How Do You Know if You Did an Intramuscular Injection Wrong?

October 8, 2025 •

4 min read

According to a study published on PubMed, intramuscular injection errors can lead to serious complications, including nerve injury and muscle contractures. This makes it essential for both practitioners and patients to recognize the signs of a improperly administered shot, answering the critical question: how do you know if you did an intramuscular injection wrong?

Quick Summary

An incorrect intramuscular injection can be identified by severe or prolonged pain, significant swelling, neurological symptoms like tingling, or signs of infection such as fever and redness. Improper technique can lead to nerve or blood vessel damage, altered drug absorption, and local tissue reactions requiring immediate attention.

Key Points

Severe Pain or Neurological Symptoms: Sharp, shooting pain or tingling/numbness during or after an injection can signal a nerve injury.
Prolonged or Excessive Swelling: While some swelling is normal, a large, firm, or growing lump could indicate a hematoma or abscess.
Signs of Infection: Increasing redness, warmth, and pain, possibly with pus, suggest a skin infection like cellulitis.
Visible Blood During Aspiration: Seeing blood in the syringe during aspiration means the needle is in a blood vessel and must be withdrawn and re-injected at a new site.
Ineffective Drug Absorption: If the medication is injected into fat instead of muscle, absorption may be slower, potentially affecting its efficacy.
Allergic Reaction: Anaphylaxis is a rare but serious complication, indicated by symptoms like difficulty breathing, hives, or facial swelling.

Signs of an Incorrect Intramuscular Injection

While some mild soreness and redness are normal after an intramuscular (IM) injection, certain symptoms signal that something went wrong. Recognizing these signs promptly is key to preventing serious complications.

Pain and Discomfort

One of the most immediate indicators of an improper injection is unusual pain. While a momentary sting is expected, you should be concerned if you experience:

Severe, sharp, or shooting pain: This can occur immediately upon injection and may signal that a nerve has been struck. The pain may radiate down the limb, feeling like an electric shock.
Prolonged pain: Normal soreness at the injection site should subside within 24 to 48 hours. If severe pain persists beyond this period, it could indicate a deeper problem.

Swelling, Redness, and Warmth

Some local inflammation is a normal immune response. However, look out for these signs of a serious problem:

Excessive swelling: Swelling that is beyond a minor lump and is firm or getting larger could indicate a hematoma (a collection of blood) or, in rare cases, an abscess.
Spreading redness and warmth: Red streaks extending from the injection site, accompanied by increasing warmth, can be a sign of cellulitis, a bacterial skin infection.
Pus or drainage: Any clear fluid or pus draining from the injection site should be considered a sign of infection and requires immediate medical attention.

Neurological Symptoms

If a nerve is hit, symptoms will likely appear quickly and may be severe. These can include:

Tingling or numbness: A 'pins and needles' sensation or loss of feeling in the limb is a classic sign of nerve irritation or damage.
Weakness or paralysis: An injury to a motor nerve can cause weakness or an inability to move the injected limb. For example, a severe sciatic nerve injury can cause a foot drop.

Allergic Reactions

Although rare, a severe allergic reaction (anaphylaxis) can occur, especially if the person has a pre-existing allergy to the medication. These symptoms can be life-threatening and require emergency medical care.

Sudden rash or hives
Trouble breathing or wheezing
Swelling of the face, lips, or tongue
Rapid heartbeat

Common Errors Leading to Improper Injections

Several technique-related mistakes can cause the complications mentioned above. Understanding these errors can help prevent future issues.

Incorrect Site Selection

Choosing the wrong location for an IM injection is a major cause of complications. Different body sites have different associated risks.

Gluteal area: The dorsogluteal site (upper outer quadrant of the buttock) has a risk of hitting the sciatic nerve if not properly located, potentially causing severe and lasting nerve damage. The ventrogluteal site is generally considered safer.
Deltoid muscle: Incorrectly placing the injection too high in the deltoid can lead to shoulder injury (SIRVA), which causes chronic pain and limited range of motion.

Incorrect Needle Depth or Angle

The needle must be long enough to reach deep into the muscle tissue for proper absorption. Using a needle that is too short, or not inserting it fully, can lead to the medication being delivered into the subcutaneous fat layer instead of the muscle.

