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How Does Coffee Affect Blood Sugar


Coffee Before A Glucose Test

Many annual wellness checkups require an overnight fasting blood test. Your doctor wants you to fast because food and drink may alter your results, according to . Sugar, fats, enzymes, minerals and cholesterol will absorb into your bloodstream and may change the test results. Alcohol should also be avoided during your fast.

Coffee before a glucose test can affect the results, especially if you add cream and sugar, according to Mercy Health, a chain of hospitals and health care clinics in Ohio and Kentucky. Added sugar and fat from the cream can make your test results inaccurate. Even without these ingredients, however, coffee and a blood sugar test don’t go well together.


Mercy Health suggests asking your doctor for detailed instructions before a fasting test. Also, if you make a mistake and accidentally eat or drink something before your test, let the lab staff know, and they will determine if you need to reschedule the procedure.

Most fasting tests, however, do allow you to have water. Water hydrates your veins and makes it easier to draw the blood out of them, according to Medline Plus.

Read more:Fasting Blood Test Requirements


Planning The Coffee Experiment

I designed the following experiment: I would drink a cup of coffee and measure my blood-sugar levels two hours prior to and after drinking it. Then I would analyze the data to see if drinking coffee seemed to raise my blood-sugar levels.

To increase the reliability of the experiment, I made sure of four things:

1. I would drink the coffee black nothing would be added to it.2. I wouldnt eat or drink anything else, feel stressed, nor do any form of exercise, 2 hours prior to and after drinking the coffee.3. I would eat ketogenic.4. I would go to bed and wake up around the same time as I normally do.

It was coffee time.


Effect Of Caffeine On Blood Sugar Levels

The subject of caffeine’s effect on blood sugar has always been a debate. Talking about coffee, some studies suggest that if a healthy person consumes coffee in moderation, it can reduce the risk of developing diabetes. Consuming 300400 mg of caffeine is considered safe; if caffeine is taken as a coffee, without any sugar, it is healthy. The effect of coffee depends on the age, body mass index and gender of every other person. However, if a person already has diabetes, coffee consumption can contribute to the fluctuations in blood sugar. Ideally, diabetes patients should avoid coffee. They can opt for decaffeinated coffee without sugar.

How Much Caffeine Is Too Much Caffeine


In general, the FDA has recommended 400 mg of caffeine as the maximum limit a healthy adult should drink a day. If you already have diabetes, however, a lower limit may be beneficial. For some people with diabetes, drinking more than 200 mg of caffeineor half the amount for a healthy adultmay negatively impact blood sugar.

What Exactly Is Diabetes

Does Coffee Affect Blood Sugar And Diabetes?

With diabetes, your body is either not producing enough insulin or not using it efficiently . Insulin is a hormone that is normally released by your pancreas to help you take the sugar you eat and move it into your cells where its converted into energy.

If you cant make insulin or your body cant use it, your cells wont be able to absorb sugarand it builds up in your blood instead. This can lead to hallmark symptoms of diabetes like excessive thirst and urination, tiredness, and dizziness. Diabetes can also increase your risk for serious complications like kidney disease, vision loss, nerve damage, and heart disease. 


Surprising Things That Can Spike Your Blood Sugar

When you first found out you had , you tested your blood sugar often to understand how food, activity, stress, and illness could affect your blood sugar levels. By now, youve got it figured out for the most part. But thenbam! Something makes your blood sugar zoom up. You try to adjust it with food or activity or insulin, and it dips really low. Youre on a rollercoaster no one with diabetes wants to ride.

Do you know all of these blood sugar triggers?

Knowledge is power! Look out for these surprising triggers that can send your blood sugar soaring:


  • the pain causes stress, and stress increases blood sugar levels.
  • Artificial sweetenersmore research needs to be done, but some studiesexternal icon show they can raise blood sugar.
  • Coffeeeven without sweetener. Some peoples blood sugar is extra-sensitive to caffeine.
  • Losing sleepeven just one night of too little sleep can make your body use insulin less efficiently.
  • Skipping breakfastgoing without that morning meal can increase blood sugar after both lunch and dinner.
  • Time of dayblood sugar can be harder to control the later it gets.
  • Dawn phenomenonpeople have a surge in hormones early in the morning whether they have diabetes or not. For people with diabetes, blood sugar can spike.
  • Dehydrationless water in your body means a higher blood sugar concentration.
  • Nose spraysome have chemicals that trigger your liver to make more blood sugar.
  • Gum diseaseits both a complication of diabetes and a blood sugar spiker.
  • Coffee May Not Be To Blame

    But what about the studies that show that coffee may protect against type 2 diabetes?

