Can Caffeine Make You Tired? All You Need to Know

Can Caffeine Make You Tired Instead of Awake?

For some, caffeine does not work as expected. Instead of increasing focus, it leads to brain fog or sluggishness. If you’ve ever asked yourself, why am I still tired after drinking coffee, this might be why.

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This can happen for several reasons, including dehydration, lack of sleep, high caffeine tolerance, or the body’s unique way of processing caffeine.

Genetics also plays a role. Some people break down caffeine quickly, while others metabolize it slowly. Those who break it down fast may not get a long-lasting energy boost. Instead, they might experience a short-lived effect followed by sudden tiredness.

How Can Caffeine Make You Tired? (Signs)

Caffeine blocks adenosine, a neurotransmitter that builds up in your brain throughout the day. This chemical slows down nerve activity and signals your body to prepare for sleep.

Blocking adenosine receptors should create alertness and reduce tiredness. However, the effect is not always the same for everyone. Certain factors can cause a crash, leading to fatigue instead of energy.

Before going into the factors, how can caffeine make you tired? How do you know?

Here are some signs that may indicate caffeine is causing fatigue.

• You feel sleepy even after drinking coffee: Instead of staying alert, sluggishness takes over.
• You get headaches or feel dizzy: Some people feel lightheaded instead of energized.
• Your heart races, but you still feel drained: Your body feels restless, but your brain remains tired.
• You get a short energy boost, then crash: A temporary boost quickly turns into fatigue.
• You feel more anxious or jittery: Instead of focusing, you feel nervous or uncomfortable.

Why Does Caffeine Make Me Tired?

There are several reasons why caffeine can make you feel tired instead of awake.

1. Caffeine Blocks Adenosine, But It Builds Up

Adenosine is a natural chemical in your brain that makes you feel sleepy. Caffeine blocks adenosine receptors, which creates alertness. According to the American Academy of Sleep Medicine, caffeine’s effect can stay in the body for up to 5 hours, with its peak effects occurring within 30-60 minutes after consumption.

However, once caffeine wears off, all the adenosine that was blocked floods your system at once. This leads to sudden tiredness, often called a "caffeine crash".  

2. Blood Sugar Levels Fluctuate

Many caffeinated drinks, especially energy drinks or sweetened coffee, contain high amounts of sugar. This causes a quick spike in energy, followed by a drop in blood sugar, leading to tiredness. Even without added sugar, caffeine can still influence insulin levels, which may affect your energy throughout the day.

Maddie Nielsen, RDH, discusses whether caffeine affects blood sugar in her YouTube video.

3. Dehydration Can Lead to Fatigue

If you've noticed you need to urinate frequently after caffeine, you may be wondering, do caffeine pills make you pee more? Caffeine increases urine production, which makes your body lose fluids faster than usual. This fluid loss can contribute to dehydration and fatigue."

If you don’t drink enough water, dehydration can occur. As a result, this may lead to tiredness, dizziness, and headaches. 

These symptoms may make it feel like caffeine makes you more exhausted instead of energized. Staying hydrated while consuming caffeine can help prevent this issue.

4. Tolerance Reduces Caffeine’s Effects

Drinking caffeine regularly can lead to tolerance, meaning your body gets used to its effects. Over time, caffeine does not provide the same energy boost unless a larger amount is consumed. 

Many people in the U.S. consume around 135 mg of caffeine per day, which equals about 1.5 cups of coffee. According to the FDA, most healthy adults can safely consume up to 400 mg of caffeine daily, which is about four cups of brewed coffee.

However, as tolerance builds, caffeine’s ability to block adenosine weakens, which makes it less effective at preventing tiredness.

5. Caffeine Affects Sleep Quality

Caffeine stays in your system for several hours. Drinking it in the afternoon or evening can make it harder to fall asleep or stay in deep sleep stages. Even if you manage to sleep, the quality may be poor, causing tiredness the next day. 

