For infusion the certification you want is the CRNI - Certified Registered Nurse Infusion. This is given by the Infusion Nurses Certification Corporation (INCC). This is quite a difficult exam, so plan to study hard in preparation. Remember that certification is not simply a measure of your current knowledge base. It is an opportunity to expand your knowledge base and establish yourself as someone who has expertise in the subject matter.
If your plan is to go into vascular access as your specialty, the key exam there is the VA-BC, Vascular Access Board Certified. This is administered by the Vascular Access Certification Corporation (VACC), and is for SMEs in multiple disciplines who are highly knowledgeable in vascular access.
Getting certified is a very smart move for your career and your patients’ safety. Best of luck!