How long does alcohol stay in the blood?

Breath: Alcohol can be detected in your breath via a breathalyzer test for up to 24 hours.
Urine: Alcohol can be detected in urine for three to five days via ethyl gluconoride (EGT) metabolite or 10 to 12 hours via traditional method.
Blood: Alcohol can show up in a blood test up to 12 hours.
Saliva: A saliva test can be positive for alcohol from one to five days.
Hair: Like many other drugs, alcohol can be detected with a hair follicle drug test for up to 90 days.

The metabolism times above are estimated for the average person. There are other factors that can affect how quickly or slowly your body will eliminate alcohol from your system.

Some of those factors include:

Genetic sex
Ethnicity
Body fat content
Age
How much you had to eat before drinking or while drinking
Fat content of the food you ate
Medications
How fast you consumed the alcohol

Sources:

Alcohol Metabolism: An Update. National Institute on Alcohol Abuse and Alcoholism.

Cederbaum AI. Alcohol Metabolism. Clinics in Liver Disease.

Drugs of Abuse Reference Guide. LabCorp, Inc.

Ethanol. American Association for Clinical Chemistry.