    A year ago, The Journal of the American Medical Association reported that people who drank at least 3-4 cups of coffee per day3-4 cups of coffee per day had a nearly 30% lower risk of developing type 2 diabetes.

    Here’s the catch. In the new study, caffeine came from a pill. But most people get their caffeine from drinks that have other ingredients.

    “Coffee contains many other substances besides caffeine, such as , , and ,” write the researchers, who included Robert Ross, PhD, of Queen’s University. Perhaps those other substances are helpful, but that’s not certain.


    The study appears in the March issue of Diabetes Care.

    Diabetes Care

    Caffeine And Blood Sugar Levels

    Regular high caffeine consumptio, over a 4 week period, has been shown to impair insulin sensitivity in people with type 2 diabetes.

    Whilst the researchers found a relationship between higher coffee consumption and lower sensitivity to insulin, they recognised that the rapid transition to having more coffee may have produced an atypical or emphasised response by the body.


    Effect Of Coffee On Blood Sugar Level If You Are Not Diabetic

    Let us begin by first understanding the effect of coffee on people who are not suffering from diabetes already. The following are the effects:

    • Coffee reduces the risk of contracting type 2 diabetes if you consume a moderate amount of coffee.
    • Studies have proved that with every cup of coffee consumed, the risk of getting the above disease is reduced by 4-8%.
    • In the short term, the drinking of coffee can lead to increased blood sugar level of the body causing diabetes. However, the same may not be true in the long term.
    • Finally, the long- term benefits of coffee come from the fact that if your body is habituated to the caffeine present in coffee, the blood sugar level will not be affected and that is why in the long term, coffee will not lead to increased blood sugar level or even diabetes.

    What Is It About Coffee That Affects Blood Sugar

    The majority of people with diabetes see a spike in their blood sugar when drinking coffee, and its not a mystery that a lot of the cause can be attributed to the caffeine content in your morning cup.


    According to the Mayo Clinic, for people with diabetes, about 200 milligrams of caffeine can cause a spike. Caffeine causes insulin resistance and can negatively affect postprandial blood sugar levels, essentially requiring you to take more insulin for foods eaten when you drink caffeinated beverages. Some people even need to bolus for drinking plain, unsweetened, black coffee that has no carbohydrates.

    Ironically, long-term coffee consumption is associated with higher insulin sensitivity and lower rates of type 2 diabetes, but in the short term, the caffeine content causes a spike in blood sugars and lower insulin sensitivity. Caffeine is also an appetite suppressant, so its overall effect is sometimes balanced out.

    The best option for people with diabetes who are struggling with blood sugar spikes post cup, however, may be to opt for decaf: drinking decaffeinated coffee seems to curb blood sugar spikes in individuals.

    Do You Need More Insulin For Coffee


    To better determine coffees impact on your blood sugar, create a simple experiment on a morning when you wake up with an in-range blood sugar. Drink a cup of coffee and see where your blood sugar goes during the 1 to 2 hours after that cup of coffee.

    Many people simply find they need 1 unit of fast-acting insulin with a cup of coffee. 

    Or you could test your bodys response to coffee by removing coffee from your morning routine for a few days. Did your insulin needs drop? Were your blood sugars easier to manage? If so, that doesnt mean you cant go back to drinking coffee, but it does tell you that you need insulin to help your body deal with the effects of coffee. 

    It also tells you that limiting your coffee intake is likely a good idea!


