Mecasermin

What Mecasermin does

Mecasermin copies human IGF-1 and is approved as Increlex for specific rare causes of childhood growth failure. Adult muscle-building and longevity benefits are unproven. Growth studies and safety registries support its childhood use. It can cause severe low blood sugar and unwanted tissue growth.

• Increlex is approved for children age 2 and up whose poor growth comes from severe primary IGF-1 deficiency. (Drug label)
• In a registry of treated patients, final height improved, especially when treatment began before puberty. (Studied in a trial)
• In a small controlled study, it helped growth in people whose bodies cannot respond to growth hormone. (Studied in a trial)

Uses in the sources

• FDA-approved from age 2 for growth failure due to severe primary IGF-1 deficiency, or GH gene deletion with neutralizing GH antibodies. (Drug label) (source)
• Studied for ALS, Rett syndrome, Phelan-McDermid syndrome, diabetes and other conditions. These are not FDA-approved indications. (Studied in a trial) (source)
• Bodybuilding forums discuss Increlex, often confusing it with LR3 or an IGF-1/IGFBP-3 complex. Benefits and product identity are uncertain. (Reported by users) (source)

Mecasermin dosage

Typical reported dose: 0.04 mg per kg twice a day to start, up to 0.12 mg per kg

• US label, 0.04 mg/kg start: 0.04 mg/kg per dose twice daily for at least 1 week, then If tolerated, 0.08 mg/kg per dose twice daily for at least 1 week, then If tolerated, up to 0.12 mg/kg per dose twice daily twice daily, under the skin. Drug label. Studied in: FDA-labelled pediatric growth-failure indications, age 2 and older. (source)
• US label, 0.08 mg/kg start: 0.08 mg/kg per dose twice daily for at least 1 week, then If tolerated, up to 0.12 mg/kg per dose twice daily twice daily, under the skin. Drug label. Studied in: FDA-labelled pediatric growth-failure indications, age 2 and older. (source)
• EU label, 0.04 mg/kg start: 0.04 mg/kg per dose twice daily for at least 1 week, then If no significant adverse reactions, 0.08 mg/kg twice daily, then If tolerated after at least another week, maximum 0.12 mg/kg twice daily twice daily, under the skin. Drug label. Studied in: Children/adolescents ages 2–18 with severe primary IGF-1 deficiency. (source)
• Clinician-published cautious start: 0.04 mg/kg per dose twice daily in younger or hypoglycemia-prone children, then Increase more slowly as tolerated toward 0.1–0.12 mg/kg per dose twice daily; no fixed weekly schedule twice daily, under the skin. Clinician-published. Studied in: Children with confirmed severe primary IGF-1 deficiency. (source)
• Growth study, 80 mcg/kg: 80 mcg/kg per dose, twice daily twice daily, under the skin. Studied in a trial. Studied in: Children with GH receptor deficiency. (source)
• Growth study, 120 mcg/kg: 120 mcg/kg per dose, twice daily twice daily, under the skin. Studied in a trial. Studied in: Children with GH receptor deficiency. (source)

These are doses reported in labels, trials or user reports, not a personal plan. Check the source behind each one.

Work out syringe units with the dosing calculator

How to store Mecasermin

Comes as: Sterile, ready-to-use solution in a multidose glass vial.

Mixed with: None. Increlex is a ready-to-use 10 mg/mL solution. Do not add water..

Common vial sizes: 40 mg. Common water amounts: mL.

• Each vial holds 40 mg in 4 mL of solution, not powder.
• Discard expired or frozen vials. Do not use cloudy, discolored or particle-containing solution.
• Syringe units measure volume, not IGF-1 strength. Have your pharmacist check the markings against your prescription.

Before mixing: Unopened: refrigerate at 2–8°C, away from direct light. Do not freeze.

After mixing: After first puncture: refrigerate at 2–8°C, away from direct light. Discard after 30 days.

Mecasermin side effects and risks

Reported side effects

• Low blood sugar: FDA pool: 30/71, 42%; 5 had severe episodes and 4 had seizures or loss of consciousness., serious. Link doses to food and monitor glucose. Lower the dose if episodes occur despite adequate food. (source)
• Tonsil or adenoid growth: FDA pool: tonsillar growth in 11/71, 15%; 7 required surgery., moderate. Assess new snoring, sleep pauses, swallowing problems or ear symptoms. (source)
• Injection-site fat growth: 32% in the separate 76 patient long term cohort; not the FDA 71 patient pool., mild. Rotate injection sites. (source)
• Headache or vomiting: Each reported in ≥5% in the FDA pool; exact separate rates are not given there., moderate. Persistent severe headache, vomiting or visual changes need urgent assessment. (source)
• Raised pressure around the brain: FDA pool: 3/71 had intracranial hypertension., serious. Eye examination at baseline and periodically; assess new headaches or vision changes. (source)
• Severe allergic reaction: Postmarketing anaphylaxis estimate 0.3%; voluntary reports have uncertain denominators., serious. Stop and seek emergency care for breathing trouble or facial swelling. (source)
• Joint pain, bruising or ear problems: Individual listed reactions occurred in ≥5% in the FDA pool; precise rates not supplied., moderate (source)
• Edema and jaw pain: Higher dose type 1 diabetes arms had unacceptable rates; exact rates not extracted., moderate (source)
• Worsening diabetic eye disease: 11/55 in a younger type 1 diabetes subset; this does not estimate risk in all users., serious (source)
• Benign or malignant growths: Postmarketing cases reported. Causation and a reliable cancer incidence are unknown., serious. New lumps, changing moles or other growths need prompt medical review. (source)
• Hip growth-plate slip or bone tissue death: Reported in children; frequency unknown., serious. New limp or hip/knee pain needs prompt evaluation. (source)
• Benzyl-alcohol toxicity in neonates and infants: The label warns of serious and fatal reactions with benzyl alcohol preserved drugs; this is not an incidence estimate for Increlex., serious. Increlex contains 9 mg/mL benzyl alcohol. Its label does not recommend use in infants; safety and effectiveness below age 2 are not established. (source)

