What is Lantus® (insulin glargine injection)?

Insulin is a hormone that is naturally produced in our body that works by lowering blood sugar (glucose) levels in the blood. For those who do not produce enough insulin require taking an insulin analog which is a man-made form of insulin.

Lantus is a brand name of insulin glargine taken by adults and children at least 6 years of age with type 1 (insulin-dependent) or type 2 (non insulin-dependent) diabetes.

Lantus is known as a basal insulin (or baseline) which is slowly released evenly throughout the day without spikes as seen with other insulin analogs.

A Lantus treatment may sometimes need the support of a bolus insulin or fast-acting insulin that reduces blood sugar spikes after meals.

This long-acting insulin is injected under the skin (subcutaneously) and helps manage blood sugar levels. It’s formulation of micro-crystals slowly release insulin and provide patients a steady and long-term baseline that starts to work after several hours and works continuously up to 26 hours.


A side effect is any unwanted response from taking medication in regular doses.

Side effects associated with taking Lantus can range from mild to severe. The lists below do not cover all possible side effects. If you are concerned about the potential risks of taking this medication, speak to your doctor.

Seek medication attention immediately if you experience:

  • redness or swelling
  • itchy rash all over your body
  • difficulty breathing
  • swelling of the tongue and throat
  • rapid heartbeat
  • feeling like you may lose consciousness

Consult your doctor if you are experiencing:

  • swelling of hands and feet
  • feeling short of breath
  • weight gain
  • signs of low potassium (leg cramps, irregular heartbeat, increased thirst or urination, muscle weakness or feeling limp, numbness or tingling, fluttering in your chest.

Common side effects from using Lantus include:

  • low blood sugar
  • thickening or hollowing of skin at site of injection
  • mild skin rash
  • itching
  • edema (swelling)
  • respiratory infections
  • hypoglycemia (low blood glucose levels)
  • injection site reactions

These side effects are typically temporary and go away after a few days or weeks. If they don’t go away and become more severe, speak to your doctor or pharmacist.

Serious Side Effects

While serious side effects aren’t common, they can occur. Symptoms can include:

  • allergic reaction
  • abnormal heart beat
  • fatigue
  • Hypokalemia (low potassium levels)
  • weakness
  • muscle cramping
  • paralysis
  • severe hypoglyecemia
  • allergic reactions
  • respiratory failure

Side effects in detail

The following common side effects are associated with Lantus in more detail.

Allergic Reactions

Some may experience allergic reactions when taking Lantus. Make sure you do not have an allergy to any ingredients in this solution.

Mild allergic reactions may include:

  • flushing
  • itchiness
  • skin rash (red and warm skin)

Severe allergic reactions may include:

  • difficulty breathing
  • full body rash
  • swelling of the mouth, tongue or throat
  • swelling under the skin (typically lips, hands, feet or eye lids)

Consult your doctor immediately if you experience any severe allergic reactions while taking Lantus insulin. Call 911 and seek medical emergency if you feel the symptoms are life threatening.

Weight Gain

One of the most common side effects while taking Lantus is weight gain since the body stores sugar for energy. The average weight gained according to clinical studies was:

  • up to 1.5 lb in adults with type 1 diabetes who took Lantus over 16-28 weeks
  • up to 4.8 lb in children with type 1 diabetes who took regular insulin with Lantus for 28 weeks
  • up to 4.4 lbs in adults with type 2 diabetes who took Lantus for 1 year

If weight gain is a concern, speak to your doctor on how to better manage your weight.


Hypoglycemia (low blood sugar) is the most common side effect with any insulin such as Lantus.

It’s important to monitor your blood sugar levels so you can address a hypo before it becomes severe.

Mild hypoglycemia symptoms include:

  • rapid heartbeat
  • shakiness
  • nervousness
  • shakiness
  • dizziness
  • headache
  • hunger

If blood sugar levels remain too low, symptoms may worsen and require medical attention.

