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: He needed dialysis for 2 weeks and was treated successfully with steroids for 6 months .
### Output Text:
He needed dialysis for 2 weeks and was treated successfully with <span class="chemical">steroids</span> for 6 months . 