    The Short Term: Caffeine Reduces Insulin Sensitivity

    Since coffee on its own doesnt contain carbohydrates, simply drinking a cup shouldnt raise glucose levels. To test its effect on glucose metabolism, researchers typically ask study participants to consume either caffeine or coffee with a meal or an oral glucose tolerance test and then monitor their insulin and glucose levels. What theyve found is that insulin and glucose levels tend to rise. That suggests that caffeine causes a decrease in insulin sensitivity since the elevated insulin isnt bringing down the glucose increase from the ingested carbs. In other words, caffeine seems to impair insulins effectiveness. Research has shown that insulin sensitivity drops in response to a single dose of caffeine following 72 hours of caffeine avoidance. It also drops after high coffee consumption over four weeks, suggesting the body does not build a tolerance to caffeines effect on insulin over time. 

    Research shows the same effects in people with Type 2 diabetes, but the impact may last longer given their existing metabolic impairment. One study at Duke University looked at how consuming the caffeine equivalent of about five cups of coffeehalf at breakfast, half at lunchimpacted participants glucose levels throughout the day. It found that caffeine raised their glucose responses to breakfast, lunch, and dinner, as well as causing an increase in their overall average glucose for the day. 

    Caffeine’s Buzz Is Common

    Does Coffee Really Raise Blood Sugar Level


    Just about everyone has at least some caffeine every dayeveryone has at least some caffeine every day, and the numbers are rising for people aged 2-54 years.

    Nearly 90% of U.S. adults and 76% of children have caffeine on a daily basis. Soft drinks are the top source for kids; for adults, coffee is No. 1, followed by soft drinks and teas. That’s according to a study in January’s Journal of the American Dietetic Association.

    Checking nutritional labels doesn’t always help. Food and drink makers don’t have to list the amount of caffeine on the Nutrition Facts label.

    Want to start tracking your caffeine? Here’s how much caffeine is in popular drinks:

    • Coffee : about 135 mg
    • Caffeinated tea : about 50 mg
    • Coca-Cola : about 34.5 mg
    • Diet Coke : 46.5 mg

    Lean And Healthy Subjects

    Moisey et al. showed that compared with caffeinated coffee the decaffeinated beverage improved the glucose metabolism. They studied 10 healthy men in a crossover randomised clinical trial ; caffeinated and decaffeinated coffees were taken 1h after a high glycaemic index meal . Compared with decaffeinated coffee, the caffeinated coffee resulted in 145.6% and 28.5% greater 2h AUC for glucose and insulin , respectively. In addition, the insulin sensitivity was significantly reduced by 40% after ingestion of caffeinated coffee compared with decaffeinated coffee. Gavrieli et al. reported no significant effects of caffeinated coffee on glucose and insulin concentrations, and AUCs compared with control . In this crossover RCT, 16 healthy males and females were evaluated for coffee intake after 3h postprandial response.

    Coffee Does Not Seem To Raise My Blood

    The graphs below show my blood-glucose levels over a 4-hour period for three separate experiments. The blue line is the blood glucose on a morning I drank coffee. The red line is on a morning without coffee.

    Experiment one

    The first experiment indicated that coffee may raise my blood sugar. But only slightly:

    The graph above could suggest that drinking coffee prevents my blood-sugar levels from dropping to the same levels as the morning when I didnt drink coffee.

    Experiment two

    The second experiment indicates that coffee does NOT noticeably raise my blood sugar. Theres a lot of variety in my blood-glucose levels on these two days, but to us it seems that coffee does not raise my blood sugar relative to not drinking coffee .

    Experiment three

    The third experiment also suggests that coffee does not raise my blood sugar much. My blood-sugar levels are quite flat, both on the morning when I drank coffee and the morning I didnt, indicating that the coffee didnt impact my blood-sugar levels much.

    Is Coffee Safe If I Have Diabetes

    Although the evidence on coffee benefits is mixed, as long as you keep an eye on your blood sugar and stick to coffee with less sugar, drinking coffee should be safe. You can treat coffee like any other food, watching how much sugar you add and making sure you limit your caffeine consumption to reasonable amounts. Below are some things to keep in mind.

    Data Synthesis And Analysis

    Data summary of the studies are presented in , . The studies are organised as short-term and long-term effects . The units of glucose and insulin were standardised according to the International System of Units: mmol/L for glucose and pmol/L for insulin. Data are presented as mean±SEM . SEM was used to standardise the study data variability. For studies reporting standard deviation , the SEM was calculated dividing the SD by the square root of the sample size of the corresponding arm of the trial.

