Dehydration occurs when your body does not have as much water and fluids as it should.
Dehydration can be mild, moderate, or severe, based on how much of your body's fluid is lost or not replaced. Severe dehydration is a life-threatening emergency.
You can become dehydrated if you lose too much fluid, do not drink enough water or fluids, or both.
Your body may lose a lot of fluid from:
You might not drink enough fluids because:
Older adults and people with certain diseases, such as diabetes, are also at higher risk for dehydration.
Signs of mild to moderate dehydration:
Signs of severe dehydration:
Your health care provider will look for these signs of dehydration:
Your doctor may do lab tests:
To treat dehydration:
Dehydration caused by a stomach virus should get better on its own after a few days.
If you notice signs of dehydration and treat it quickly, you should recover completely.
Untreated severe dehydration may cause:
You should call 911 if:
To prevent dehydration:
Kenefick RW, Cheuvront SN, O'Brien KK. Dehydration, rehydration, and hyperhydration. In: Auerbach PS. Wilderness Medicine. 6th ed. Philadelphia, PA: Elsevier Mosby; 2012:chap 70.
Padlipsky P. Infectious diarrheal disease and dehydration. In: Marx JA, Hockberger RS, Walls RM, et al, eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. 8th ed. Philadelphia, PA: Elsevier Mosby; 2014:chap 173.
Last reviewed on: 8/29/2015
Reviewed by: Laura J. Martin, MD, MPH, ABIM Board Certified in Internal Medicine and Hospice and Palliative Medicine, Atlanta, GA. Also reviewed by David Zieve, MD, MHA, Isla Ogilvie, PhD, and the A.D.A.M. Editorial team.