A systematic review in Sleep Medicine Reviews found that caffeine consumption reduces total sleep time by an average of 45 minutes and decreases sleep efficiency by 7%. It also increases the time it takes to fall asleep and the time spent awake during the night. 

Additionally, caffeine increases light sleep while reducing deep sleep duration, which is essential for feeling well-rested. Since caffeine does not replace restful sleep, consuming it to stay awake can create a cycle of poor sleep and daytime fatigue.

6. Anxiety and Stress Can Affect Caffeine 

People with anxiety or high stress may react differently to caffeine. Instead of feeling focused, they may experience nervousness, restlessness, or a racing heart. 

High-stress hormones combined with caffeine can make you feel drained rather than alert. This can result in mental and physical exhaustion instead of the energy boost expected from caffeine.

7. Withdrawal Symptoms Can Cause Fatigue

If you regularly consume caffeine and suddenly reduce your intake, withdrawal symptoms can appear. One of the most common symptoms is fatigue. Your body gets used to caffeine’s effects; without it, you may feel sluggish and experience headaches or difficulty concentrating.

Withdrawal can last a few days to a week, depending on how much caffeine you consumed before cutting back.

Shannon Kilgore, MD, a neurologist at the Veterans Affairs Health Care System in Palo Alto, California, and Stanford University School of Medicine, was quoted in the AMA as saying,

“Caffeine can also be used medically to treat headache because it improves the absorption of other analgesics. It actually causes vasoconstriction. That by itself can also make the headache go away. So, it can cause headaches, and it can also help.”

Can Caffeine Make You Tired If You Have Anxiety?

Yes, caffeine can have a stronger effect on people with anxiety and depression. It can make them feel jittery, restless, or mentally drained. Instead of focus, there may be discomfort, leading to both physical and mental tiredness.

Caffeine increases stress hormones like cortisol, which can leave a person feeling worn out rather than refreshed. Those who are sensitive to caffeine or already have high stress levels may find that caffeine does not provide energy but instead adds to their exhaustion.

Can Caffeine Make You Tired and Dizzy?

Yes, caffeine can cause dizziness for some people. This happens because caffeine affects blood pressure, hydration, and sugar levels. A fast heart rate combined with low hydration can lead to lightheadedness.

Some people may also feel dizzy if caffeine interacts with medications or health conditions they have. If dizziness happens after caffeine, reducing the amount of caffeine or drinking more water can help.

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Tips to Avoid Caffeine-Related Tiredness

Drinking caffeine the right way can help you stay alert without feeling drained later. Small changes in how and when you consume it can prevent tiredness.

Here are some simple ways to avoid caffeine-related fatigue:

• Drink Water Along with Caffeine: This helps you stay hydrated and avoids dizziness or fatigue.
• Avoid Sugary Energy Drinks: Too much sugar can spike your energy and then leave you feeling drained.
• Limit Caffeine in the Afternoon: If you don’t want it to mess with your sleep, have coffee at least 8.8 hours before bed and stronger caffeine sources 13.2 hours before sleep.
• Don’t Depend on Caffeine for Energy: Good sleep, balanced meals, and regular movement will keep you naturally energized.
• Monitor Caffeine Intake: Too much caffeine makes it less effective. You may be asking, does caffeine tolerance go away? Yes, taking breaks can help you feel the boost again.

Other Reasons for Tiredness That May Seem Like Caffeine’s Fault

Caffeine may not always be the direct cause of tiredness. Other factors can make it seem like caffeine is to blame.

• Iron Deficiency or Anemia: Low iron levels can cause tiredness even after consuming caffeine.
• Thyroid Problems: Thyroid imbalances affect energy, sometimes making caffeine useless.
• Poor Diet: Lack of proper nutrition leads to fatigue that caffeine cannot fix.
• Too Much Stress: Chronic stress drains energy which reduces caffeine’s impact.

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