Finasteride is a medication prescribed to manage androgenetic alopecia, commonly known as male pattern baldness. It functions by targeting the core hormonal driver of this condition, dihydrotestosterone (DHT). The drug inhibits the 5-alpha reductase enzyme, which converts testosterone into DHT. Because consistent daily use is necessary to maintain the therapeutic effect, patients often become concerned about missing a single day of treatment.
The Immediate Impact of Missing One Dose
Missing one dose of finasteride (typically the 1-milligram tablet) is unlikely to have any measurable impact on the overall effectiveness of the treatment. The therapeutic benefit does not rely on a constant, moment-to-moment presence of the drug in the bloodstream. Instead, the drug works by initiating a sustained biological action. A single dose lowers the level of DHT in the serum by approximately 65% within the first 24 hours. This substantial suppression is not instantly reversed by a 24-hour gap, and the body’s DHT concentration remains significantly suppressed.
Understanding the Drug’s Activity Window
The reason a single missed dose is not concerning lies in how finasteride interacts with the 5-alpha reductase enzyme. While the drug’s half-life in the blood is relatively short (about five to six hours), this does not reflect the duration of its biological action. Finasteride forms a stable complex with the Type II 5-alpha reductase enzyme, effectively disabling it from converting testosterone to DHT. The body clears this drug-enzyme complex extremely slowly, with a reported half-life of approximately 30 days. The enzyme’s function remains inhibited until the body synthesizes new enzyme molecules, creating a sustained suppression of DHT that extends far beyond the time the drug is detectable in the plasma.
What to Do After Missing a Dose
If you realize you have missed a dose, the primary instruction is to simply resume your regular schedule when the next dose is due. You should not take two tablets on the same day to make up for the one you skipped. Doubling the dose provides no additional benefit because the 5-alpha reductase enzyme is already maximally inhibited at the standard 1-milligram dose. Taking extra medication only increases the concentration of the drug in the blood, slightly elevating the risk of side effects without increasing DHT suppression. If you remember the missed dose within a few hours of the usual time, you can take it, but if it is already closer to the time for your next dose, just skip the missed one entirely and continue with the next scheduled dose.
Consequences of Stopping Finasteride Treatment
The negligible impact of a single missed dose contrasts sharply with the consequences of long-term non-adherence or complete cessation of the medication. Once treatment stops, finasteride molecules are gradually cleared from the body, allowing the 5-alpha reductase enzyme to regain its function. The body’s DHT levels will begin to rise, typically returning to the pre-treatment baseline within about 14 days after the last dose. This return of DHT causes the hair follicles maintained or regrown during treatment to once again begin the miniaturization process. The progressive hair loss that was halted will resume, and the positive effects achieved will slowly reverse over six to twelve months.