Why Doesn’t Caffeine Affect Me? (Factors Influencing Caffeine’s Effects or Lack of)

For some, coffee can be a real energy booster. But for others, it's simply a tasty beverage with no effects. What causes caffeine to have no effect on us?

May 7, 2024
An empty coffee mug next to a spilling can of caffeinated beverage.

You're having your usual cup of coffee in the morning, but somehow, it just doesn't quite hit in the same way that it used to. Instead of the usual rush of energy and focus to help you face the day, it feels like nothing has changed. Does caffeine even affect you anymore?

There are plenty of reasons why you might feel this way, and thankfully there are also some solutions to solve them. Let's take a look at some of the reasons why caffeine might not affect you. 

You May Have a High Tolerance

Caffeine is a central nervous system stimulant affecting how the body produces various chemicals like adenosine for sleep, dopamine for mood, and adrenaline for energy [1]. It also speeds up processes like your heart rate and breathing and can boost your energy and focus.

If you regularly consume caffeine, your body will get used to its effects, leading to caffeine tolerance. This means that it learns to work with the caffeine in your system. Over time your body gets used to these increased levels and simply sees them as the new normal. As a result, a higher dose of caffeine is often needed to create a noticeable effect. 

If you’re not feeling anything from your usual cuppa, then your body may simply have developed a tolerance to it. This leads some people to up the ante and increase their caffeine consumption to much higher levels to compensate, which brings problems of its own. 

Related: How To Stop Heart Palpitations From Caffeine?

You’re Having Way Too Much

Having a lot of caffeine may work at first to battle caffeine tolerance, but it won’t last forever. After a while, things get to the point where you’ll need a larger amount just to keep going. You can even reach a stage where you feel withdrawal symptoms just from having less caffeine than you’re used to in your system.

In addition, your body will start to generate more adenosine receptors to try to counteract the blocking effect of caffeine, making it less effective at keeping you energized [2].

If things get to this point, it’s likely you’re consuming far too much caffeine and should consider cutting down. 

Related: How Late Is Too Late for Coffee?

You Might Not Be Getting Enough Caffeine

If you don’t think your cuppa is doing anything, it might be that it simply doesn’t have enough caffeine in it to have an effect. Research has shown that caffeine starts to have an effect at around 100mg [3]. So, if you’re consuming something with a lower caffeine content, such as a cup of tea that has approximately 50mg of caffeine, then you’re probably not getting much of the energizing benefits. 

If this is the case for you, consider switching to a stronger coffee like Vietnamese coffee. You might want to try our workhorse coffee Ha Noi or the strong and mighty Ban Me.

Both of these blends use robusta coffee beans instead of arabica. Robusta has a naturally higher caffeine content than the latter.

You’re Simply Too Tired

Although caffeine can help to perk us up in a pinch, it’s not a miracle worker. If you suffer from poor sleep and use caffeine to keep you going throughout the day, this will work for a time, but not forever [5]. 

Over time if you’re not getting enough sleep, your body will begin to work up a “sleep debt.” As this continues to grow without proper rest, it will eventually become too much even for caffeine to offset.

If you think this is why caffeine isn’t working for you, then try cutting down on your intake. This allows your body to gradually generate enough adenosine, a chemical that makes you sleepy, that caffeine blocks [6]. Set some time aside to catch some well-needed Z’s, and if things don’t improve, you might want to see what your doctor can do for you, too. 

Related: Why Does Coffee Make Me Sleepy?

Your Genetics May Be at Play

If none of the answers above solve the question of why caffeine does not work for you, then it may simply be in your DNA. 

There’s a particular gene called CYP1A2 that affects your body’s ability to metabolize caffeine. People with the “slow variants,” AC and CC genotypes, metabolize caffeine slowly. However, if you have the AA genotype, which is the “fast variant,” then you’re metabolizing caffeine at a much quicker rate. This may be one of the reasons why caffeine has less of an effect on you [7].

Some people are also born with a higher number of neuroreceptors in their brains, including those that pick up adenosine [6]. For these people, there is simply not enough caffeine to block all of the adenosine receptors, reducing caffeine’s energizing effect.

