L5 Epidural Steroid Injection Side Effects and Risks

Most people who receive an L5 epidural steroid injection experience only mild, short-lived side effects such as temporary soreness at the injection site, facial flushing, or a brief spike in pain. Serious complications are rare but real, and they range from blood sugar disruption and headaches to, in uncommon cases, infection or nerve injury. Because L5 is one of the most frequently targeted spinal levels for these injections, understanding what can go wrong and how likely each problem actually is can help you make a more informed decision before the needle goes in.

Flushing, Sleep Disruption, and Other Steroid-Related Reactions

One of the most common side effects has nothing to do with the needle itself. The steroid medication enters the epidural space and is gradually absorbed into the bloodstream, which can trigger a systemic response. Facial or upper-body flushing is reported by roughly 11 to 28 percent of patients, depending on the steroid used and the injection approach. In one study of interlaminar lumbar injections using dexamethasone, flushing occurred in about 28 percent of cases, was more common in women, and resolved within 48 hours in everyone who experienced it.¹ A separate study using betamethasone and methylprednisolone found a lower overall flushing rate of about 11 percent.² It feels like a warm flush or redness in the face and chest, sometimes mistaken for an allergic reaction, but it is a pharmacological response to the steroid rather than a true allergy.

Other systemic steroid effects include difficulty sleeping, mild mood changes, and a temporary increase in appetite. A large multi-institutional study of over 16,000 epidural steroid injections found that central steroid responses like sleeplessness, flushing, and nonpositional headache occurred in about 2.6 percent of patients, regardless of the injection technique used.³ About 2 percent reported a brief worsening of their pain after the procedure before things improved. These reactions are annoying but not dangerous, and they tend to fade within a few days.

Blood Sugar Spikes if You Have Diabetes

If you have diabetes, this is the side effect to take seriously. Corticosteroids are powerful anti-inflammatory drugs, but they also push blood sugar upward by promoting glucose release and reducing insulin sensitivity. A study tracking 30 diabetic patients found that average blood glucose jumped from about 160 mg/dL before the injection to roughly 286 mg/dL afterward, an increase of around 126 mg/dL. The good news: the spike had a half-life of about one day, meaning glucose levels returned to within the patient’s normal range within approximately two days.⁴ A separate study confirmed that blood glucose was significantly elevated on day one after injection but had normalized by day two.⁵

For people with well-controlled diabetes, this transient spike is usually manageable with closer monitoring and temporary medication adjustments. For those whose diabetes is already poorly controlled, the surge can be more dangerous. If you are diabetic and scheduled for an L5 epidural steroid injection, discuss a glucose management plan with your prescribing physician ahead of time. You may need to check your blood sugar more frequently for the first 48 hours after the procedure.

Blood Pressure Changes

Epidural steroids can also nudge blood pressure upward, though the effect is modest. One study tracking both diabetic and non-diabetic patients found that average systolic blood pressure rose from about 123 mmHg at baseline to around 128 mmHg one week after the injection, then returned to baseline by about three weeks out.⁶ A five-point rise in systolic pressure is not dramatic for most people, but if you have uncontrolled hypertension or a history of cardiovascular events, it is worth flagging with your doctor so your blood pressure can be monitored after the injection.

Post-Dural Puncture Headache

The epidural space sits just outside the dura, the membrane that contains spinal fluid. The needle is supposed to stop in that space. Occasionally, it goes a fraction of a millimeter too far and pierces the dura, creating a small leak of cerebrospinal fluid. The result is a distinctive headache that gets worse when you sit or stand up and improves when you lie flat. This post-dural puncture headache can appear up to five days after the procedure.⁷

Dural puncture during epidural steroid injection is uncommon. In the multi-institutional study of over 16,000 procedures, it occurred in about 0.06 percent of all injections, though the rate was slightly higher with the interlaminar approach (about 0.2 percent) compared to the transforaminal approach (about 0.04 percent).⁸ Most post-dural puncture headaches resolve on their own within a week with rest, hydration, and caffeine. Persistent cases may require a blood patch, where a small amount of your own blood is injected into the epidural space to seal the leak. Rare but more serious consequences of inadvertent dural puncture include intracranial hypotension, subdural hematomas, and cranial nerve palsies.⁹

Infection Risks

Epidural abscess after a steroid injection is rare, but it is one of the complications that keeps pain specialists vigilant about sterile technique. When it does occur, the most commonly identified organism is Staphylococcus aureus. A case series review found that lumbar procedures accounted for most reported epidural abscesses, with L4-L5 being the most commonly affected level. The average time from the injection to symptom onset was about eight days, and definitive diagnosis took an average of 25 days, highlighting how the condition can develop insidiously.¹⁰ Immunocompromised patients appear to be at higher risk. In one literature review, eight of 14 patients with epidural abscess or meningitis following epidural corticosteroid injections were immunocompromised.¹¹

Watch for fever, worsening back pain (especially if it changes character or spreads), or new neurological symptoms such as weakness or numbness in the days and weeks after the injection. These symptoms warrant urgent medical evaluation. The risk of infection is very low when proper aseptic technique is followed, but it is never zero.

