Since blood production requires iron, you should eat iron-rich foods for two weeks before your appointment. This will help you have strong blood for donation and help you better recuperate after your donation. Iron-rich foods include spinach, whole grains, fish, poultry, beans, organ meat, eggs, and beef.
To calculate the change in temperature, subtract the initial temperature from the final temperature. Example: 84.2 degree Fahrenheit - 41 degrees Fahrenheit = 43.2 degrees Fahrenheit. The temperature from morning to afternoon changed by 43.2 degrees Fahrenheit.
As you already know, Celsius, Fahrenheit and Kelvin are the units for measuring temperature. A temperature value can be expressed in any one or all of the above units independently. The values can be converted from one unit to other unit still keeping the meaning same.