HGH Storage, Reconstitution, and Injection: Complete Guide (Powder & Liquid)

For patients prescribed somatropin (HGH). Educational only; always follow your product label and your clinician’s instructions.

Quick summary:

Before mixing: Most lyophilized (powder) HGH should be refrigerated 2–8 °C (36–46 °F) and protected from light.
After mixing: Keep refrigerated; usable window varies by brand and diluent (e.g., ~14 days with bacteriostatic water for some products; shorter with sterile water). Some liquid pens allow limited room-temperature use after first use. Always confirm on your exact label.

What is HGH (Somatropin) and how is it supplied?

HGH (somatropin) is supplied either as:

Lyophilized powder in vials (requires reconstitution before injection), or
Prefilled liquid pens/cartridges (already in solution, used with a pen device).

Brand handling and stability rules differ (e.g., Genotropin, Omnitrope, Humatrope, Norditropin). Always default to the instructions that came with your specific product.

Storage — Before Reconstitution (Powder Vials)

Temperature: Store in a refrigerator (2–8 °C / 36–46 °F) unless your label explicitly allows otherwise.
Light / handling: Keep in original carton, protect from light; do not freeze.
Travel: Use an insulated pouch/cold pack; avoid heat spikes.

Some labels allow limited room-temperature periods before mixing; this is brand-specific. Follow your exact insert.

Reconstitution (Mixing) — Powder Vials

What you’ll typically need

Your HGH vial (powder)
Diluent: usually Bacteriostatic Water for Injection (0.9% benzyl alcohol) for multi-dose use; some kits include Sterile Water for Injection (single-use, much shorter shelf life)
Alcohol swabs, insulin syringes or mixing device, clean surface

Shelf life after mixing depends heavily on diluent: many labels list ~14 days refrigerated with bacteriostatic water and ~24 hours with sterile water. Confirm on your product’s insert.

Step-by-step (general, brand-agnostic)

Clean & check: Wash hands. Wipe vial stoppers with alcohol; let dry.
Add diluent slowly: Insert the diluent needle through the stopper and let the diluent run down the side of the vial. Do not shake; this helps prevent foaming/denaturing.
Dissolve gently: Swirl or roll the vial gently until fully dissolved. Solution should be clear and particle-free; if cloudy or with particles, do not use.
Label & store: Mark the date/time mixed and put it immediately in the refrigerator (2–8 °C / 36–46 °F) unless your label specifies otherwise.

Storage — After Reconstitution (Mixed Solution)

Refrigerate at 2–8 °C (36–46 °F). Do not freeze. Protect from light.
Use-by window depends on brand & diluent:
- Humatrope: after mixing, use within 14 days refrigerated (bacteriostatic water). If mixed with sterile water, use within 24 hours.
- Genotropin pen cartridges: discard after 28 days refrigerated between uses.
- Omnitrope cartridges: stable up to 28 days refrigerated after first use. (Vial reconstituted with non-preserved diluent may be 24 hours.)
- Norditropin FlexPro liquid pens: after first use, may be kept at room temperature (≤25 °C/77 °F) for up to 3 weeks, or refrigerated for up to 4 weeks (choose one option). Keep away from light; do not freeze.

If the solution becomes cloudy, develops particles, or has been frozen/overheated, discard it per your label.

Prefilled Liquid Pens / Cartridges (No Reconstitution)

Many brands supply pens with ready-to-use liquid. General themes (verify your label):

Store refrigerated before first use.
After first use, some pens (e.g., Norditropin FlexPro) permit room-temperature storage up to ~3 weeks, or refrigerated up to ~4 weeks; unused pens must remain refrigerated.
Discard any remaining medication after the label’s stated time from first use (e.g., ~28 days for certain Genotropin/Omnitrope cartridges).

How to Inject HGH (Subcutaneous) — General Patient Education

Important: This section is general information for patients who have already been shown how to inject by a clinician. It is not a substitute for live training. Always use the device and technique your product was designed for.

Sites

Common subcutaneous sites: abdomen (at least 2″ from the navel), front/outer thigh, back of upper arm, buttock/hip. Rotate sites to reduce local irritation and lipoatrophy.

Supplies

Pen device (if using a pen) or insulin syringe (e.g., 29–31G), alcohol swabs, sharps container.

Steps (vial/syringe or pen)

Prepare: Wash hands; gather supplies. Check that solution is clear and in date.
Clean: Wipe the rubber stopper (vial) and the skin at the injection site with alcohol; let dry.
Draw / dial dose:
- Vial & syringe: Inject air into the vial (equal to dose), invert, draw dose slowly. Tap out bubbles; do not shake the vial.
- Pen: Attach a new needle, prime if required, dial the prescribed dose per device instructions.
Inject: Pinch a fold of skin. Insert the needle at 90° (or per clinician’s advice), inject slowly, then wait a few seconds before withdrawing.
Dispose: Do not recap. Place needle in an approved sharps container.
Store: Return the medication to refrigeration (or room temp if your pen allows it per label). Keep away from light.

If you hit blood, see unusual redness/swelling, or the solution looks wrong, stop and contact your prescriber or pharmacist.

Bacteriostatic vs Sterile Water — What’s the difference?

Bacteriostatic Water (with benzyl alcohol): Intended for multi-dose use; many labels allow longer in-fridge use (often ~14 days).
Sterile Water (no preservative): Single-use only; mixed solution typically must be used within 24 hours and kept refrigerated.

Always use the exact diluent specified for your product and device.

Common Mistakes to Avoid

Shaking the vial/pen (can denature protein).
Storing outside the label’s temperature/time limits (e.g., forgetting a pen in a hot car).
Reusing needles or failing to rotate sites.
Mixing with the wrong diluent or using tap water.
Keeping mixed solution past its allowed time (14–28 days for some preserved products; often ≤24 hours with sterile water).

FAQ

Can I keep lyophilized HGH at room temp before mixing?
Sometimes, but only if your label allows it and usually for limited time; refrigeration is the default safest choice.

My pen says I can store at room temperature after first use — really?
Some brands (e.g., Norditropin FlexPro) permit room temp (≤25 °C/77 °F) for up to ~3 weeks after first use, or refrigerated up to ~4 weeks. Follow your device’s insert exactly.

How long is mixed HGH good for?
Depends on brand & diluent: e.g., Humatrope ~14 days refrigerated with bacteriostatic water; Genotropin/Omnitrope cartridges commonly 28 days refrigerated; Sterile water mixes may be ~24 hours. Check your label.

Safety & Legal

This content is educational and not medical advice. HGH is a prescription medicine; use only under medical supervision and exactly as labeled for your product and device. Storage/injection rules vary by brand; your label and clinician’s directions override this guide. Dispose of sharps properly and follow local regulations.