Serious Neurological Complications

The most feared, and thankfully rarest, complications involve direct injury to nerves or blood vessels supplying the spinal cord. At the L5 level, the spinal cord itself has already ended (it terminates higher up, usually around L1-L2), so the needle is working around nerve roots of the cauda equina rather than the cord itself. That anatomy offers a degree of protection, but not complete immunity from harm.

The transforaminal approach carries a unique vascular risk because the needle passes close to segmental arteries that may supply the spinal cord. If steroid particles enter one of these arteries, they can block blood flow and cause spinal cord infarction. A case report documented this scenario when a lumbar transforaminal injection occluded a segmental artery that fed the artery of Adamkiewicz, a critical blood vessel for the lower spinal cord.¹² This is an exceptionally rare event, but it is the primary reason many proceduralists now prefer non-particulate steroids like dexamethasone for transforaminal injections. Particulate steroids such as methylprednisolone or triamcinolone have larger particles that can clump and occlude small arteries, while non-particulate formulations are less likely to cause vessel blockage.¹³

A multi-society consensus effort produced 17 clinical recommendations aimed at preventing catastrophic neurological injuries during epidural steroid injections. These include using fluoroscopic or CT guidance, injecting contrast dye before delivering steroid to confirm correct needle placement, and choosing appropriate steroid formulations based on the injection approach.¹⁴

How the Injection Approach Affects Your Risk Profile

Not all epidural steroid injections are performed the same way, and the approach your doctor chooses changes which side effects are more or less likely. Three main techniques exist for the lumbar spine: interlaminar, transforaminal, and caudal. The transforaminal approach delivers medication directly to the affected nerve root but carries higher risk of vascular complications, as described above. The interlaminar approach enters from the back of the spine and spreads medication more broadly but has a higher rate of accidental dural puncture. The caudal approach enters through the sacral hiatus at the base of the spine and is considered the safest trajectory, though it delivers medication less precisely.¹⁵

In practice, the large multi-institutional study found that both transforaminal and interlaminar approaches had low overall adverse event rates, with no major neurological injuries or hemorrhages in over 16,000 consecutive procedures. Vasovagal reactions (feeling lightheaded or faint) were slightly more common with the transforaminal technique at 1.3 percent versus 0.5 percent for interlaminar.¹⁶ The researchers concluded that the choice between approaches should be driven by effectiveness for your specific condition rather than safety concerns alone.

Image guidance matters regardless of the approach. Contrast dye is injected before the steroid to verify the needle is in the right place and to rule out intravascular spread.¹⁷ If your injection is being done without fluoroscopy or CT guidance, that is a red flag worth asking about.

Particulate Versus Non-Particulate Steroids

The steroid formulation your doctor uses influences both the risk profile and the duration of pain relief. Particulate steroids like methylprednisolone and triamcinolone tend to linger at the injection site longer, potentially providing more sustained anti-inflammatory effects. Non-particulate steroids like dexamethasone dissolve in solution, making them safer from a vascular standpoint but possibly shorter-acting. A head-to-head comparison of lumbar epidural dexamethasone versus methylprednisolone found that dexamethasone was close in effectiveness, though there was a trend toward slightly less pain relief and shorter duration that did not reach statistical significance.¹⁸

For transforaminal injections specifically, many guidelines now recommend non-particulate steroids because of the vascular risk. For interlaminar or caudal approaches, where the needle is farther from critical arteries, particulate steroids are still commonly used. Ask your provider which formulation they plan to use and why.

