A cortisone shot, or corticosteroid injection, is a powerful anti-inflammatory medication that mimics the body’s natural stress hormone, cortisol. While highly effective at reducing pain and inflammation in a targeted area, the medication can be absorbed into the bloodstream. This systemic absorption may temporarily affect other bodily functions, including causing a transient elevation in blood pressure. This recognized side effect is important for all patients, especially those with pre-existing hypertension, to understand.
Defining Corticosteroid Injections
Corticosteroid injections are synthetic drugs designed to suppress the immune response and reduce localized inflammation. The medication is delivered directly to the source of pain, such as a joint, tendon, or bursa, providing focused relief for conditions like arthritis or tendinitis. This targeted approach is generally preferred because it minimizes the widespread side effects associated with oral steroid use.
The risk of blood pressure changes depends on the injection method and the degree of systemic absorption. Localized shots, such as those into a knee joint (intra-articular) or soft tissue, are intended to stay primarily at the injection site. However, even these can lead to some systemic absorption, meaning the medication enters the bloodstream.
More systemic injections, like those given into a large muscle (intramuscular) or the epidural space of the spine, have a greater likelihood of circulating throughout the body. The risk of systemic side effects, including changes in blood pressure, is proportional to the total dose administered and the degree of systemic absorption.
The Mechanism: How Cortisone Affects Blood Pressure
Corticosteroids affect blood pressure due to their structural similarity to adrenal hormones that possess mineralocorticoid activity. These hormones regulate the balance of water and electrolytes, particularly sodium and potassium, in the body. When absorbed systemically, the corticosteroid binds to these receptors, mimicking a state of excess mineralocorticoid action.
This activity stimulates the kidneys to retain more sodium and, subsequently, more water. The retention of water increases the total volume of fluid circulating within the blood vessels. This increased blood volume requires the heart to pump harder, resulting in an elevated blood pressure reading.
The steroid effect can also interact with the renin-angiotensin-aldosterone system (RAAS), a complex hormonal pathway that controls blood pressure. By promoting fluid accumulation, the corticosteroid contributes to a temporary state of fluid overload. While this fluid shift is subtle for many, it can be more pronounced for those with underlying heart or kidney conditions.
Duration and Monitoring
The blood pressure elevation following a cortisone injection is typically a transient effect that resolves on its own. The rise usually begins within a day after the shot and peaks within the first few days. For most patients, elevated readings subside completely within five to seven days as the body metabolizes and clears the medication from the system.
Systemic effects can sometimes last for up to a few weeks, depending on the specific corticosteroid type and dose. Corticosteroids formulated for a longer duration of action at the injection site may also have a prolonged systemic effect. It is advisable to track blood pressure readings at home, starting the day after the injection, to monitor for any significant or sustained increase.
Patients managing high blood pressure should be diligent about self-monitoring, recording readings at least twice daily. Noting the time of the injection and subsequent readings helps the healthcare provider establish a clear timeline. This documentation is important for distinguishing a temporary drug effect from a change in a pre-existing condition.
When to Consult a Healthcare Provider
While a mild, temporary increase in blood pressure may not be cause for immediate alarm, certain readings or symptoms warrant contacting a healthcare provider without delay. Call your doctor if your blood pressure consistently measures above 180/120 mmHg, or if a persistent elevation does not begin to trend downward after the first week.
Symptoms signaling a potentially serious high blood pressure event, known as a hypertensive crisis, require prompt medical evaluation. These warning signs include a severe headache that does not improve with standard pain medication, chest pain, shortness of breath, sudden vision changes, or confusion.
For patients already taking medication for hypertension, the doctor may recommend temporary adjustments to the dosage or type of antihypertensive drug to manage the expected increase. Never stop or change your blood pressure medication without explicit instruction from your healthcare provider. Discussing your cardiovascular history beforehand allows the provider to anticipate the risk and create a proactive monitoring plan.