FAQs: Effects of Caffeine

Still need answers? Check out our FAQs on the effects of caffeine and how you may be able to get that buzz. 

1. How do I make caffeine work for me?

This will depend upon your particular circumstances. For example, if you’re drinking too much, you may have developed a tolerance and need to cut down to allow your body to reset its reaction to caffeine. It could also be that you’re having foods and drinks with too low a level of caffeine to have an effect.

Otherwise, it could simply be that caffeine doesn’t work for you. Although you can enjoy a tasty cup of coffee, you might need to look elsewhere for an energy and focus boost. 

2. What are the best caffeine alternatives?

Alternatives to caffeine that have similar effects include ginseng and peppermint. These are other natural stimulants that produce steady energy levels without affecting adenosine in the way caffeine does.

3. Will caffeine and sugar have more effect together?

Studies have shown that caffeine and sugar together can be a powerful combination when it comes to increasing energy and performance [8]. But, the two together can lead to a crash in sugar and caffeine levels a few hours after consumption, and overuse of sugar could lead to long-term health problems such as diabetes. 

4. How much caffeine should I have per day?

The recommended guideline for safe daily coffee consumption from the FDA is 400mg. This normally equates to around 4 8oz coffees, but if you’re drinking Vietnamese coffee, it may be less than this.

Vietnamese coffee has a high caffeine content and is pretty strong. It primarily uses robusta beans and has a higher caffeine content than arabica.

5. How do I reduce my caffeine tolerance?

There are a few ways you can reduce your caffeine tolerance. The first is to consume it less frequently. For example, having a cup of coffee every other day as opposed to daily. The second is to reduce the amount of caffeine consumed, for example switching from robusta coffee like Ban Me and Ha Noi to arabica like Cafely’s Da Lat beans


  1. Ferré, S. (2008). An update on the mechanisms of the psychostimulant effects of caffeine. Journal of Neurochemistry, 105(4), 1067–1079. https://doi.org/10.1111/j.1471-4159.2007.05196.x
  2. Boulenger, J. P., Patel, J., Post, R. M., Parma, A. M., & Marangos, P. J. (1983). Chronic caffeine consumption increases the number of brain adenosine receptors. Life Sciences, 32(10), 1135–1142. https://doi.org/10.1016/0024-3205(83)90119-4
  3. Institute of Medicine (US) Committee on Military Nutrition Research. (2010). Efficacy of Caffeine. Nih.gov; National Academies Press (US). https://www.ncbi.nlm.nih.gov
  4. Vázquez, J. C., Martin de la Torre, O., López Palomé, J., & Redolar-Ripoll, D. (2022). Effects of Caffeine Consumption on Attention Deficit Hyperactivity Disorder (ADHD) Treatment: A Systematic Review of Animal Studies. Nutrients, 14(4), 739. https://doi.org/10.3390/nu14040739
  5. O’Callaghan, F., Muurlink, O., & Reid, N. (2018). Effects of caffeine on sleep quality and daytime functioning. Risk Management and Healthcare Policy, Volume 11(1), 263–271. https://doi.org/10.2147/rmhp.s156404
  6. Ribeiro, J. A., & Sebastião, A. M. (2010). Caffeine and adenosine. Journal of Alzheimer’s Disease: JAD, 20 Suppl 1(20), S3-15. https://doi.org
  7. Mahdavi, S., Palatini, P., & El-Sohemy, A. (2023). CYP1A2 genetic variation, coffee Intake, and kidney dysfunction. JAMA Network Open, 6(1), e2247868. https://doi.org/10.1001/jamanetworkopen.2022.47868
  8. Scholey, A., Savage, K., O’Neill, B. V., Owen, L., Stough, C., Priestley, C., & Wetherell, M. (2014). Effects of two doses of glucose and a caffeine-glucose combination on cognitive performance and mood during multitasking. Human Psychopharmacology: Clinical and Experimental, 29(5), 434–445. https://doi.org