Bone Density Concerns With Repeated Injections

A single injection is unlikely to affect your bones. But epidural steroid injections are often repeated over months or years, and cumulative steroid exposure can reduce bone mineral density. A systematic review found that epidural steroids were associated with decreased bone density in four of six included studies, with significant reductions linked to cumulative methylprednisolone-equivalent doses of 200 mg or more over one year. The risk of osteopenia and osteoporosis was lower in patients who were simultaneously taking anti-osteoporotic medication.¹⁹

Postmenopausal women appear particularly vulnerable. A study of postmenopausal women with low back pain found that those who had received multiple injections, around 14 on average with a cumulative triamcinolone dose of roughly 400 mg, showed lower bone density in the femoral neck and total femur compared to those who had not received repeated injections.²⁰ If you are receiving multiple injections per year, especially over several years, it is reasonable to discuss bone density monitoring with your doctor.

Hormonal Suppression After Multiple Injections

Your adrenal glands produce cortisol in response to signals from the brain. When you receive exogenous corticosteroids, that feedback loop can become suppressed, leaving your body temporarily unable to mount a normal cortisol response to stress. One study compared spine surgery patients who had received multiple epidural steroid injections before their operation to those who had not. The pre-injection group had lower baseline cortisol levels and failed to mount the normal cortisol surge that the body produces in response to surgical stress.²¹ In rare cases, repeated injections have triggered full-blown iatrogenic Cushing’s syndrome, with symptoms including weight gain, a round face, thinning skin, and persistent adrenal suppression.²²

This is mainly a concern for people getting frequent injections. A single injection at L5 is unlikely to meaningfully suppress your adrenal axis. But if you have had several injections over a short period and you are facing surgery, your surgical team should be made aware so they can plan appropriate steroid coverage during and after the procedure.

Allergic and Hypersensitivity Reactions

True anaphylaxis during an epidural steroid injection is exceptionally rare, but it has been documented. The reaction can be triggered by the steroid compound itself or by the iodinated contrast dye used to verify needle placement. One case report described anaphylaxis to a component of the steroid medication during a caudal epidural injection.²³ Another documented a delayed hypersensitivity reaction to iohexol contrast dye, with a skin rash developing seven days after the injection.²⁴

If you have a known allergy to contrast dye, inform your provider before the procedure. Many clinics will premedicate you with antihistamines and steroids, switch to a non-ionic contrast agent, or use an alternative guidance method. If you have previously tolerated epidural steroid injections without problems, the risk of a new allergic reaction on a subsequent injection is extremely low but not zero.

Epidural Lipomatosis

Corticosteroids promote fat deposition, and repeated epidural injections can cause fat to accumulate in the epidural space itself, a condition called epidural lipomatosis. The concern is that excessive epidural fat can compress the neural structures you were trying to decompress with the injection in the first place. A case series found that the odds of developing epidural lipomatosis rose steeply with the number of injections: about 60 percent after two, about 90 percent after three, and approaching 100 percent with further injections, independent of body mass index.²⁵ Those numbers come from a small case series, so the true population rates are uncertain. A retrospective study found a much more modest rate of lipomatosis grade change, about 7.5 percent, after lumbar epidural steroid injection.²⁶ A comprehensive review concluded that while an association between epidural steroid injections and lipomatosis exists in the literature, high-quality evidence proving an independent causal link is still lacking.²⁷

Psychiatric Side Effects

Steroid-induced mood changes usually amount to feeling a little wired or irritable for a day or two. But in rare cases, the effect can be far more dramatic. A case report described an elderly woman with no prior psychiatric history who developed full-blown mania and psychosis roughly a week after her third epidural steroid injection. She became grandiose, paranoid, verbally aggressive, and unable to sleep. Her psychosis lasted nearly a month, and the manic symptoms persisted for about three months before resolving.²⁸

Cases like this are vanishingly rare, but they underscore an underappreciated point: corticosteroids are psychoactive drugs. People with a personal or family history of bipolar disorder, psychosis, or severe anxiety may want to discuss the risk with both their pain specialist and their mental health provider before proceeding. If you notice substantial mood shifts, racing thoughts, or unusual behavior after an injection, seek medical attention rather than assuming it will pass on its own.

Bleeding Complications

Spinal epidural hematoma is a feared but rare complication that could compress the cauda equina and cause lasting damage. A prospective study of over 1,000 patients receiving more than 1,200 epidural steroid injections found zero spinal hematomas. Blood was observed during needle placement in about 5 percent of cases, classified as a minor hemorrhagic complication with no clinical consequences. The study also found that patients taking NSAIDs, including aspirin, did not have a higher rate of minor bleeding events.²⁹ That said, stronger anticoagulants like warfarin, heparin, and newer direct oral anticoagulants are typically held before the procedure per established guidelines. If you are on blood thinners, your provider will give you specific instructions about when to stop and restart them.