context: Insulin is a hormone that your pancreas makes to allow cells to use glucose. When your body isn't making or using insulin correctly, you can take man-made insulin to help control your blood sugar. Many types can be used to treat diabetes. They're usually described by how they affect your body. Rapid-acting insulin starts to work within a few minutes and lasts for a couple of hours. Regular- or short-acting insulin takes about 30 minutes to work fully and lasts for 3 to 6 hours. Intermediate-acting insulin takes 2 to 4 hours to work fully. Its effects can last for up to 18 hours. Long-acting insulin can work for an entire day. Your doctor may prescribe more than one type. You might need to take insulin more than once daily, to space your doses throughout the day, and possibly to also take other medicines. Many people get insulin into their blood using a needle and syringe, a cartridge system, or pre-filled pen systems. The place on the body where you give yourself the shot may matter. You'll absorb insulin the most consistently when you inject it into your belly. The next best places to inject it are your arms, thighs, and buttocks. Make it a habit to inject insulin at the same general area of your body, but change up the exact injection spot. This helps lessen scarring under the skin. Inhaled insulin, insulin pumps, and a quick-acting insulin device are also available. It will depend on the type of insulin you use. You want to time your shot so that the glucose from your food gets into your system at about the same time that the insulin starts to work. This will help your body use the glucose and avoid low blood sugar reactions. For example, if you use a rapid-acting insulin, you'd likely take it 10 minutes before or even with your meal. If you use regular- or intermediate-acting insulin, you should generally take it about a half-hour before your meals, or at bedtime. Follow your doctor's advice. The major ones include: Low blood sugar Weight gain when you first start using it Lumps or scars where you've had too many insulin injections Rash at the site of injection or, rarely, over your entire body With inhaled insulin, there's a chance that your lungs could tighten suddenly if you have asthma or the lung disease COPD. Always have two bottles of each type you use on hand. You don't need to refrigerate vials of insulin that you're using. A good rule of thumb is that if the temperature is comfortable for you, the insulin is safe. You can store the bottle that you're using at room temperature (not higher than 80 F) for 30 days. You don't want it to get too hot or too cold, and keep it out of direct sunlight. You should keep your extra backup bottles in the refrigerator. The night before you're going to start using a new bottle, take it out and let it warm up. Don't let your insulin freeze. Always look at your insulin inside the bottle before you draw it into the syringe. Rapid-acting, short-acting, and certain long-acting types should be clear. Other forms may look cloudy, but they shouldn't have clumps. If you carry a bottle with you, be careful not to shake it. That makes air bubbles, which can change the amount of insulin you get when you withdraw it for an injection. For insulin pens, check the package insert for storage instructions Check the directions on the package. You should keep a sealed package in the refrigerator until you're ready to start using it. If you don't, you must use it within 10 days. You can refrigerate packages you've opened, but let a cartridge warm up to room temperature for 10 minutes before you use it.