This feasibility study is a prospective, single center, multi-arm study evaluating possible enhancements to the SteadiSet extended wear infusion set.

All participants will use the SteadiSet insulin infusion set for 6 wear periods of up to 7 days each.

The 2 treatment arms are:

Existing t:slim X2 Users:

• t:slim X2 insulin pump with SteadiSet (43 inches) and an enhanced filling process (3 wear periods)
• t:slim X2 insulin pump with SteadiSet (43 inches) with no side ports (3 wear periods)

Existing Mobi Users:

• Mobi Insulin Pump with SteadiSet (5 inches) and an enhanced filling process (3 wear periods)
• Mobi Insulin Pump and SteadiSet (5 inches) (3 wear periods)

Inclusion Criteria:

• Age 18 to 80 years old inclusive

• Generally in good health, as determined by the investigator

• Living in the United States with no plans to move outside the United States during the study

• Diagnosis of T1D for at least 12 months

• Currently using a Tandem pump

• Current Dexcom CGM user

• HbA1c <9.0% in the last 6 months.

• Willing to implement and adhere to pump alert/alarm settings on a study-provided pump as instructed during the study

• Willing to wear each investigational infusion set for up to 7 days during each of the wear periods in the study

• Willing to perform blood ketone and blood glucose (fingerstick) measurements as directed using provided ketone and blood glucose meters and strips

• If using Tandem Mobi, has a compatible cellular phone that can run the Tandem Mobi Mobile App

• BMI in the range 18-35 kg/m2, both inclusive

• Currently using one of the following insulins with no expectation of a need to change insulin type during the study:

  1. Humalog™ (or generic insulin lispro)
  2. NovoLog™ (or generic insulin aspart)

• Willing to change insulin cartridge every 48-72 hours, as recommended by patient's healthcare provider during the study

• Has the ability to understand and comply with protocol procedures and to provide informed consent

Exclusion Criteria:

• Concurrent use of any non-insulin glucose-lowering agent, other than metformin (for example, GLP-1 agonists, Symlin, DPP-4 inhibitors, SGLT-2 inhibitors, sulfonylureas)

• Female subject is pregnant, planning to become pregnant, or not using adequate method of contraception

• Episodes of severe hypoglycemia in the last 6 months resulting in:

  1. Medical Assistance (i.e., paramedics, hospital evaluation or hospitalization)
  2. Loss of consciousness
  3. Seizures

• One or more episodes of diabetic ketoacidosis (DKA) in the last 6 months requiring hospitalization

• Currently on a ketogenic or low-carbohydrate diet of less than 60 grams of carbohydrates per day, or intending to begin one during the study period

• Known history of any of the following conditions:

  1. Cushing's Disease
  2. Adrenal insufficiency
  3. Pancreatic islet cell tumor
  4. Insulinoma
  5. Lipodystrophy
  6. Extensive lipohypertrophy, as assessed by the investigator

• Undergoing treatment with systemic oral or intravenous corticosteroids, at or within the last 8 weeks from screening. Inhaled glucocorticoids are allowed.

• Significant history of any of the following, that in the opinion of the investigator would compromise safety or successful study participation:

  1. Alcoholism
  2. Drug abuse

• Significant acute or chronic illness, that in the opinion of the investigator might interfere with safety or integrity of study results

• Current participation in another clinical drug or device study

• Immediate family member (spouse, biological or legal guardian, child, sibling, parent) who is a study site personnel directly affiliated with this study or who is an employee of Tandem Diabetes Care