People with diabetes may need daily insulin injections to control their blood sugar levels. Typically, a person will inject insulin before eating. However, this can depend on the type of insulin a person is using.

Diabetes is a condition that can affect a person’s blood glucose levels. Glucose is a form of sugar that comes from the food a person eats and is the body’s main source of energy.

Insulin is a hormone the body needs to move glucose from the blood into cells. If a person has diabetes, their body either does not make enough insulin or cannot use it properly. This causes the glucose to remain in the bloodstream.

A person who has diabetes can use insulin to manage their blood sugar levels, and they will often use insulin before a meal. However, different factors, such as the type of insulin and how the body responds to the dose, mean that people may need their insulin injection after a meal.

Read on to learn more about insulin, including when to take it and other best practices.

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Insulin allows the body’s cells to take glucose from the blood. It also signals a person’s liver to turn excess glucose into glycogen for storage.

If a person has diabetes, they may require insulin therapy. The Centers for Disease Control and Prevention (CDC) notes that different types of insulin can vary in onset and duration. For example, fast-acting insulin a person may use before eating, and long-acting insulin, which a person may use between meals.

The CDC also states that a person can receive insulin in several ways:

  • Injection: A person can use a syringe to inject themselves with a dose of insulin. A doctor will let them know what dose they require.
  • Pen: Insulin pens inject insulin into a person’s bloodstream similarly to injections. They use pre-filled cartridges that a person can dispose of after use.
  • Pump: An insulin pump delivers insulin under a person’s skin via a tube attached to the device. It delivers insulin to the body throughout the day.
  • Inhaler: Insulin inhalers allow a person to take a dose of rapid-acting insulin before a meal. A person can use these inhalers alongside insulin injections.

A person should take insulin as prescribed by a doctor. Different types of insulin need to be taken at different times of the day.

In general, a doctor may suggest a person take different types of insulin in the following ways:

Insulin typeHow long it takes to start workingPeakHow long it lastsHow to take it
rapid-acting15 minutes1 hour2–4 hoursgenerally taken right before a meal; often used with a longer-acting insulin
rapid-acting inhaler10–15 minutes30 minutes3 hoursgenerally taken right before a meal; often used with an injectable, longer-acting insulin
regular/short-acting30 minutes2–3 hours3–6 hoursnormally taken 30–60 minutes before a meal
intermediate-acting2–4 hours4–12 hours12–18 hourscovers insulin requirements for half a day or overnight; usually used with a rapid- or short-acting insulin
long-acting2 hoursdoes not peakup to 24 hourscovers insulin requirements for about a day; usually used with doses of rapid- or short-acting insulin, when needed
ultra long-acting6 hoursdoes not peak36 hours or moreprovides steady amounts of insulin for long periods
pre-mixed; a combination of intermediate- and short-acting insulin5–60 minutespeaks can vary10–16 hoursgenerally taken 10–30 minutes before breakfast and dinner

A 2017 review notes that people with type 1 diabetes who used rapid-acting insulin 15–20 minutes before a meal had a reduction in post-meal glucose levels of around 30% compared to taking insulin immediately before eating. Additionally, they had a lower chance of hypoglycemia, which is when a person’s blood sugar levels are too low.

The American Diabetes Association (ADA) notes that a person should inject insulin into the same general area each time. Insulin can take longer to reach the bloodstream depending on where a person injects it. By injecting it in the same area, a person receives their insulin at the same speed each time.

However, a person should be careful not to inject their insulin into the exact same spot every time. This can cause hard lumps or fatty deposits to occur. These can be unsightly and affect how effective the insulin is.

Read on to learn more about insulin injection sites.

A person can speak with a doctor about the daily amount of insulin they should be taking. Insulin doses can vary depending on factors, such as:

  • the type of diabetes
  • how many carbohydrates a person eats in a day
  • weight
  • activity level
  • appetite and hunger levels

If a person is unsure about how to calculate their insulin dose or how many carbs they should be eating, they can ask a doctor about a diabetes self-management education (DSME) session. The ADA provides a tool that allows people to find programs in their area.

If a person takes too much insulin, they can become hypoglycemic.

The ADA recommends that people with hypoglycemia have 15 grams (g) of carbohydrates and then check their blood sugar levels after 15 minutes. This is known as the “15-15 rule.” A person should continue this method until their levels are 70 milligrams per deciliter (mg/dL) or higher.

The ADA recommends the following carbs to increase blood sugar:

  • glucose tablets
  • hypoglycemia gel
  • half a cup of juice or non-diet soda
  • 1 tablespoon of honey, corn syrup, or sugar
  • hard candies, jellybeans, or gumdrops

If a person has severe hypoglycemia, they may require a glucagon injection. This hormone helps release glucose stored in the body. If there is no glucagon available, a person should seek emergency medical attention.

If a person does not take enough insulin, they can develop hyperglycemia. Long periods of hyperglycemia can result in a condition known as diabetic ketoacidosis. This is when the body breaks down fats too quickly. If a person’s blood sugar levels are too high, they can administer a correction dose of insulin to bring them within the target range.

Exercise can also help lower a person’s blood sugar levels. However, a person should test their urine for ketones before exercising. If ketones are present, a person should not exercise as it may increase their blood sugar levels.

Other best practices for insulin use include:

  • never sharing needles
  • not reusing needles, where possible
  • using the shortest needle possible
  • washing hands before injecting
  • cleaning the injection site before injecting, when required
  • talking to friends and family about insulin
  • only injecting into fat tissue
  • regularly checking blood sugar levels and noting measurements
  • always consulting a doctor before switching insulin or stopping taking it

A person should also know the symptoms of hypoglycemia and let their family and friends know what symptoms to look out for. Symptoms of hypoglycemia include:

  • shakiness
  • nervousness
  • anxiety
  • sweating, chills, and clamminess
  • irritability or impatience
  • confusion
  • a rapid heartbeat
  • hunger
  • nausea
  • paleness
  • sleepiness
  • feeling weak
  • blurred or impaired vision
  • tingling or numbness
  • headaches
  • clumsiness
  • nightmares or crying out during sleep
  • seizures

Read on to learn more about treating a hypoglycemic episode.

The kind of insulin a person takes can depend on the type of diabetes they have. Typically, it is advisable for a person to take faster-acting insulin before they have a meal to help manage their blood sugar levels.

If a person needs help figuring out what dose of insulin to take, they can speak with a doctor. Additionally, they can ask a doctor to refer them to a diabetes self-management education program.