Is septicemia the same thing as "blood poisoning"?

No: Septicemia refers to the presence of infectious organisms(bacteria, fungi or viruses) in the blood stream and the occurrence of symptoms such as fever and low blood pressure. Blood poisoning is not a medical term per se. Blood poisoning could refer to almost anything including actual ingested poisons. Doctors don't use the term blood poisoning.

We can say: Septicemia- in lay man terms can be called blood poisoning. Some bacteria produce what are called endotoxins which circulate in the blood stream, cause serious illness.

Yes: The common term "blood poisoning" is the same thing as septicemia which means bacteria in the blood stream.