It's bound to happen no matter how strong your immune system is. Some virus or bacteria manages to worm its way into your body and begins propagating like it's New Year's Eve. Though you may be tempted to ignore it for fear of the guilt that comes with not making a gym date, don't be stupid.
Remember that your body isn't going to just fall back into a mushy pile of fat. That takes as much time as getting ripped. Allow yourself to take off the time you need in order to get better. Fully healing and then hitting the gym will lead to far better gains than if you partially heal, workout and then succumb to the sickness again because you pushed yourself too hard.
Would you rather miss three days or seven?
That's the question it comes down to.
As for recovery, there are simple rules you should follow for those yearly flus and colds we all hate.
You'll no doubt sweat. Even when not sweating, your body needs water to function optimally. Do not deprive yourself of this liquid no matter how gross it feels going down.
Personally, I stock up on vegetable soups that don't have rice or noodles. The veggies are much better than breads (i.e. noodles) at keeping my nutrient levels high. As for sodium levels, go with what you feel comfortable eating. Even a veggie soup can quickly send your sodium levels sky rocketing. If you are worried about that, go with a low sodium option. Just don't skip out on salt altogether. When you sweat, you lose sodium as well.
Again, do NOT workout. Just lie down in bed and watch TV. That's all you should be doing. By resting, your body isn't forced to split energy in multiple directions. When you lie there, it can devote almost all of its resources to fighting whatever is invading, meaning you get better faster.
For many, you don't need crazy medicines to kill the invader. I always just take an Advil whenever I feel there's a fever that won't break. When I have a sore throat, I'll slowly lick some honey off a teaspoon. For an upset stomach, I get some ginger chews. Though I'm not a homeopathic devotee, I did work in one of those organic markets and tried a lot of different products for a lot of different things. Most, unsurprisingly, ended up being lies, but there were a few grains of truth hidden in there -- ginger and honey being two of them.
A Note on Medicine
As for stronger medication, that's completely up to your doctor. I have no medical degree and can only vouch for my own immune system and what works for it. If something doesn't feel right, go see your doctor. Better a $50 visit now than a $2,000 hospital bill later.
Co-host of HeroesForge, founder of Battle to Be Better, gamer, singer and all around happy person.