Pre-workouts are one of the most popular options in the supplements category.
If you're wondering if you can take your pre-workout twice in one day, then this guide will help you decide whether that's a safe route or not.
With ingredients like caffeine and other stimulants, it's likely that you shouldn't take your pre-workout twice in one day, especially considering that caffeine has a long half-life that may interfere with a good night's sleep.
The quick answer is that you should only take pre-workout once per day, before your workout (see how long pre-workout takes to kick in).
One serving of pre-workout usually has more than enough caffeine and energy that you'd be overdoing it by taking it twice per day.
If you wake up early enough, you may take pre-workout in the morning and then again in the afternoon, but it's advisable not to exceed more than 300-500mg of caffeine per day, with the former being the recommended maximum.
Even if you work out twice per day, it's advisable to take only one serving.
Ingredients in pre-workouts are designed to be used in one serving, taking more will not be more beneficial if it's already clinically dosed.
The good pre-workouts have full clinical dosages, and any more than those dosages, then you won't be getting more of a benefit, it'll just be diminishing returns.
They are designed to be taken once per day, and any more than that, you'll be putting your health at risk.
Using more than 500-600mg of caffeine per day can increase the risk of health complications. 
Depending on the pre-workout that you go with, some pre-workouts may have 600mg of caffeine per serving, and if you take double that amount then you'll be putting yourself at risk for seizures and other health complications. 
And what's more is that some pre-workouts contain vitamin B3 (niacin) in high dosages, around 25mg, and if you take the upper limit of 35mg, you'll be at risk for liver damage and other health complications. 
Pre-workouts can last for around 8 hours, while still leaving caffeine in your system after that as caffeine has a half-life of 6 hours.
Furthermore, pre-workouts can contain other stimulants like yohimbine and even more risky ones like DMHA and DMAA.
By taking pre-workouts twice per day, you'll be putting yourself at unnecessary risk as they are generally designed to be taken once per 24 hours.
We recommend taking pre-workouts only once per day, before your workouts, and early enough so it doesn't interfere with your sleep.
If you're taking a non-stimulant pre-workout then you'll need to be careful and ensure it doesn't have ingredients that may cause health complications at double the serving.
Below we'll list the ingredients that you should avoid taking twice per day...
The ingredients listed below are ingredients that you should avoid taking twice per day.
Why you should avoid taking them twice per day because they give a rush of energy and not only can they interfere with your sleep but they can also increase the risk for health complications.
There simply isn't enough research to prove the safety of these ingredients to be taken once per day, let alone twice per day.
And doubling the dosage of these ingredients will definitely increase the risk of side effects like jitters, rapid heart rate, elevated blood pressure, headaches, nausea, shortness of breath, anxiety, and more.
If you really wanted to take ingredients like these twice per day, then you'd need to look up the maximum daily dosages of each ingredient.
These are ingredients that you should avoid taking twice a day:
These ingredients can be safely taken twice per day depending on their dosages.
Generally, you don't want to exceed 400-500mg of caffeine per day, especially if you're not used to it.
Remember there are still other foods and beverages that contain caffeine so it's not just the pre-workout dosages that you should be wary about.
These ingredients can generally be taken twice per day safely depending on their dosages.
Some ingredients don't have benefit beyond a certain dosage, like pure citrulline at 10 grams.
These are the ingredients that can possibly be taken twice per day.
Although these ingredients are safe, you should still consult with a healthcare physician before using any dietary supplement and only purchase from companies that have a good reputation.
And they are designed to be taken on an empty stomach.
If you still want to take your pre-workout twice in one day, depending on your training and the type of supplement you're using, then you'd likely be able to in one of these options.
Option #1: Once in the morning and once in the afternoon.
This option is common as some people like to either do cardio or sports in the morning then resistance or more another athletic activity in the afternoon.
You may use a stimulant-based pre-workout in the morning, then a nitric oxide formula, or a non-stimulant pre-workout in the afternoon.
Or you can split your pre-workout serving into two for the morning and afternoon activities.
Option #2: You only have a stimulant-based pre-workout
The problem with using your pre-workout multiple times per day can lead to a much faster build-up of tolerance and you'll need more to feel something.
In this case, you can use your pre-workout before your first session then you can drink something flavored for your second session or you can use an intra-workout with BCAA's.
There's a lot of marketing going into pre-workouts.
Companies will go as far as telling you that you need pre-workouts to see results.
While pre-workouts can assist with muscle-building and results, they help you gain an advantage but they aren't necessary.
Most of your results will come from your diet, sleep, lifestyle, and training program.
There might be a few reasons why you might want to take a pre-workout without working out.
One of those reasons might be that you want to take it early enough so it doesn't interfere with your sleep.
Pre-workouts work for at least 6-8 hours so that would work.
Another reason might be you just want the focus and productivity that comes from an energizing pre-workout.
In this case, yes you can, but we recommend limiting this use as tolerance can build up and it won't be as effective for workouts when you need the energy and focus the most.
We recommend looking into nootropics for productive focus and energy.
With pre-workouts, one of the ingredients you should be careful with is caffeine as if you take too much you'll put yourself at risk for health complications.
It's not only caffeine, there are also other stimulants that can make it more likely to experience side effects when they are combined.
With caffeine though, you should limit the daily usage to 400-500mg per day and even that is pushing it if you're using it on a regular basis.
Read here to find out how much pre-workout you should use.
There are many types of pre-workouts, with a wide range of different ingredients.
Some have lots of stimulants, some have more ergogenic aids like citrulline and beta-alanine, and some have both.
With ingredients that have a recommended daily value, and these don't always have long-term research on bigger doses, it's highly recommended to only take your pre-workout before your workout, once a day.
And some pre-workouts have proprietary blends, so you really won't know how much of each ingredient you're getting.
For the safest results, it's best to limit stimulant-based pre-workouts once per day, then a non-stimulant pre-workout if you must workout again.