If your blood pressure suddenly rises after always running low, and headaches begin during cancer treatment, it is natural to feel alarmed. Yet a rise in blood pressure is one of the more common changes seen with certain cancer therapies. In particular, anti-angiogenic drugs — which block the new blood vessels a tumor needs to grow — and some targeted therapies can affect how blood vessels regulate themselves and push blood pressure upward. Readings may stay normal for the first cycle or two and then climb later, so feeling reassured because it was fine last time is not a reliable guide.
When blood pressure rises, a heavy or throbbing headache, often at the back of the head, frequently comes with it. A headache alone is not necessarily dangerous, but leaving high blood pressure unmanaged puts steady strain on the body, so simply enduring it as a side effect to be expected is not advisable. Measuring at home each morning and evening under the same conditions — seated, after five minutes of rest, with the arm at heart level — and writing down the date, time, and reading gives your care team valuable information.
Sometimes the clinic will lower blood pressure with an injection but not send you home with a prescription. This is usually because starting a daily blood pressure medicine has to be weighed against your chemotherapy schedule, kidney function, and interactions with your other drugs. If there is a gap before your next appointment, it is quite reasonable to visit a nearby internal medicine or primary care clinic, show them the name of the chemotherapy you are receiving and your recent home readings, and discuss a temporary blood pressure medication. Telling them you are on chemotherapy and listing every medicine you take helps them choose something appropriate.
Some situations, however, call for the emergency room rather than waiting for the next visit: very high blood pressure (for example, a top number above 180) together with a severe headache, blurred vision, slurred speech, chest pain or breathlessness, relentless vomiting, or confusion. Rarely, a rapid surge in blood pressure can strain the brain, so any new neurological symptom is worth acting on without delay.
This article is general information and does not replace your own diagnosis or treatment. Whether to start or adjust blood pressure medication, and when to go to the emergency room, should always be decided together with your treating team or a nearby medical provider.