    Drink Decaffeinated Coffee Instead

    If you have diabetes, just having about 200 milligrams of caffeine can affect your blood sugar. This is the amount of caffeine you get in about one or two cups of brewed coffee or three or four cups of black tea. This means black coffee is a better option for people with diabetes.

    However, different people may react to it differently, depending on certain factors like age, weight and how much caffeine one usually takes.

    If you have diabetes but can’t do without a cup of coffee in the morning, experts suggest drinking decaffeinated coffee. This will help you get the benefits of other compounds in coffee such as magnesium, chromium and polyphenols without affecting insulin sensitivity.

    Some studies suggest that the antioxidants in coffee can help reduce inflammation in your system and lower your odds of getting type 2 diabetes in the first place.

    Does Sugar Or Coffee Creamer Raise Blood Sugar Levels Of Diabetics

    Dairy products, coffee s, flavors, creamers, and fatty foods can spike up blood sugar levels. Coffee creamers and sweeteners contain saturated fats or actual sugars such as dextrose and maltodextrin in Splenda and so they raise blood sugar levels. Regular consumption of high sugary drinks, coffee with added tables sugar, sweeteners, or creamers increases the risk of type-2 diabetes or causes high blood sugars.

    What Happens If I Do Drink Coffee Before My Glucose Test

    If you dont fast before a glucose test, the results may not be accurate. 

    If you forget and eat or drink something, call your provider and check whether the test is still ok to be carried out.

    Some tests can be analyzed with a note that it was performed when the patient wasnt fasting. However, this may give variable results.

    Always be honest if youve had any food or beverage other than water, even if you did have a cup of coffee before your glucose test, or a snack, or even a meal. 

    The important piece of advice is to tell the technician who is performing the test. They should then make a note of this point to review the results with the food intake as a variable.

    If, however, fasting is an absolute must for meaningful results, they will reschedule the test.

    The Long Term: Drinking Coffee Lowers Type 2 Diabetes Risk

    Does black coffee affect blood sugar?

    If caffeines negative short-term effect on glucose metabolism is well established, so is coffees desirable impact on the risk of Type 2 diabetes. That coffee lowers ones risk of developing diabetes has been in , as well as in large population studies. 

    for a median duration of 5.8 years, found that adults who consumed at least one cup of coffee per week had a 22% lower risk for prediabetes and 34% risk reduction for Type 2 diabetes compared to people who didnt drink coffee. Another study, which followed around 88,000 women in the US with no history of diabetes, found that , with regular coffee offering a slight edge over decaf. Drinking more cups was associated with lower riskwomen who drank one cup per day saw a 13% reduction in relative risk, while women who drank four or more cups saw a 47% reduction.

    That decaf demonstrates nearly the same benefits as regular coffee suggests that something other than caffeine is driving the protective effect. The most likely candidate is chlorogenic acids, members of a group of antioxidant-rich micronutrients called polyphenols, abundant in plant-based foods. 

    Chlorogenic acids may improve glucose metabolism in several ways, according to studies in animals and cell lines:

    Can Caffeine Affect Diabetes

    You know that whatever you eat, it directly affects your blood sugar. But what are the effects of caffeine; in this case, many studies show that drinking coffee can reduce the risk of developing diabetes. If you are already a diabetic patient, its effects may vary from person to person. Apart from this, the impact of caffeine also depends on the amount consumed. If your blood sugar level is already high, then you should reduce caffeine intake. Consumption of caffeine in moderation without sugar may be healthy for diabetes patients.

    Also Read: Moringa Tea: A Unique Tea With Amazing Health Benefits

    Effect Of Coffee On Blood Sugar Level If You Are A Diabetes Patient

    Let us now understand what is the effect of Coffee on a person suffering from diabetes.

    If you are suffering from type 2 diabetes, drinking coffee could be harmful to your health. This is because when you are taking in coffee just before eating, it increases the level of glucose in the blood. This is particularly true for people who are not habituated of drinking coffee in the long run.

