Key takeaways

Lantus, a long-acting insulin, is used for blood sugar control in diabetes, but not usually the first choice for Type 2 diabetes due to side effects like weight gain and hypoglycemia.
Common side effects of Lantus include hypoglycemia, weight gain, injection site reactions, and potentially severe allergic reactions.
Lantus should be used with caution, avoiding overdose and considering interactions with other medications, under the guidance of a healthcare professional to manage and minimize side effects.
To avoid Lantus side effects, follow medical advice on dosing, monitor blood sugar levels closely, rotate injection sites, and be aware of symptoms of hypoglycemia.

Insulin therapy for diabetes treatment attempts to mimic the body’s natural insulin secretion. Lantus, a brand-name version of glargine insulin like Basaglar and Toujeo, is frequently helpful in gaining blood sugar control in diabetes. Naturally, a healthy pancreas secretes a continual supply of insulin and responds to meals with extra amounts of insulin. In the setting of diabetes mellitus, Lantus can be injected once a day, is slowly absorbed into the bloodstream, and provides a long-acting insulin supply for approximately 24 hours. This therapeutic option may need to be complemented by short-acting insulin to provide the extra insulin at mealtimes. Lantus and other insulins are not usually the first choice for Type 2 diabetes mellitus management, partially due to side effects. While insulin treatment is necessary for Type 1 diabetes mellitus, Lantus and other varieties must be used with an understanding of the possible adverse effects.

Common side effects of Lantus

The following are commonly reported Lantus side effects:

Hypoglycemia (low blood sugar)
Weight gain
Injection site lipodystrophy
Injection site reaction, skin rash, or pruritus (itching)
Myalgia (muscle pains)
Upper respiratory infection or influenza
Headache
Peripheral edema (swelling in arms or legs)
Hypersensitivity allergic reaction

Weight gain

Glargine has the potential to be associated with weight gain, as do other insulins, for multiple reasons. First of all, insulin has an anabolic (tissue-building) effect on the body, and secondly, a reduction in glucose level results in less glucose loss in the urine and more storage in the body. Behavioral factors also contribute, namely continued dietary indiscretion and increased intake to stave off hypoglycemia.

In one study, Lantus users averaged three to eight pounds of weight gain. By comparison, study participants taking an alternative long-acting or basal insulin Levemir (detemir) gained two pounds less on average.

Rapid weight gain when taking insulin is more alarming and may be a sign of peripheral edema, or fluid retention, most often in the lower legs.

Serious side effects of Lantus

Hypoglycemia
Severe hypersensitivity allergic reactions including anaphylaxis
Hypokalemia (low potassium)

Hypoglycemia

When blood sugar levels run low, the extent of symptoms depend largely on the degree of hypoglycemia. Sugars below 70 mg/dL are typically considered abnormally low. Values under 65 mg/dL commonly cause symptoms, but the threshold for causing symptoms varies from one person to the next. For example, those with poorly controlled diabetes may experience symptoms at higher glucose values since their systems are not accustomed to normal sugar levels. With mild degrees of hypoglycemia, which occur commonly with Lantus and other insulins, one may feel effects such as shakiness, palpitations, tachycardia (fast heartbeat), sweating, dizziness, blurred vision, drowsiness, or hunger. These are expected to resolve when sugar is consumed, such as after eating crackers or juice.

More severe degrees of hypoglycemia may elicit drowsiness and confusion, or at the extreme, seizures or coma. These symptoms make a bad situation worse by impairing one’s recognition of the problem, awareness of the solution, and the ability to eat or drink. Serious hypoglycemia is often defined as a level that requires the assistance of another person to help reverse it. These efforts may be administering a sugary drink or could be an injection of glucagon, a prescription product that temporarily raises blood sugar.

The symptoms of hypoglycemia are an important warning sign to recognize, both by users of insulin and their family and friends. The need for everyone to understand these symptoms is based on the fact that people with diabetes may have unawareness of their hypoglycemia for multiple reasons. Hypoglycemic unawareness can occur due to autonomic nervous system dysfunction due to diabetes, from the use of beta blocker drugs (blood pressure medication) that blunt symptoms like sweating and tremors, or from having recently exercised. Nocturnal occurrences of hypoglycemia can also be problematic as symptoms typically awaken the individual but possibly not until an even lower blood sugar level is reached.

In the original clinical studies of Lantus for Type 1 diabetes, when used in combination with regular insulin for 28 weeks, severe hypoglycemia occurred in about 8% to 10% of patients. With similar combination therapy and study timeframe for treatment of Type 2 diabetes, Lantus was associated with an incidence rate of less than 1% of severe hypoglycemia. The rates were similar in comparison to NPH, a common intermediate-acting insulin.

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How long do Lantus side effects last?

