Taking your medication too late (or too early) can be as bad as missing doses completely, and can allow HIV to become resistant to some or all of the drugs you are taking.
The safest approach is to aim to take all your medicines at the right time and in the right way. But, being honest, there are bound to be times when you take your medicine late. As long as this happens very occasionally, it shouldn’t make any difference to the success of your treatment. However, regularly taking your medication too late or too early will give HIV an opportunity to become resistant.
Not all anti-HIV drugs are processed by the body at the same rate. Protease inhibitors, particularly those that aren’t boosted by a small dose of ritonavir (nelfinavir and indinavir, neither drug is very widely used now), are metabolised very rapidly, meaning that it’s particularly important to take them correctly.
Other drugs, for example non-nucleoside reverse transcriptase inhibitors (NNRTIs), are more 'forgiving' and it’s not quite so important to take them at very strict intervals - taking them an hour or so late shouldn’t make too much of a difference.
Don’t assume that just because somebody else has taken their anti-HIV drugs constantly late and still has an undetectable viral load, that this will be the case for you, even if they are taking the same drugs as you. The speed and efficiency with which individuals process medicines can vary a lot.
If the way you live your life means that you find it very hard to stick to strict dosing schedules, then talk to your doctor about the possibility of switching to a more ‘forgiving’ combination.
Should you forget to take a dose of your drugs, take it as soon as you remember, and then carry on with your normal dosing schedule. Don’t take a double dose to make up for the one you missed.
You might find that breaking your routine in some way increases the chances that you forget to take your pills on time. If you know that your normal dosing schedule is going to be disrupted, then try and make a plan that ensures you take your medication properly. If you do forget to take your dose, don’t beat yourself up, but try and learn from it so it doesn’t happen again.