- Bleeding: GI, GYN, GU, traumatic
- Poor oral intake
- Large insensible losses
- Leaking or fully ruptured arterial aneurysm (e.g. AAA, TAA)
- Lightheaded, dizzy, weak, confused, unconscious
- Provoked by standing, or present at baseline if volume loss severe
- May be ill appearing
- +orthostatic vital sign changes
- Periphery may feel cool/mottled, with delayed capillary refill