You can travel with blood in carry-on and in checked baggages. You must have a document which guarantees that it is free of infectious substances, and it must be packaged in Dry ice and comply with other requirements for transport.
When making your reservation or 48 hours before your flight, you must notify that you will be travelling with blood in your baggage.
For additional information, Not allowed or restricted items section for a complete list of what is/is not allowed in carry-on and/or checked baggage.