What kind of red meat did you eat?
How long after eating did you feel ill?
When you say you can't walk standing up - is that because you are weak or dizzy?
Be sure to keep yourself hydrated - drink plenty of fluids!
If I were you I would wait a full 48 hours and sort of "weather the storm" to see if it subsides. Then on the 3rd day if I would seek medical attention.
Just be sure to stay hydrated!
You may want to follow a BRAT diet:
The BRAT diet is a treatment sometimes used when a young child who eats solids has diarrhea. BRAT is an abbreviation of bananas, rice, apple sauce and toast. This diet is also helpful for any child that has fever, flu, cold, or general illness with a loss of appetite. The BRAT Diet may also be recommended for adolesent and adult patients who present with symptoms of dyspepsia or gastroenteritis. This BRAT diet also has several minor "spin-offs" such as the BRATT (Bananas, Rice, Apple Sauce, Toast and Tea) or the BRATY (Bananas, Rice, Apple Sauce, Toast, and Yogurt) depending on the severity of symptoms. The BRAT diet is designed to be easy on the stomach and intestines which may be inflamed due to trauma or illness.