Acute Kidney Injury
Feeling Fine Does Not Replace the Repeat Blood Test
General information from an emergency physician. It adds to your discharge papers and does not replace them or your own doctor. What this site is and isn’t
Key Takeaways:
- Acute kidney injury is a sudden drop in how well the kidneys filter blood.
- About two-thirds resolve within 7 days, but future kidney risk can remain.
- Avoid NSAID pain relievers such as ibuprofen and naproxen, and get the repeat tests your follow-up provider orders.
About Your Diagnosis and ED Workup
Acute kidney injury, or AKI, means the kidneys suddenly filter less blood. It is found through a rise in creatinine, a waste product measured in blood, or through low urine output.
AKI often causes no pain or clear symptom. Urine amount can also be a poor clue. AKI is often found on a blood test done for another reason. A healthy person can lose nearly half of kidney filtering ability before creatinine leaves the normal range.
There are three broad causes. Too little blood may reach kidneys that are still structurally intact. Kidney tissue itself may be injured. Or urine flow may be blocked. Dehydration, bleeding, infection, heart failure, medicines, stones, and an enlarged prostate are among the causes.
The kidneys use blood pressure across tiny filters. NSAIDs can reduce blood entering that filter. ACE inhibitors and ARBs can reduce pressure at the other end. During dehydration or low blood flow, combining these effects can cause a steep drop in filtering.
First Steps and Evidence-Based Home Care
1. Avoid NSAID pain relievers
Avoid NSAIDs, including over-the-counter ibuprofen and naproxen. NSAIDs alone raise AKI risk about 3.5 times. Risk is much higher when they are combined with an ACE inhibitor or ARB and a diuretic.
2. Do not change prescription medicines on your own
Whether an ACE inhibitor, ARB, or diuretic should pause depends on how severe the AKI is and why it happened. Some medicines held during an acute illness may be resumed after the acute problem resolves, but that timing is an individual clinical decision. Ask the clinician who knows your medicine list.
3. Drink fluids as directed and review everything you take
Stay hydrated according to the plan you were given, and bring a complete medicine list to follow-up. Include over-the-counter medicines, vitamins, creatine, and herbal products. Some supplements can injure kidneys.
Timeline and Expected Recovery Course
About two-thirds of AKI resolves within 7 days. If low blood flow is corrected before cells are injured, filtering can recover quickly. Recovery after kidney-tube injury requires surviving cells to repair the tube and clear debris.
Recovery is not guaranteed. Some people recover only part of their former kidney function. Even mild or brief AKI can raise the future risk of chronic kidney disease. About one-quarter have another AKI within 12 months. A creatinine that returns to baseline does not remove the need for follow-up.
Emergency Red Flags: Return Immediately
Return to the emergency department if any of these happen:
- You make much less urine or cannot urinate.
- Your legs or face become more swollen.
- You keep vomiting or cannot keep fluids down.
- You become confused or extremely tired.
- You become short of breath.
- You see blood in the urine or the urine becomes newly foamy.
- You develop fever or other signs of infection.
This list does not cover everything. Return to the emergency department if you are worried about a serious change.
Reviewed September 3, 2026