If I add milk to my coffee and leave it in a thermos for hours how long will last as safe drink not get sick?

Coffee with milk should not be left in a thermos for hours, as it creates a risk of bacterial growth. Milk is a perishable food and must be refrigerated at temperatures below 40 degrees Fahrenheit to prevent harmful bacteria from multiplying.

When coffee with milk is left at room temperature or in a warm environment, bacteria can grow rapidly, making the coffee unsafe to drink. Consuming coffee with spoiled milk can cause foodborne illnesses, leading to symptoms such as stomach cramps, nausea, vomiting, and diarrhea.

Storing coffee with milk in a thermos doesn't prevent bacterial growth because thermoses are designed to insulate and can maintain warmth for hours. Even if the insulation keeps your coffee warm and enjoyable for consumption.

Therefore, for safety reasons, avoid keeping milk-based coffee in a thermos for extended periods and discard any leftover coffee by the following morning if prepared the previous day.