Impact: This can result in slower, less effective absorption of the medication. With some drugs, it may also increase local pain and swelling.
Technique: The needle should be inserted at a 90-degree angle for IM injections. Using an incorrect angle can increase the chance of hitting subcutaneous tissue or other structures.

Hitting a Blood Vessel

Before injection, a common practice called aspiration involves pulling back slightly on the plunger to check for blood. If blood appears, the needle is in a blood vessel and must be withdrawn and a new site selected. Failure to do this can cause issues.

Hematoma: If a blood vessel is broken, it can lead to internal bleeding and a painful hematoma.
Vascular occlusion: Injecting certain oil-based medications directly into the bloodstream can be dangerous, causing vascular occlusion.

Comparing Proper vs. Improper Injection Outcomes


Feature	Proper Intramuscular Injection	Improper Intramuscular Injection
Initial Sensation	Mild, temporary stinging sensation.	Sharp, radiating, or intense electric-shock like pain.
Post-Injection Pain	Mild soreness lasting 1-2 days.	Severe or prolonged pain (>48 hours).
Local Swelling	Minor lump or mild, transient swelling.	Excessive, firm, or spreading swelling.
Absorption Rate	Fast and reliable drug absorption.	Slow or erratic, potentially impacting drug efficacy.
Neurological Symptoms	None.	Tingling, numbness, weakness, or paralysis.
Serious Complications	Very rare.	Abscess, cellulitis, hematoma, or nerve damage.

What to Do If You Suspect an Incorrect Injection

Do not ignore the symptoms: If you experience any of the severe signs mentioned, especially sharp pain, radiating numbness, or signs of infection like fever and excessive redness, do not wait.
Contact a healthcare professional: Call your doctor or seek prompt medical care. Be prepared to describe your symptoms, where you received the injection, and what medication was given.
Do not re-inject: If you suspect the injection failed, do not attempt to re-administer the dose. In some cases, repeating a vaccine dose is recommended, but only under a healthcare provider's guidance.
Report the error: In some healthcare settings, particularly for vaccines, reporting administration errors to systems like VAERS (Vaccine Adverse Event Reporting System) is required. This helps track adverse events and improve safety protocols.

Conclusion

Recognizing the signs of an improperly administered intramuscular injection is crucial for managing potential complications. While mild side effects are common and resolve quickly, severe or persistent pain, neurological symptoms, and signs of infection indicate a problem that requires immediate medical attention. By being vigilant about post-injection symptoms and understanding the risks associated with incorrect technique, you can ensure a safer outcome. Always consult a healthcare professional if you are concerned about an injection, as prompt intervention can prevent more serious issues. For further information on injection techniques, reliable resources like MedlinePlus offer detailed instructions and guidance on proper administration.

Frequently Asked Questions

Yes, mild pain and soreness at the injection site are normal. This is usually caused by the needle piercing the muscle tissue and the inflammatory response to the medication, and should resolve within 1-2 days.

Normal swelling is typically a minor, temporary lump that resolves quickly. Problematic swelling is excessive, firm, spreading, and may be accompanied by increasing pain or warmth. Seek medical attention if swelling is severe or worsens.

Signs of hitting a nerve include a sudden, sharp, electric-shock-like pain that may radiate down the limb. The affected area may also experience tingling, numbness, or weakness.

Yes, although uncommon, an infection can occur if aseptic technique is not followed. Signs of infection include increasing redness, warmth, pain, and potentially pus or drainage from the site. This requires medical treatment.

If an IM injection is too shallow and goes into the subcutaneous fat instead of the muscle, it can alter the absorption rate of the medication. This may make the medication less effective and cause more local pain and irritation.

If you see blood in the syringe when you pull back the plunger (aspirate), it means you have hit a blood vessel. You should withdraw the needle, dispose of the syringe, and prepare a new dose to be injected at a different site.

Contact a doctor immediately if you experience severe or prolonged pain, excessive swelling or redness, fever, pus, tingling or numbness, or signs of a serious allergic reaction like trouble breathing or hives.