Somatropin Side Effects: What to Expect and When to Call Your Doctor

Somatropin is a well-studied medication with a long safety record, but like all medications — especially biologic drugs — it carries both common and serious potential side effects. Knowing what to expect can help you and your family distinguish normal treatment responses from warning signs that require immediate attention.

This guide covers the full side effect profile of somatropin — from routine injection site reactions to rare but serious complications — with clear guidance on when to call your doctor.

Common Side Effects of Somatropin

These side effects occur in a meaningful proportion of patients and are generally manageable:

Injection site reactions: Pain, redness, swelling, itching, or bruising at the injection site. These are the most common side effects. Rotating injection sites (stomach, upper arm, thigh, buttock) helps reduce this. Avoid injecting in the same spot each time — this can cause lipoatrophy (fat loss under the skin).

Fluid retention (edema): Adults in particular may experience swelling in the hands and feet, especially at the start of therapy. This is usually dose-dependent and resolves with dose adjustment.

Joint and muscle pain: Arthralgia (joint pain) and myalgia (muscle aches) are common, particularly in adults starting therapy. Usually transient and resolves with dose adjustment.

Carpal tunnel syndrome: Numbness or tingling in the hands, related to fluid retention pressing on the median nerve. More common in adults on somatropin.

Headache: Mild headaches are reported, especially early in treatment.

Serious Side Effects — When to Call Your Doctor Right Away

These are less common but require prompt medical attention:

Intracranial hypertension (increased pressure in the skull): Symptoms include severe headaches, vision changes, nausea, vomiting, or pain behind the eyes. This usually occurs within the first 8 weeks of treatment. Stop somatropin and call your doctor immediately if these symptoms occur.

New-onset diabetes or high blood sugar: Somatropin can reduce insulin sensitivity. Watch for excessive thirst, frequent urination, blurred vision, or unexplained fatigue. Report these to your doctor.

Slipped capital femoral epiphysis (SCFE) in children: A hip condition that can occur in children experiencing rapid growth. Signs include a limp or hip, knee, or leg pain. Call your child's doctor right away if any of these develop.

Scoliosis progression in children: Rapid growth can worsen pre-existing scoliosis. Your child's doctor should monitor for this regularly.

Hypoadrenalism: Somatropin can unmask low cortisol levels. Signs include extreme fatigue, weakness, dizziness, and changes in skin color. Tell your doctor immediately.

New or worsening cancer: Somatropin may increase the risk of developing cancer, particularly in patients who previously received radiation to the head or brain. Regular monitoring for new or recurrent malignancy is recommended.

Boxed Warning: Risk in Prader-Willi Syndrome

Somatropin carries an important warning for pediatric patients with Prader-Willi syndrome (PWS). Sudden death has been reported in PWS patients who were severely obese, had a history of upper airway obstruction or sleep apnea, or had unidentified respiratory infections. These patients should be evaluated for upper airway obstruction and sleep apnea before starting therapy, and somatropin is contraindicated in severely obese PWS patients or those with severe respiratory impairment.

Monitoring While on Somatropin

Regular monitoring is essential during somatropin therapy. Your doctor will likely check:

IGF-1 levels every 4–8 weeks when starting, then every 6 months when stable

Blood glucose/HbA1c — especially if there are diabetes risk factors

Thyroid function tests

Growth velocity in children (height measured every 3–6 months)

Annual fundoscopic exam (to check for intracranial hypertension)

Also read: somatropin drug interactions: what to avoid and what is somatropin: uses and dosage.