Don't take painkillers on more than 15 days a month, or combination painkillers on more than 10 days, or the headache may be caused by the medicine itself

Moderate value
Evidence B
Buys life
Free
Takes minutes
Some willpower

In plain words

If you have frequent headaches and take painkillers every day, the headaches may get worse the more you take. The international headache classification calls this medication-overuse headache. Taking ordinary painkillers on 15 or more days a month, or combination painkillers on 10 or more days, for more than 3 months in a row, is enough to qualify. Most people improve after stopping the overused drug.

Cost: Free. You have to keep track of the days you take medicine, and resist taking a pill on reflex.
What you get: The International Classification of Headache Disorders, 3rd edition, from the International Headache Society, gives the diagnostic criteria. A person who already has a headache disorder has headaches on 15 or more days a month and has regularly overused headache medicine for more than 3 months. For non-opioid painkillers such as acetaminophen, aspirin and ibuprofen, the threshold for overuse is 15 or more days a month. For combination painkillers, the threshold is 10 or more days a month. Combination painkillers are those that put two or more pain-relieving drugs together, or add a helper ingredient such as caffeine, for example acetaminophen plus codeine. If you rotate several non-opioid painkillers, count the days together. The classification notes that epidemiological evidence from several countries shows that more than half of the people with headaches on 15 or more days a month have this kind of headache. Most patients improve after stopping the overused drug, and treatment to prevent headaches works better as well.
Notes: Painkiller tablets with the character 咖 in the name generally contain caffeine and count as combination painkillers, with the 10-day limit. If the number of headache days in a month keeps rising, see a neurology department, and don't rely only on adding more medicine. Graded B because the classification gives diagnostic thresholds, not a controlled trial. The benefit is rated “medium” as a judgment: what it gets you is fewer headache days, and death is not involved.
Evidence grade: B : Supported by research but without a precise number, or based on small or single studies.
Sources: Headache Classification Committee of the International Headache Society (2018). The International Classification of Headache Disorders, 3rd edition. Cephalalgia, 38(1):1-211. https://doi.org/10.1177/0333102417738202
ICHD-3 在线版 8.2 Medication-overuse headache（含 8.2.3、8.2.5）. https://ichd-3.org/8-headache-attributed-to-a-substance-or-its-withdrawal/8-2-medication-overuse-headache-moh/

Mentioned in

For period pain, take a painkiller such as ibuprofen rather than toughing it out; if the pain keeps you from work or school, or three months of medicine doesn't control it, see a gynecologist

Translated from the Chinese original. Original book, section 34, tip 9. This section is about health and medicines. It is general information, not a substitute for a doctor’s diagnosis or prescription. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer