinary, nutraceutical and dietary supplementation products. The main polymer is selected from the group of celluloses, preferably hypromellose, carboxymethyl cellulose, or from the group of gelatins, preferably from fleshings, while the mixture of gelling agents can include gums such as gellan gum, guar gum, tragacanth, carrageenans, agar, alginate and pepsin gum, preferably a combination of gellan gum and kappa carrageenan. The capsule can additionally contain colouring agents, sweeteners and flavouring agents. In the preferred embodiment, the hard capsule is based on 80% to 95% of a cellulose polymer such as hypromellose, 0.05% to 2% dispersant, 1% to 5% plasticiser and 0.04% to 3.5% of a mixture of gelling agents.