A medical system (100, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500, 1600) for anchoring an intravenous cannula device (105, 405, 505, 605, 705, 805, 905, 1005, 1105, 1205, 1305, 1405, 1505, 1605) in a subcutaneous region along an underside of a skin layer, comprising: an intravenous cannula device (105, 405, 505, 605, 705, 805, 905, 1005, 1105, 1205, 1305, 1405, 1505, 1605) including a flexible catheter (120, 420, 520, 620, 720, 820, 920, 1020, 1120, 1220, 1320, 1420, 1520, 1620), a proximal connector hub (115, 415, 515, 615, 715, 815, 915, 1015, 1115, 1215, 1315, 1415, 1515, 1615), and a subcutaneous anchor (130, 430, 530, 630, 730, 830, 930, 1030, 1130, 1230, 1330, 1430, 1530, 1630) integrally formed as a unitary structure with an outer wall of the flexible catheter, the flexible catheter including a lumen and extending distally of the proximal connector hub, and the proximal connector hub including a thread pattern configured to releasably connect with an external fluid line; and an inserter tool (110, 410) removably coupleable to the intravenous cannula device so as to insert the flexible catheter of the intravenous cannula device through a skin penetration point and into a targeted vessel, the inserter tool including a handle and an insertion needle extending distally from the handle, the insertion needle being slidably engageable with the lumen of the flexible catheter of the intravenous cannula device, wherein the inserter tool is removable from the intravenous cannula device when the insertion needle is proximally withdrawn from the lumen of the flexible catheter, wherein the subcutaneous anchor (130, 430, 530, 630, 730, 830, 930, 1030, 1130, 1230, 1330, 1430, 1530, 1630) is positioned between a distal tip of the flexible catheter and the proximal connector hub, and wherein the subcutaneous anchor includes at least one surface to engage tissue in the subcutaneous region along the underside of the skin layer when the flexible catheter of the intravenous cannula device is inserted through the skin penetration point and into the targeted vessel, wherein the subcutaneous anchor comprises one or more flexible circumferential rings (430, 530) integrally formed as a unitary structure with the outer wall of the flexible catheter. an intravenous cannula device (105, 405, 505, 605, 705, 805, 905, 1005, 1105, 1205, 1305, 1405, 1505, 1605) including a flexible catheter (120, 420, 520, 620, 720, 820, 920, 1020, 1120, 1220, 1320, 1420, 1520, 1620), a proximal connector hub (115, 415, 515, 615, 715, 815, 915, 1015, 1115, 1215, 1315, 1415, 1515, 1615), and a subcutaneous anchor (130, 430, 530, 630, 730, 830, 930, 1030, 1130, 1230, 1330, 1430, 1530, 1630) integrally formed as a unitary structure with an outer wall of the flexible catheter, the flexible catheter including a lumen and extending distally of the proximal connector hub, and the proximal connector hub including a thread pattern configured to releasably connect with an external fluid line; and an inserter tool (110, 410) removably coupleable to the intravenous cannula device so as to insert the flexible catheter of the intravenous cannula device through a skin penetration point and into a targeted vessel, the inserter tool including a handle and an insertion needle extending distally from the handle, the insertion needle being slidably engageable with the lumen of the flexible catheter of the intravenous cannula device, wherein the inserter tool is removable from the intravenous cannula device when the insertion needle is proximally withdrawn from the lumen of the flexible catheter, wherein the subcutaneous anchor (130, 430, 530, 630, 730, 830, 930, 1030, 1130, 1230, 1330, 1430, 1530, 1630) is positioned between a distal tip of the flexible catheter and the proximal connector hub, and wherein the subcutaneous anchor includes at least one surface to engage tissue in the subcutaneous region along the underside of the skin layer when the flexible catheter of the intravenous cannula device is inserted through the skin penetration point and into the targeted vessel, wherein the subcutaneous anchor comprises one or more flexible circumferential rings (430, 530) integrally formed as a unitary structure with the outer wall of the flexible catheter.