Stop and get help if

• Confusion, seizure, fainting or persistent low blood sugar: Stop dosing and get emergency care. Do not give food or drink to an unconscious person.
• Breathing trouble, throat/facial swelling or widespread hives: Stop dosing and get emergency care.
• Severe or persistent headache, vomiting or new vision changes: Stop dosing and seek urgent evaluation for raised pressure around the brain.
• New limp or hip/knee pain: Get prompt care for hip growth-plate slip or bone tissue death.
• Chest pain, collapse or severe breathlessness: Get emergency care now.
• New or changing lump, mole or other abnormal growth: Stop dosing and arrange prompt specialist assessment.

Who should avoid it

• under18: Increlex itself is approved from age 2; this app block is not an FDA pediatric contraindication.
• pregnant: No adequate human pregnancy data. The EU label says not to use during pregnancy.
• breastfeeding: Milk transfer and infant effects are unknown.
• tryingToConceive: This is a precaution. The EU label advises pregnancy testing and contraception during treatment.
• activeCancer: Active or suspected neoplasia is a stop condition. Discontinue if a tumor develops.
• cancerHistory: The US label excludes pediatric patients with prior malignancy; EU/UK restrictions include cancer-predisposing history.
• other: Do not re-expose after a serious reaction to mecasermin or an ingredient.
• other: Do not use for height gain after growth plates close. Adult bones cannot lengthen through this mechanism.
• other: Food must be available around each dose. Withhold a dose when the meal or snack is omitted.
• diabetes: Glucose-lowering treatment may need adjustment; low blood sugar can be severe.
• diabeticRetinopathy: One IGF-1/insulin trial reported early retinal worsening at higher doses.
• seizureDisorder: Hypoglycemia can cause seizures or loss of consciousness.
• sleepApnea: Tonsil/adenoid enlargement may worsen snoring or obstructed breathing.
• heartCondition: Fluid retention and cardiac changes warrant review; cardiac causation in growth studies was uncertain.
• kidneyDisease: No established dose adjustment for children with primary IGF-1 deficiency and kidney disease.
• liverDisease: No established dose adjustment for children with primary IGF-1 deficiency and liver disease.
• surgeryPlanned: Fasting may require withheld doses and adjusted glucose-lowering treatment.
• other: Raised brain pressure is a risk; eye checks are recommended before and during treatment.
• other: Rapid growth can worsen an existing spinal curve.
• testedAthlete: WADA prohibits mecasermin at all times under S2.3.

Interactions

• Insulin: Doses may need reduction because of additive low blood sugar. Insulin co-treatment in trials required close glucose checks.
• Sulfonylureas and other insulin releasers: Other glucose-lowering medicines may need reduction. No formal interaction study defines a dose change.
• Other IGF-1 products: No safe schedule is established for combining IGF-1 products.
• Growth hormone and secretagogues: Pediatric GH combinations were studied in selected patients; this does not establish a safe adult or secretagogue stack.
• Anticoagulants and antiplatelets: No interaction studies are available. Injection-site bruising and bleeding have been reported.

Product quality risks

• Unregulated IGF-1 analogues are not interchangeable with licensed mecasermin. A tested LR3 vial contained an extra purification tag.
• No current market-wide survey of counterfeit or underdosed Increlex was located. Specific counterfeit-pen rates are unknown.
• A research-use-only label or purity percentage does not establish identity, amount, sterility or freedom from endotoxin.

What to expect

At least 106 human research reports were found, including case reports and studies that reuse participants. These are not 106 separate trials.

Key studies

• FDA pooled growth studies: Growth increased in a rare pediatric population; most studies lacked a control group. (source)
• Early European replacement study: Early replacement studies showed growth and glucose effects. (source)
• Laron syndrome over three years: Once-daily native IGF-1 improved growth in a small early cohort. (source)
• Ecuador placebo-controlled growth trial: Controlled evidence supports growth effects in GH receptor deficiency. (source)
• 80 versus 120 mcg/kg: The higher dose did not improve measured growth in this small comparison. (source)
• European long-term growth: Growth gains persisted, but most patients remained very short. (source)

Mecasermin FAQ

• Is Mecasermin FDA-approved? Yes: Increlex (growth failure from age 2 due to severe primary IGF-1 deficiency, or GH gene deletion with neutralizing GH antibodies.). Not approved for adult bodybuilding, anti-aging, secondary IGF-1 deficiency or replacement of GH for GH indications.
• How do people take it? Under the skin, twice daily. Source: drug label.
• What's the difference between Mecasermin and Somatropin? Mecasermin: prescription IGF-1 approved for rare childhood growth failure; low blood sugar is a major risk. Somatropin: prescription human growth hormone, with no proven anti-aging benefit. Why people pair them: pediatric researchers tested whether combined replacement increases height velocity.
• Can I take it with Growth hormone? Pediatric researchers tested whether combined replacement increases height velocity. This selected pediatric study does not validate adult bodybuilding combinations. Source: studied in a trial. Ask a doctor before combining anything.
• Is it banned in sport? Yes. It is banned in and out of competition (WADA 2026). IGF-1, mecasermin and IGF-1 analogues are prohibited in and out of competition.
• How do I store it once opened? After first puncture: refrigerate at 2–8°C, away from direct light. Discard after 30 days.