Is spirulina negatively interacting with warfarin? thank you

Yes: Spirulina has high vitamin k content, which will increase your INR while on warfarin. You can still take it as a supplement, but the important thing is to be consistent - keep doing what you've been doing and you'll be fine.

Interactions: You can use an interaction checker when you have questions about drug interactions with herbal or natural medications. Here is one example: http://naturaldatabase.therapeuticresearch.com/nd/search.aspx?s=nd&pt=7