Codeine does not raise blood pressure. It typically lowers it. As an opioid, codeine causes blood vessels to widen, which reduces pressure in the cardiovascular system. This effect can range from barely noticeable to clinically significant depending on the dose, your overall health, and what other medications you’re taking. There is one important exception: stopping codeine after regular use can temporarily spike blood pressure above normal levels.
How Codeine Affects Blood Pressure
Codeine triggers the release of histamine from specialized immune cells called mast cells. This happens within about 30 minutes of taking a dose. Histamine dilates blood vessels, which is why people taking codeine sometimes experience flushing, skin warming, sweating, and itching. That same vessel-widening effect reduces blood pressure.
The most common blood pressure issue with codeine is something called orthostatic hypotension, a drop in pressure that happens when you stand up from sitting or lying down. This can cause dizziness, lightheadedness, or even fainting. The FDA-approved prescribing information for codeine explicitly warns that it “may produce orthostatic hypotension and syncope in ambulatory patients” and that it “produces peripheral vasodilation which may result in orthostatic hypotension and fainting.” Getting up slowly and lying down when you feel dizzy are the standard ways to manage this.
Who Faces the Greatest Risk
Codeine’s blood pressure-lowering effect is more dangerous in certain situations. If your blood volume is already low from dehydration, blood loss, or illness, codeine can push pressure down to unsafe levels. The same applies if you’re taking other medications that lower blood pressure, such as certain psychiatric drugs or general anesthetics. People in circulatory shock face particular risk because the additional vessel dilation can further reduce the heart’s ability to pump blood effectively.
Elderly patients are especially vulnerable. They’re more likely to have compromised heart, liver, or kidney function, and they’re more sensitive to codeine’s sedating and blood pressure effects. Prescribers are advised to start with the lowest possible dose in older adults for this reason. Anyone with pre-existing low blood pressure should use codeine cautiously, as it can worsen the condition.
Codeine Overdose and Blood Pressure
In overdose, codeine’s pressure-lowering effect becomes severe. The National Institutes of Health lists dangerously low blood pressure and a weak pulse among the cardiovascular signs of codeine overdose. This happens because the drug’s vessel-widening and central nervous system effects are amplified at high doses, sometimes to life-threatening levels.
Withdrawal Can Raise Blood Pressure
Here’s where things reverse. If you’ve been taking codeine regularly and then stop, your nervous system rebounds in the opposite direction. During active opioid use, the body’s “fight or flight” system is suppressed. When the drug is removed, that system becomes hyperactive, driving up blood pressure, heart rate, and other stress responses.
Research measuring this effect found that systolic blood pressure (the top number) jumped by an average of 12 mmHg during opioid withdrawal, rising from about 122 to 134. Heart rate increased by roughly 5 beats per minute, about a 6% rise from baseline. These changes reflect a surge in sympathetic nervous system activity, the same system responsible for other withdrawal symptoms like dilated pupils, sweating, and anxiety.
So while codeine itself lowers blood pressure, the rebound after stopping it can temporarily push pressure higher than your normal baseline. This is one reason why tapering off opioids gradually, rather than stopping abruptly, is the standard approach for people who’ve been using them regularly.
The Bottom Line on Codeine and Blood Pressure
If you’re worried about high blood pressure, codeine is unlikely to make it worse while you’re actively taking it. The real cardiovascular concern with codeine runs in the opposite direction: it can drop your pressure too low, particularly if you’re older, dehydrated, or on other medications that also lower blood pressure. The only scenario where codeine is associated with increased blood pressure is during withdrawal after regular use, when the body overcorrects as it adjusts to functioning without the drug.