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General information for lab and clinic staff, not medical advice. Anyone with these symptoms should contact a clinician.
Short answer
Fluid overload (hypervolemia) means having too much water in the body. The National Kidney Foundation lists swelling in the feet, ankles, wrist and face as a sign, along with cramping, headache, abdominal bloating, high blood pressure and shortness of breath. Clinical teams also measure it, using weight change and fluid intake against output.
Definition and scope
The National Kidney Foundation (NKF) defines fluid overload, also called hypervolemia, as having too much water in your body. Its patient page is written for people on dialysis, whose kidneys can no longer keep the body’s fluid balance right. Overload is not limited to kidney disease: a veterinary review of the topic in Frontiers in Veterinary Science (Hansen, 2021; dogs and cats, so animal evidence) describes hypervolemia as excessive blood volume with raised mean circulatory filling pressure, and lists impaired excretion from heart, kidney or liver disease among the causes.
This page covers recognition and measurement as general information. It gives no treatment, fluid-limit or dosing guidance. For what saline fluids are, see What Is 0.9% Sodium Chloride?
How it is recognised and measured in practice
What patients and carers notice
NKF describes swelling in the feet, ankles, wrist and face; cramping, headache and abdominal bloating; high blood pressure; and shortness of breath when extra fluid enters the lungs. It also notes effects on the heart, including heart rate and heart muscle, and a possible increase in heart size.
What clinical teams quantify
A chapter on managing fluid overload in the paediatric intensive care unit (Ker and Gangadharan, Pediatric Critical Care, Springer, 2018, via PubMed Central) uses a percentage. Following Goldstein (2001), percent fluid overload is cumulative fluid in minus fluid out, divided by weight at ICU admission, times 100. A weight-based alternative compares weight at the start of continuous renal replacement therapy with admission weight, and the authors state that daily weights can be substituted when intake and output records are incomplete. The chapter’s examples of findings include anasarca (generalised swelling), pulmonary edema on chest radiograph, weight above baseline and raised central venous pressure.
Types and related concepts: where the fluid goes
The veterinary review explains that raised circulatory pressure pushes fluid out of capillaries into surrounding tissue, so edema is suspected from pulmonary edema, peripheral edema or body cavity effusion,. The table sets each location beside what the cited sources report for it.
| Where fluid collects | What is reported | Source |
|---|---|---|
| Peripheral tissues | Swelling of feet, ankles, wrist and face; generalised swelling (anasarca) | NKF; Ker and Gangadharan |
| Lungs | Shortness of breath; pulmonary edema on chest radiograph | NKF; Ker and Gangadharan |
| Body cavities | Effusion, listed as a sign of edema (dogs and cats) | Hansen 2021 |
Where it matters for labs, clinics and supply decisions
Both the paediatric chapter and the veterinary review treat fluid given by clinicians as a contributor to overload, not only disease. Ker and Gangadharan say aggressive early fluid resuscitation can contribute to fluid overload in critical illness, and list excessive fluid and blood products as an intraoperative risk factor. Hansen names excess hypotonic maintenance fluids, sodium-rich fluids in excess volume and “fluid creep” from the volume of drug vehicles.
The cited literature tracks these items:
- Cumulative intake against output (Ker and Gangadharan).
- Daily weights, especially when intake and output records are incomplete (Ker and Gangadharan).
- Fluid carried by drugs and flushes, not only bags of fluid (Hansen, “fluid creep”).
- Blood pressure and breathing changes (NKF).
Equipment pages that touch this topic include What Is an IV Bag?, What Is an IV Infusion Pump?, What Is a Dialysis Machine? and What Is a Blood Pressure Cuff?
Common misunderstandings
- Swelling is the only sign. NKF lists breathlessness, headache, bloating and high blood pressure as well,.
- Weight is just a number. In the paediatric chapter, weight change is a formal way to quantify overload.
- It only affects people with kidney disease. Heart and liver disease and the volume of fluids given are also named as causes.
FAQ
What are the signs of fluid overload?
NKF names swelling in the feet, ankles, wrist and face, cramping, headache, abdominal bloating, high blood pressure and shortness of breath.
Is fluid overload the same as hypervolemia?
Yes. NKF says having too much water in your body is called fluid overload or hypervolemia.
Can IV fluids cause fluid overload?
The sources say fluid given by clinicians can contribute: aggressive early resuscitation in critical illness, excess hypotonic or sodium-rich fluids, and drug vehicle volumes. Decisions about any patient belong to their clinician.
How do clinicians measure it?
One published approach divides cumulative fluid in minus out by admission weight and multiplies by 100, with daily weights as a substitute when records are incomplete.
Sources
- National Kidney Foundation, Fluid Overload in a Dialysis Patient, checked 2026-10-30.
- Ker G, Gangadharan S. Management of Fluid Overload in the Pediatric ICU. Pediatric Critical Care, Springer, 2018. PMC7122561, checked 2026-10-30.
- Hansen B. Fluid Overload. Front Vet Sci 2021;8:668688 (veterinary). PMC8275824, checked 2026-10-30.
