Short answer: Low blood sugar (hypoglycemia) is the most common Toujeo side effect, as with all insulin. In the label's adult trials, the other reactions at 5% or more were nasopharyngitis (12.8% in type 1, 7.1% in type 2 diabetes) and upper respiratory infection (9.5% and 5.7%). Severe low blood sugar affected 1.0% to 6.6% of adults depending on the study. Toujeo has no boxed warning.
What Toujeo is approved for: Toujeo is a long-acting insulin approved to improve blood sugar control in adults and children 6 years and older with diabetes (section 1). It is not recommended for treating diabetic ketoacidosis.
Source
TOUJEO (insulin glargine) injection, for subcutaneous use, 300 units/mL, prescribing information, Patient Information and Instructions for Use. Sanofi-Aventis U.S.. DailyMed, version published June 12, 2025. DailyMed setid c9561d96-124d-48ca-982f-0aa1575bff36
No. The current Toujeo label has no boxed warning.
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Toujeo.
| Adverse reaction | TOUJEO + mealtime insulin, % (n=304) |
|---|---|
| Nasopharyngitis | 12.8 |
| Upper respiratory tract infection | 9.5 |
Toujeo plus mealtime insulin (glulisine, lispro or aspart). The table shows Toujeo only; it has no comparator column. Mean exposure was 23 weeks.
| Adverse reaction | TOUJEO, % (n=1242) |
|---|---|
| Nasopharyngitis | 7.1 |
| Upper respiratory tract infection | 5.7 |
One of the three trials included mealtime insulin. Toujeo only; no comparator column. Mean exposure was 25 weeks.
| Group | Severe hypoglycemia, % | Glucose below 54 mg/dL, % |
|---|---|---|
| Adults, type 1, multiple daily injections | 6.6 | 77.7 |
| Children 6-17, type 1, multiple daily injections | 6 | 80.3 |
| Adults, type 2, multiple daily injections | 5 | Not given per study; 9 to 44.6 across type 2 studies, highest with multiple daily injections |
| Adults, type 2, basal insulin only (two studies) | 1.0 and 0.9 | Not given per study |
In adults, severe meant needing another person to give a resuscitative action. In children, it meant semiconsciousness, unconsciousness, coma or convulsions with inability to self-treat.
Toujeo was studied in 233 children aged 6 to 17 with type 1 diabetes for a mean of 26 weeks; their common side effects were similar to Table 1.
Injection site redness, swelling and itching were reported and were usually self-limiting. Severe whole-body allergy (anaphylaxis) has been reported.
Rapid improvement in blood sugar has been linked to a temporary, reversible vision refraction change, worsening of diabetic retinopathy and acute painful nerve pain. Weight gain and swelling from sodium retention can also occur.
In a 6-month type 1 study, 79% on Toujeo tested positive for anti-insulin antibodies at least once (62% were positive at baseline). In two 6-month type 2 studies the figure was 25% (42% positive at baseline).
Reported after approval: localized cutaneous amyloidosis (lumps under the skin) at injection sites. Injecting into those lumps has raised blood sugar, and a sudden switch to normal skin has lowered it.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not use it. Toujeo is not used during an episode of low blood sugar, or by people allergic to insulin glargine or its ingredients.
Never share a pen. A Toujeo SoloStar or Max SoloStar pen is never shared, even if the needle is changed, because of the risk of passing on blood-borne infections.
Changes in insulin regimen. Changing insulin strength, maker, type, injection site or method can cause high or low blood sugar, so changes are made under close supervision with more glucose checks. Unit for unit, Toujeo lowers glucose less than Lantus, and people switching to it needed higher doses in trials. Its action builds over 6 hours, and the full effect may take at least 5 days.
Low blood sugar. Hypoglycemia is the most common reaction to insulin, and severe episodes can cause seizures or death. Toujeo's long action may delay recovery from a low. Awareness of lows may be reduced with long diabetes, nerve damage, beta-blockers or repeated lows.
Medication mix-ups. Mix-ups between insulin products have been reported, so the insulin label is checked before each injection. Toujeo is never drawn out of the pen with a syringe, which can lead to an overdose.
Serious allergic reactions. Severe, life-threatening whole-body allergy, including anaphylaxis, can occur; Toujeo is stopped if it does.
Low potassium. All insulins shift potassium into cells and can cause low potassium, which untreated can cause breathing paralysis, heart rhythm problems and death.
Heart failure with TZDs. Thiazolidinediones (such as pioglitazone) with insulin can cause fluid retention that may lead to or worsen heart failure.
From the Patient Information that comes with Toujeo:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.