Inclusion Criteria:

• Clinical diagnosis, based on investigator assessment, of type 1 diabetes for at least one year and using insulin for at least 1 year. 
• Familiarity and use of a carbohydrate ratio for meal boluses. 
• Age ≥ 14.0 years old. 
• For females, not currently known to be pregnant. If female and sexually active, must agree to use a form of contraception to prevent pregnancy while a participant in the study. A negative serum or urine pregnancy test will be required for all females of child-bearing potential. Participants who become pregnant will be discontinued from the study. Also, participants who during the study develop and express the intention to become pregnant within the timespan of the study will be discontinued. 
• For participants <18 years old, living with one or more parent/legal guardian knowledgeable about emergency procedures for severe hypoglycemia and able to contact the participant in case of an emergency. 
• Willingness to suspend use of any personal CGM for the duration of the clinical trial once the study CGM is in use. 
• Investigator has confidence that the participant can successfully operate all study devices and is capable of adhering to the protocol. 
• Willingness to switch to lispro (Humalog) or aspart (Novolog) if not using already, and to use no other insulin besides lispro (Humalog) or aspart (Novolog) during the study. 
• Total daily insulin dose (TDD) at least 10 U/day. 
• Willingness not to start any new non-insulin glucose-lowering agent during the course of the trial.

Exclusion Criteria:

• Concurrent use of any non-insulin glucose-lowering agent other than metformin (including GLP-1 agonists, Symlin, DPP-4 inhibitors, SGLT-2 inhibitors, sulfonylureas). 
• Hemophilia or any other bleeding disorder. 
• A condition, which in the opinion of the investigator or designee, would put the participant or study at risk. 
• Participation in another pharmaceutical or device trial at the time of enrollment or during the study. 
• Employed by, or having immediate family members employed by Tandem Diabetes Care, Inc. or TypeZero Technologies, LLC, or having a direct supervisor at place of employment who is also directly involved in conducting the clinical trial (as a study investigator, coordinator, etc.); or having a first-degree relative who is directly involved in conducting the clinical trial.