    Drinking Coffee increases blood sugar level in the short Term but Decreases Chances of Type 2 Diabetes in the Long Term

    As seen in the above paragraphs, it sounds a little strange that drinking of coffee increases the sugar level in the blood in the short- term. This, in turn, is harmful to diabetes. However, coffee drinking seems to be useful in the long run. Let us understand why the same happens:

    Test For Gestational Diabetes

    If you’re at low risk for developing diabetes while pregnant, your doctor may request a nonfasting test. The American College of Obstetricians and Gynecologists recommends a one-hour blood glucose challenge test between 24 and 28 weeks of pregnancy.

    You may get tested earlier in your pregnancy if you have any of three possible risk factors, according to the Mayo Clinic:

    • If you had gestational diabetes in an earlier pregnancy.
    • If you have a family history of diabetes.
    • If you are have obesity.
    • If you have a metabolic condition associated with the development of diabetes, such as metabolic syndrome or polycystic ovary syndrome.

    If you are found to be at risk, or your one-hour test results have a suspicious value, then you’ll be asked to take a three-hour fasting blood test similar to the blood test given for people with type II diabetes. That will mean no eating or drinking anything but water for eight to 12 hours before your test.

    Read more:4 Food Tips if You Have Gestational Diabetes

    Does Caffeine Affect Blood Sugar

    The average U.S. adult consumes about two 8-ounce cups of coffee a day, which can contain around 280 milligrams of caffeine. For most young, healthy adults, caffeine doesn’t appear to noticeably affect blood sugar levels, and consumption up to 400 milligrams a day appears to be safe. Some studies suggest that drinking coffee, caffeinated and decaffeinated, may actually reduce your risk of developing diabetes. If you already have diabetes, however, the impact of caffeine on insulin action may be associated with higher or lower blood sugar levels. For some people with diabetes, about 200 milligrams of caffeine or the equivalent of one to two 8-ounce cups of plain, brewed coffee may cause this effect. Caffeine affects every person differently. If you have diabetes or you’re struggling to control your blood sugar levels, limiting the amount of caffeine in your diet may provide a benefit.Continue reading >>

    Can You Drink Coffee The Morning You Have A Fasting Blood Sugar Test

    Glucose provides a major source of fuel for your body. When everything is working correctly, your cells absorb glucose from your bloodstream and either use it for energy or store it for later. Problems can occur when your body is unable to utilize glucose properly. Your doctor orders a fasting glucose test to help diagnose glucose metabolism problems such as pre-diabetes and diabetes. Your doctor might also order a fasting glucose test to check how you’re managing your blood sugar. Eating or drinking beverages can alter your test results. Video of the Day A fasting glucose test measures the level of glucose in your blood during a fasted state. This type of test requires that you avoid food and beverages for at least eight hours. You can drink water, but cannot consume coffee or any other beverage. To make it easier, schedule an early morning appointment after a full night’s sleep. This way, you can sleep for eight hours and go to your appointment upon waking. Feel free to take some coffee with you in a thermos to have right after your test is complete.Continue reading >>

    Other Factors That Contribute To Higher Blood Sugars

    The caffeine content in coffee is not the only thing to blame for higher blood sugar levels, however. Many people prefer coffee first thing in the morning, right when theyre often already experiencing the higher blood sugars associated with the dawn phenomenon, and combining the two can make it harder to get levels back under control.

    Photo credit: iStock

    Additionally, beware of added sugars, syrups, and sweetened-dairy products that can quickly add empty calories to your morning brew. The difference in carbohydrate counts between one cup of black coffee and a Grande Frappuccino from Starbucks is stark and can make all the difference between a good blood sugar day and a difficult one. Having coffee beverages that are high in saturated fat and sugar on a regular basis can contribute to both insulin resistance and the development of type 2 diabetes.

    Even an innocuous latte can still have anywhere between 12-25 grams of carbohydrates, simply from the sugars found in milk.

    What Are You Adding To Your Coffee

    Even though those flavored creamers are a mere tablespoon of liquid, they are very high in sugar. Enough sugar to definitely cause an even larger spike in your blood sugar.

    One of the most useful things you could do for yourself as a coffee drinker with diabetes is to gradually adjust your tastebuds to appreciate the taste of black coffee.

    Try removing the sweetener and milk from your coffee for two weeks. Just two weeks! And see how you start to like the taste of black coffee! You might be surprised to find that you eventually find sweetened coffee to taste overwhelmingly sweet.

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