The duration of adverse effects from Lantus is variable. Weight gain can persist while the drug is continued. Hypoglycemia problems could continue throughout the 24-hour duration of action if the dose taken was too high or dietary intake too low. Hypersensitivity allergic reactions can last from hours to weeks after stopping the medication.

Lantus contraindications and warnings

Abuse and dependence

Lantus is not habit-forming, and discontinuation does not induce a withdrawal syndrome. Stoppage can result in significant hyperglycemia (high blood sugar levels) or, in Type 1 diabetes mellitus, life-threatening diabetic ketoacidosis.

Overdose

Lantus does not have a defined maximum dose. Sensitivity to its effects is highly variable, particularly in Type 2 diabetes in which dosages often need to be higher due to insulin resistance. Careful initiation and adjustment of insulin under the direction of a healthcare professional is of paramount importance. An overdose of Lantus can produce dangerous degrees of hypoglycemia, which in rare cases can be fatal.

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Restrictions

Insulin glargine can be used by most adults with Type 1 or Type 2 diabetes, including seniors.
The Food and Drug Administration (FDA) approval for Lantus in pediatric patients with Type 1 diabetes extends down to age 6.
Pregnant women can use Lantus, since insulin is typically the preferred therapy for Type 1 and Type 2 diabetes during pregnancy, as well as gestational diabetes, when pharmacologic treatment is needed.
Usage of Lantus while breastfeeding should only be done after careful consideration and discussion of possible risks and benefits.

Lantus is contraindicated in the following cases:

In the setting of hypoglycemia or if there is a history of allergic reactions to the drug or class of drugs.
It should not be used intravenously or in insulin pumps.
Caution and potential dosing adjustments may be needed during illness or if concurrent liver or kidney disease or impairment exists.

Lantus interactions

Lantus can interact with a number of medications, mostly via additive side effects, so it is imperative to review your medication list with the prescribing provider. Examples of these interactions include the following:

Medications with additive hypoglycemic potential including diabetes mellitus medications, such as insulins, sulfonylureas, repaglinide, metformin, pioglitazone, GLP-1 agonists, and SGLT2 inhibitors, and non-diabetic medications, such as quinolone antibiotics
Medications with additive effects on peripheral edema, such as pioglitazone and rosiglitazone
Medications with additive hypokalemia potential, such as loop and thiazide diuretics
Alcohol by increasing the risk of hypoglycemia
Beta blockers since they mask the symptoms of hypoglycemia

How to avoid Lantus side effects

Follow the medical advice of a healthcare provider before starting or adjusting Lantus dosing. Double-check the insulin dose each time before administering. Dosing may need to be altered if changing the type of insulin. In particular, if changing from or to Toujeo, understand the difference in concentration between Toujeo and Lantus and how it affects your dosing.
Review your list of prescription drugs, over-the-counter medications, and supplements with the treating practitioner in order to avoid drug interactions. A review of your medical conditions can be helpful to look for risk factors for adverse events.
Before initiating Lantus supplied in vials, have a healthcare professional instruct you on proper use of a needle and syringe to draw up insulin from a vial and then administer. Likewise, if Lantus Solostar is prescribed, ask a healthcare professional to show you how to use this pre-filled glargine insulin pen device.
Have a healthcare professional show you recommended insulin injection sites in the abdomen, upper arm, and upper leg. Or refer to drug information from Sanofi, the drug manufacturer. Rather than using the same site repeatedly, rotate the injection site to reduce the risk of lipodystrophy, a depressed or raised area from changes to subcutaneous tissue. Choose a clean injection site, without scarring, scaliness, or damage.
Use a new needle each time.
Avoid heating or excessively rubbing the injection site after administration as this may affect how quickly the insulin is absorbed and takes effect, including heightening the risk of hypoglycemia.
Use a glucometer, blood sugar monitor, as directed by the provider to assess the degree of blood glucose control. Monitor more closely before, during, and after exercise, as well as during times of illness, stress, surgery, dose changes, or skipped meals.
Do not drink alcohol due to its potential to affect glucose levels.
Understand the symptoms and treatment of hypoglycemia, and educate those around you. Wear a medical alert bracelet identifying you as having diabetes, in case you have a severe hypoglycemic reaction and cannot express what is happening to a bystander.
Store unopened Lantus and Lantus Solostar in the refrigerator, and use it by the expiration date. Alternatively, if Lantus is stored at room temperature, use it within 28 days. Once opened, Lantus and Lantus Solostar must be used within 28 days, and Lantus Solostar must be stored at room temperature.
Do not use insulin that is cloudy in color. Do not mix Lantus with other insulins.
Seek immediate medical care in the event of allergic reaction symptoms such as shortness of breath or trouble breathing.