Short answer: Low blood sugar (hypoglycemia) is the main Increlex side effect: in the label's trials, 30 of 71 children (42%) had it at least once, 5 had severe episodes and 4 had seizures or loss of consciousness. Enlarged tonsils came next, in 11 children (15%). The label also lists allergic reactions, injection site fat changes, ear problems and headache. There is no boxed warning.
What Increlex is approved for: Increlex is man-made IGF-1 approved for growth failure in children 2 years and older with severe primary IGF-1 deficiency (height SDS and IGF-1 SDS of -3.0 or lower with normal or high growth hormone), or with growth hormone gene deletion who have developed neutralizing antibodies to growth hormone. It is not a substitute for growth hormone and not for secondary IGF-1 deficiency (section 1).
Source
INCRELEX (mecasermin) injection, for subcutaneous use, prescribing information and Patient Information. Eton Pharmaceuticals. DailyMed, version published May 20, 2026. DailyMed setid d5b2b0e1-c523-468d-9a0b-4ae4e4a8dbce
No. The current Increlex 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 Increlex.
| Reaction | Children on Increlex (of 71) |
|---|---|
| Hypoglycemia at least once | 30 (42%) |
| Severe hypoglycemia (needing assistance and treatment) | 5 |
| Hypoglycemic seizures or loss of consciousness | 4 |
| Tonsillar hypertrophy in the first 1 to 2 years | 11 (15%) |
| Tonsillectomy or tonsillectomy/adenoidectomy | 7 |
| Intracranial hypertension | 3 |
There was no placebo or untreated group, so the label gives counts on Increlex only. No child withdrew from any study because of side effects.
Reactions in 5% or more of the 71 children, by body system: low blood sugar; fat buildup at injection sites (lipohypertrophy) and bruising; middle ear infections and fluid; snoring and enlarged tonsils; headache, dizziness and convulsions; vomiting; hearing loss, ear pain and abnormal ear tests; heart murmur; joint and limb pain; enlarged thymus; and ear tube insertion.
Of the 30 children with low blood sugar, 14 (47%) had a history of it before treatment. It was most frequent in the first month and in younger children, and symptoms were generally avoided by eating within about 20 minutes of the dose.
Kidney and spleen size grew quickly in the first years and then slowed, with normal kidney function in all patients. Mild AST and LDH rises, raised cholesterol and triglycerides, heart enlargement or valve changes in a few, and thickening of facial soft tissue were also seen.
After approval, the estimated rate of reactions suggesting anaphylaxis was 0.3%, with hives, swelling and trouble breathing; some needed hospital care. Other reports: injection site itching and hives, hair loss or texture change, injection site reactions, osteonecrosis, and tumors.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Low blood sugar. Increlex has insulin-like effects, and severe hypoglycemia with seizures has happened. It is given within 20 minutes before or after a meal or snack and not given if the meal is skipped. High-risk activities such as driving or exercise are avoided for 2 to 3 hours after a dose, especially early in treatment.
Allergic reactions including anaphylaxis. Reactions range from injection site reactions to anaphylaxis needing hospital care. If a whole-body allergic reaction happens, treatment is interrupted and prompt medical attention sought.
Raised pressure in the skull. Intracranial hypertension with optic nerve swelling, vision changes, headache, nausea or vomiting has occurred and resolved after dosing was paused. Eye exams are recommended at the start and periodically.
Enlarged tonsils and adenoids. Lymphoid tissue growth with snoring, sleep apnea and chronic middle-ear fluid has been reported, so periodic exams are done.
Hip problems. Slipped capital femoral epiphysis, sometimes with bone death (osteonecrosis), has been reported, including with Increlex. A child with a new limp or hip or knee pain is evaluated.
Scoliosis. Scoliosis may progress during rapid growth, so children with scoliosis are monitored.
Malignant tumors. Several cancers have been reported in children after approval, mostly in children with genetic conditions or other factors that raise cancer risk, and more often at higher than recommended doses or with IGF-1 above normal. Increlex is stopped if cancer develops.
Benzyl alcohol in infants. The benzyl alcohol preservative has been linked to serious and fatal "gasping syndrome" in newborns and infants, so Increlex is not recommended in infants.
Who should not use it. Children allergic to mecasermin or its ingredients, those whose growth plates have closed, and those with cancer or a history of cancer.
From the Patient Information leaflet that comes with Increlex:
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.