Severe hypoglycemia symptoms include:

  • anxiety
  • drowsiness
  • fast heartbeat
  • hunger
  • headache
  • irritability
  • sweating
  • confusion
  • seizures
  • coma

Any changes to your insulin treatment should be under the guidance of a doctor. Any adjustments to insulin dosage could put you at risk of hypoglycemia or hyperglycemia.

How common is hypoglycemia?

  • A 16-week clinical study with adults with type 1 diabetes taking Lantus found 6.5% of adults experienced hypoglycemia at least once.
  • A 28-week study found 10.6% of the adults experienced hypoglycemia at least once.
  • A 5-year clinical study involving adults with type 2 diabetes taking Lantus with regular insulin resulted in 7.8% experiencing hypoglycemia
  • A study examining children with type 1 diabetes taking Lantus found that 23% experienced severe hypoglycemia over a 6-month period

How to treat hypoglycemia?

If you experience hypoglycemia (blood sugar levels drop too low) try to consume fast-acting carbohydrates. By consuming a sugary snack or beverage you can raise your blood sugar levels quickly. Things you can eat during a hypo can include:

  • glucose tablet
  • honey
  • hard candy
  • fruit juice
  • pop (non diet)
  • saltine crackers
  • jelly beans

If you are experiencing frequent episodes of hypoglycemia then you should consult with your doctor. They may recommend a prescription for glucagon which is a hormone that quickly raises your glucose levels, especially during an emergency such as loss of consciousness where you cannot consume glucose orally.


Do not use Lantus to treat diabetic ketoacidosis (DKA).

Do not take Lantus if you are allergic to insulin or any of its ingredients. Lantus can lead to serious side effects and even death in severe allergic reactions. Seek medical attention immediately if you experience:

  • full body rash
  • difficulty breathing/shortness of breath
  • sweating
  • swelling of face, throat or tongue
  • rapid heartbeat
  • extreme dizziness, drowsiness or confusion

Lantus may cause serious side effects that can lead to death, such as severe allergic reactions. Get medical help right away if you have:

Do not take Lantus if you are experiencing signs of hypoglycemia.

Do not share insulin pens, syringes or needs with others as this can lead to spreading infection or blood pathogens. Do not reuse needles.

Inform your doctor if you have any pre-existing medical conditions such as liver or kidney problems, are pregnant or planning on becoming pregnant or breastfeeding.

Rotate injection sites to avoid developing lipodystrophy (thickened or pitted skin) or amyloidosis (lumps on skin) at the site of injection. Try to not use the same spot repeatedly for injection or injected where skin is tender, bruised, scarred, lumpy, pitted, thickened or damaged.

Heart failure can occur if you are taking Lantus with other medications such as TZD (thiazolidinediones) even if you have never experienced heart problems in the past. If you have an existing heart condition, your treatment may need to be modified by your doctor to avoid complications.

Notify your doctor if you have any symptoms of heart failure including:

  • swelling of ankles and feet
  • sudden weight gain
  • shortness of breath or difficulty breathing

Inform your doctor about all medications you are currently taking including other prescription medications, over-the-counter medications, vitamins, minerals and herbal supplements.

Lantus should be taken at the same time once daily. Monitor and test blood sugar levels while using insulin. Do not make any adjustments to dosage without consulting your doctor first as this can lead to severe complications.

Do not dilute or mix Lantus with other insulin or solutions otherwise it will not work as intended and you may lose blood glucose control.

Lantus should only be used if the solution appears clear and colorless. Do not use if it contains particles.

Check the label on the vial or carton before injection to ensure you are using the correct insulin your doctor has prescribed.

Do not drive or operate heavy machinery while using Lantus.

Do not consume alcohol or use medications that include alcohol while using Lantus as this can affect blood sugar levels.

The most common side effect when using insulin is hypoglycemia which can be serious and life threatening. If not treated properly can affect your heart or brain. Pay attention to hypoglycemia symptoms mentioned above.

For more information read the leaflet below, consult a doctor or speak with your pharmacist.