High fasting blood sugar but normal during day

How are you sweetening your coffee? What you add to your cup may affect your blood sugar levels.

Whether you were recently diagnosed with type 2 diabetes or have been living with the condition for several years, you know how fickle blood sugar levels can be, and how important it is that they stay controlled.

Proper blood sugar control is key for warding off potential diabetes complications, such as kidney disease, nerve damage, vision problems, stroke, and heart disease, according to the National Institutes of Health (NIH). Plus, keeping your levels in check on a daily basis can help you stay energized, focused, and in a good mood, explains Lisa McDermott, RD, CDCES, a diabetes specialist with the Pittsburgh-based Allegheny Health Network.

According to the American Diabetes Association (ADA), proper medication, effective meal planning, regular exercise, and regular blood sugar checks can all help you keep your levels within a healthy range. The ADA recommends blood glucose stay within 80 to 130 milligrams per deciliter (mg/dL) before meals and below 180 mg/dL two hours after the start of a meal. Furthermore, the organization recommends getting an A1C test, which measures your average blood glucose over the past two to three months, at least twice per year if your levels are stable and you are meeting treatment goals.

RELATED: 5 Ways to Lower Your A1C

Learning how different habits can cause your blood sugar to fluctuate can help you better predict how your levels will swing. Both low and high blood-sugar levels lead to serious health consequences. High blood sugar may cause nausea, vomiting, or shortness of breath, while low blood sugar may cause confusion, dizziness, blurred vision, seizures, unconsciousness, or even death, McDermott explains.

Managing the factors that can influence blood sugar can be a balancing act. Even if you keep careful tabs on what you eat and take your medication conscientiously, you will inevitably see fluctuations in your day-to-day levels. After all, some of the factors that affect your readings are out of your control.

But that doesn’t mean you can’t defend against those factors. Read on to learn some of the lesser-known factors that can cause blood sugar swings — and how to adjust accordingly.

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Dehydration Drives Up Blood Sugar

Can dehydration cause high blood sugar? Yes, and it turns out, the two are more related than you may realize: Falling short on fluids can lead to hyperglycemia, as the sugar in your circulation becomes more concentrated, McDermott explains. To make matters worse, high blood sugar can cause you to urinate more, resulting in even more dehydration.

People with diabetes should be especially vigilant about drinking plenty of water or other calorie-free beverages throughout the day to stay hydrated and healthy. Hydration goals vary depending on factors like sex and life stage. Plus, people who are highly active or have high body mass levels have greater fluid needs. If you find plain H2O hard to swallow, try garnishing your glass with a few citrus wedges, frozen berries, cucumber slices, or fresh mint leaves. Unsweetened iced herbal teas, such as raspberry, cherry, or peach varieties, are also wonderfully refreshing — and naturally caffeine-free, she says.

RELATED: 13 Genius Hacks That Can Help You Drink More Water

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Artificial Sweeteners May Alter Blood Sugar Response

Many people with diabetes reach for diet drinks as a substitute for regular soda or juice because they assume that sugar-free beverages won't raise their blood sugar. But a review published in January 2021 in Frontiers in Nutrition suggested that artificial sweeteners may not be completely neutral after all, and may contribute to impaired glucose homeostasis.

But the research isn't definitive — most government and medical institutions maintain that most artificial sweeteners have no effect on blood sugar. So what could be going on? Mayo Clinic suggests that people can experience a “rebound effect” when consuming artificial sugars. They consider the sugar-free food healthy, so end up consuming excessive amounts or eating other carb-filled foods because they think the diet drink lets them “afford” it. The clinic also notes that some noncaloric sweeteners can cause diarrhea, which can contribute to dehydration.

"If you drink a lot of diet soda then you might want to cut back and see if it has an impact on your blood glucose," says Patty Bonsignore, RN, CDCES, a nurse educator at the Joslin Diabetes Center in Boston. Keep things sugar-free by turning to water or seltzer as opposed to regular soda or juice.

