You need test strips to measure blood sugar. You place a drop of blood on a strip that can be analyzed by the glucose meter. You get the drop of blood by using one lancet on the lancing device. You can only use a strip once. This will give you a pure glucose reading.
Strips are sold in packs of 50. This allows you to take 50 measurements. In one package you will find 2 packs of 25 pieces. The reason for this is the expiration date. Test strips have a maximum expiry date in which they can be used validly. The best-before date can be found on the packaging. Do not use a strip after the expiration date because the measurement will not be reliable.
Test strips are a hygiene product. Once the seal has been broken, the product cannot be returned.