Evaluation of a black widow spider bite begins with a history and physical examination. Without historical confirmation of a spider bite, this condition may be very difficult to detect.

Physical findings in someone with a black widow spider bite may include:

• Fang marks, redness and erect hair at the site of the bite
• High or low blood pressure
• Rapid heart rate
• Slow heart rate
• Severe muscle spasms
• Abdominal rigidity

There are no tests that help make the diagnosis of a black widow spider bite.