In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: Vegetarians may also take creatine to replace what they are not consuming from meat , fish , and other animal products .
### Output Text:
Vegetarians may also take <span class="chemical">creatine</span> to replace what they are not consuming from meat , fish , and other animal products . 