Antibiotics: What Happens If You Take Them Late or Expired? 7 Questions Answered

Is it safe to take an antibiotic late or expired? We answer 7 key questions about how to use them, their risks, and resistance. Avoid common mistakes.

[This text has been written by Marina Tarrús, Victoria Ballén, Natalia Rosón and Sara Soto.]

It is important to be very careful with antibiotics: not to harm our health and not to contribute to their decreasing effectiveness.

1. Can I take an antibiotic when I think I need it, even if it has not been prescribed by a doctor?

No, you should only take antibiotics when the treatment has been prescribed by a physician because only they have the necessary expertise in infections and how to treat them with antibiotics. Your doctor will first identify what kind of infection you have (whether it is caused by a virus or a bacteria, for example) and then prescribe the appropriate treatment. Remember that antibiotics are only effective against bacterial infections. Protocols have been developed to assist medical personnel in making a diagnosis. These are made available through regional, national and international health networks, such as the PROA programme, and are included in guidelines produced by teams of health professionals. Doctors use these protocols to monitor the patient’s condition and symptoms and to decide on the most appropriate treatment in each case. For example, a patient with a mild bacterial infection may be prescribed anti-inflammatory drugs to alleviate their symptoms, thereby avoiding the need for antibiotic treatment. Or the treatment may be modified several times depending on the patient’s immune response.

2. Can I modify the prescribed antibiotic regimen if I am feeling better?

No, under no circumstances should you modify the treatment regimen (by changing the interval between doses for example) or discontinue treatment without specific instructions from your doctor! If you feel better it may be because the antibiotic therapy is working, but you must still complete the whole course of treatment prescribed by your doctor to ensure that all of the bacteria that caused the infection are eliminated and to reduce the chances of developing an infection caused by bacteria that are resistant to the antibiotics you are taking. Furthermore, if you still have symptoms after you complete a course of antibiotics, you should schedule a follow-up consultation with your physician, who will evaluate the situation and, if necessary, adjust the antibiotic regimen.

3. Can I take antibiotics left over from a previous treatment?

No, you should not save leftover doses of an antibiotic once you have completed the prescribed course of treatment. And you should never use leftover antibiotics to self-medicate when you think you have a bacterial infection or pass them on to someone you trust who asks you for the drugs because they think they need them. Only a doctor can evaluate whether a patient needs antibiotic treatment and prescribe the appropriate medication. If the box you receive from the pharmacy contains more antibiotics than you need to complete the prescribed course, once you have completed your treatment you must take the leftover medication back to the pharmacy and deposit it in the white SIGRE drop-off bin (Punto SIGRE). You can dispose of any kind of medication you no longer require in these bins. If you do this, as well as taking care of your own health you will also be taking care of the environment because anything disposed of in SIGRE bins will be properly treated and disposed of as medication, something that does not happen when medications are discarded in a general waste bin. Medication in Spain is currently not supplied in exact individualised quantities, although work is being done to make this possible in the future. So, any antibiotics left over after you have completed the prescribed course are the result of issues related to production or logistics and have nothing to do with the appropriate treatment or the number of doses you should take.

4. Can I take expired antibiotics?

No. Expired antibiotics will not be effective. The expiration date indicates the point at which the drug compounds have deteriorated and lost their potency against the bacterial microorganism. This can be because the active ingredient is no longer effective or because the preservatives in the medication have deteriorated more rapidly due to factors such as fluctuations in temperature, light or humidity. In the worst case scenario, expired antibiotics can become toxic. Whenever you get sick and do not feel better after a few days, you should consult a health professional, who will identify your symptoms and prescribe an appropriate treatment. If you have been prescribed antibiotics and you have the same medication at home which has expired, take the expired drugs to the drop-off bin in your local pharmacy (Punto SIGRE) and buy the medication you have been prescribed. Remember, if there is medication left over after you complete the prescribed course of treatment, you must also deposit this in a SIGRE bin.

5. What should I do if I forget a dose of antibiotics? Can I take two at once? Can I take a dose earlier or later than prescribed?

It is not recommended to change the timing of antibiotic doses, as they are dosed to maintain an optimal concentration in the body, ensuring their effectiveness against the infection. If you take a dose earlier, the concentration could be too high and become toxic. If you delay or skip a dose, the amount of antibiotic in your body will decrease and the bacteria may multiply again. Additionally, being exposed to insufficient doses can lead to antibiotic resistance, making the treatment less effective.

If you have missed a dose, do not take two at once, as the concentration would be twice the expected amount and could be toxic. The best thing to do is take only one as soon as possible and then continue following the correct schedule from the time you took the last dose.

A helpful tip: set an alarm to remind you of each dose.

This advice applies to both oral and topical antibiotics. You should follow the schedule provided by the medical staff and not interrupt the treatment prematurely, even if the symptoms have disappeared, as the infection may not be fully eliminated.

6. Can I mix antibiotics with other medications?

You should always tell your doctor what other medications you are taking because antibiotics can interact with other drugs, for example certain anticoagulants and antacids, and they may even reduce the effectiveness of contraceptive pills.

7. Can I mix antibiotics with alcohol?

In general, when taken in moderate amounts, alcohol does not affect antibiotic therapy. However, there are some exceptions, such as metronidazole, which can cause adverse effects, including tachycardia and hot flushes, when mixed with alcohol.