The same 200 mg as its category
Vivarin carries 200 mg of caffeine per tablet, by its drug label. That matches NoDoz Maximum Strength and a generic caffeine tablet exactly, so the choice between them is packaging and price rather than dose. One tablet carries roughly the caffeine of two and a half standard 8.4 oz cans of Red Bull, or about two 8 oz cups of drip coffee at USDA’s reference strength (95 mg each), delivered in one swallow instead of a cup you drink over several minutes.
At 200 mg, a single Vivarin tablet sits right at the 200 mg EFSA assessed as a safe single dose for healthy adults, and two tablets reach the full 400 mg the FDA cites as the daily figure for healthy adults, with nothing else counted.
Worth checking against other medicine
Caffeine tablets are easy to overlook as a medicine interaction because they’re sold near cold and allergy remedies rather than with obvious stimulants. Some pain relievers already include caffeine as an active ingredient: Excedrin Extra Strength carries 65 mg per caplet, 130 mg at its normal two-caplet dose, and taking Vivarin alongside a dose of Excedrin adds up to 330 mg before any coffee or soda. The Vivarin label directs limiting other caffeine-containing medicines, foods and drinks while using it for exactly this reason, and advises asking a doctor or pharmacist first if you’re taking other drugs.
Dosing and limits
The label allows one tablet every 3 to 4 hours as needed, not to exceed the directions on the package, and says not to use it in children under 12 or as a substitute for sleep. The FDA’s warning about concentrated caffeine sources is a useful anchor here too: it estimates toxic effects can appear around 1,200 mg taken rapidly, six tablets’ worth, a dose that a day of stacking Vivarin against a headache and a poor night’s sleep could approach faster than it looks.