Reconstitution & Dosage Calculator

• Amount of Substance: Enter the amount of active substance in the vial. Select the unit (mg or µg).

• Solution Volume: Enter the volume of liquid provided for reconstitution in the vial. (in ml).

• Desired Dose: Enter the desired dose. Select the unit (mg, µg or Units).

• Convert to Units (optional): If you want to calculate the dose in Units, check the box and enter the concentration of the solution in Units per 1 ml.
  Note: If you select "Units" for Desired Dose, you must enter the Units per ml here. The Amount of Substance and Solution Volume fields will then be disabled, as they are not required in this case.

• Calculate: Click "Calculate" to determine the required volume.

• Results: The result shows the required volume in ml. Depending on your selection, the dose in Units will also be displayed.

• Check: Always recalculate the result yourself and do not change any medication before consulting your doctor.

Practical Example

For example, if you reconstitute a vial containing 3 mg of powder with 1 ml of the provided diluent and you need a dose of 0.25 mg, drawing 0.25 ml with the syringe would be incorrect and could lead to an overdose. The correct amount to draw in this case is 0.083 ml. The calculator helps you determine the exact amount safely.

This tool is for informational and educational purposes only and does not replace professional medical advice, diagnosis, or treatment. Always read the package insert and consult a doctor or pharmacist if in doubt. Incorrect dosing can pose health risks.

Guide for a Typical Reconstitution

If you don't have prefilled pens for the medication your doctor prescribed and need to reconstitute the vial the old-school way, it's best to have your doctor show you exactly how to do it. As a little reminder, I've put together a short guide for you.

• Preparation

  • Thoroughly clean your workspace.

  • Wash or disinfect your hands carefully.

  • Gather all necessary materials and disinfect them. This includes the vial with powder, the solvent ampoule, a sterile syringe and needle, disposable medical gloves, disinfectant, alcohol swabs, and a pad to safely break the ampoule.

• Preparing the Syringe with Needle

  • Take the syringe out of its packaging.

  • Take the needle out of its packaging, but leave the protective cap on.

  • Carefully attach the needle straight onto the syringe tip.

  • Press the needle firmly until it is securely in place.

  • Keep the protective cap on the needle until you are ready to use it to maintain sterility.

• Drawing the Solvent from the Ampoule

  • Disinfect the ampoule with an alcohol swab.

  • Protect the ampoule neck at the marked break point with a pad.

  • Break the ampoule away from the marked point.

  • Remove the protective cap from the prepared needle.

  • Insert the syringe carefully into the ampoule while keeping it vertical or slightly tilted.

  • Slowly pull back the plunger to draw up the entire liquid.

  • If air bubbles are present, hold the syringe upright and gently tap it so the bubbles rise.

  • Push the plunger slightly to remove all air bubbles so only the solution remains in the syringe.

  • Check the amount and adjust if necessary.

• Adding the Solvent to the Vial

  • Remove the aluminum cap from the vial to expose the rubber stopper.

  • Disinfect the rubber stopper with an alcohol swab.

  • Remove the protective cap from the needle and slowly insert the solution straight through the rubber stopper into the vial.

  • Hold the vial slightly tilted and let the solution run gently against the inside wall of the glass. This prevents the solution from hitting the powder directly, which could cause foaming or clumping.

  • Carefully withdraw the needle.

  • Gently roll or tilt the vial (do not shake), until the powder is fully dissolved.

• Aftercare

  • Dispose of used syringes, needles and ampoules safely in an approved container.

  • Many substances need to be stored in the refrigerator. The final solution is stable for a few days up to several months depending on the substance. Check the package insert or consult your doctor for specific information. It is advisable to wait at least two hours before first use to ensure a complete and uniform solution.

Correct Injection Angles

As mentioned before, all of this information should always be discussed thoroughly with a medical professional. The following overview is only a small reminder and shows the most important types of injections, their typical angles, and suitable needles.

• Intramuscular Injections
  With this method, the medication is injected deep into a skeletal muscle. Typical injection sites include the deltoid muscle in the upper arm, the gluteal muscles, or the thigh muscle. Intramuscular injection allows for rapid absorption of the active substance into the bloodstream and is often used for vaccines, depot preparations, and medications with larger volumes. The needle is inserted at a 90° angle.
  
  For intramuscular injections, needles typically have a length between 22 and 25 mm and a thickness of approximately 25 to 27 Gauge (= outer diameter Ø 0.5 mm to Ø 0.4 mm). Common injection sites are the deltoid muscle in the upper arm, the lateral thigh muscle (Vastus lateralis), and the hip (ventrogluteal area). During the IM injection procedure, the skin is often stretched or pulled using the Z-Track technique to keep the medication in the muscle and protect soft tissue.
  
  

• Subcutaneous Injections
  These injections are administered into the fatty tissue beneath the skin (subcutis). They are suitable for medications that need to be absorbed slowly and evenly, such as insulin, blood thinners, or allergy medications used in desensitization therapy. The needle is usually inserted at a 45° angle.
  
  For subcutaneous injections, needles are shorter than for IM injections, typically about 12 to 16 mm, to avoid inserting the needle too deeply and to allow slower absorption. The needle thickness is usually between 25 and 30 Gauge (= outer diameter Ø 0.5 mm to Ø 0.3 mm). Many medications for subcutaneous injection (such as insulin) are also available in prefilled pens, which simplify administration.
  
  

• Intravenous Injections
  Here, the medication is injected directly into a vein. This method allows for very rapid action, as the substance enters the bloodstream immediately. It is often used in hospitals during emergencies, or for administering fluids, medications, or nutrients. The needle is inserted at a shallow angle of about 25° to the skin surface.
  
  For intravenous injections, specialized cannulas or thinner needles are commonly used to establish venous access safely and as painlessly as possible. The choice of needle gauge and length depends on the vein size and the type of infusion, typically ranging from 20 to 24 Gauge (= outer diameter Ø 0.9 mm to Ø 0.6 mm).
  
  

• Intradermal Injections
  Intradermal injections are given into the middle layer of the skin (the dermis), just beneath the epidermis. This technique is mainly used for allergy tests or tuberculosis screenings. The needle is inserted very shallowly at an angle of 10–15°, and a small bleb (wheal) forms at the injection site.
  
  Intradermal injections require very short needles, often around 8 mm in length, since only the uppermost skin layer needs to be reached. The typical needle thickness is 25 to 27 Gauge (= outer diameter Ø 0.5 mm to Ø 0.4 mm), allowing precise administration without penetrating too deeply.