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Some Medications Meddle With Diabetes Control

The prescription and over-the-counter medications you take to treat health problems besides diabetes can monkey with blood sugar levels. One example is steroids (used to treat inflammatory conditions, autoimmune disorders, and asthma), which can cause blood sugar to shoot up dramatically, McDermott says. Birth control pills, certainantidepressants and antipsychotics, some diuretics, and nasal decongestants may also cause higher-than-normal readings, while other drugs may lower blood sugar or make it more difficult to recognize signs of hypoglycemia, according to TriHealth. “Even cough drops can affect blood sugar levels,” she says.

Make sure your prescribing physicians are aware of your diabetes before giving you a new Rx, and consult with your pharmacist before taking any new medications, prescription or not, McDermott advises. Ask whether these products will interfere with diabetes management or interact with any other meds you're taking.

RELATED: Does Metformin Cause Weight Loss?

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Watch Out for the Infamous ‘Dawn Phenomenon’

It's not uncommon to wake up to a high blood sugar reading, even if your number was in the green zone when you went to bed. You may be experiencing the "dawn phenomenon," which occurs when the body preps for waking up by releasing cortisol and other hormones, between 2 and 8 a.m., according to the Mayo Clinic.

These hormones make the body less sensitive to insulin, and in people with diabetes, can contribute to a morning blood sugar spike. Alternatively, you may start the day with a low glucose level if, for example, you're taking too much insulin or medication at night or not eating enough in the evening, McDermott says. She notes that eating a small, protein-rich, low-carb snack at bedtime can sometime help by shortening the fast (without spiking nighttime blood sugar).

If you see a trend in your morning readings — or they're highly erratic from day to day — you'll want to work with your doctor or diabetes educator to identify the problem so you can take steps to correct it, says Bonsignore.

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Women's Menstrual Cycles Can Affect Blood Sugar

As if cramping, bloating, and mood swings weren’t bad enough, hormonal changes during a woman's premenstrual phase can cause her blood sugars to get a little out of whack, according to Women’s College Hospital.

While the effect varies from person to person, some women with diabetes become less sensitive to insulin during the week or so leading up to their period, which can translate into above-normal sugar levels, McDermott explains. Readings typically return to normal once or soon after menstruation begins. If you notice that your blood sugar consistently runs high the week before your period, it may help to trim the amount of carbohydrates you're eating during that time or squeeze in some extra exercise, she says. (Just be sure to track your cycle and blood sugar levels closely to be certain this is the cause.)

If you're taking insulin, speak with your doctor or diabetes educator about possibly adjusting your medication to compensate for hormonal changes.

RELATED: The Top Foods That Tend to Spike Blood Sugar

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Insufficient Sleep Can Throw Blood Sugar Out of Whack

Restless nights hurt more than your mood and energy — they may also spell trouble for your blood sugar. A review published in December 2015 in Diabetes Therapy concluded that a lack of sleep may hinder glucose control and insulin sensitivity in people with type 2 diabetes.

"Sleep is restorative," Bonsignore says. "Not getting enough sleep is a form of chronic stress on the body, and anytime you have added stress, you're going to have higher blood sugar levels."

Unfortunately, people with type 2 diabetes commonly report troubles sleeping, McDermott says. Those with high body-mass indexes are at particular risk for sleep apnea, in which breathing frequently starts and stops during sleep.

To improve your sleep quality and duration, work to get into a consistent sleep routine where you go to bed and wake at the same time every day. Your goal: Nab seven to nine hours of sleep per night, per recommendations from the National Sleep Foundation. If you continue to have sleep troubles or suspect you have sleep apnea (maybe your partner complains about your snoring?), reach out to a sleep medicine specialist for support, Bonsignore says.

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Extreme Weather Can Hinder Diabetes Management

Whether it's swelteringly hot or bitterly cold outside, extreme temperatures can interfere with diabetes control. That’s because people with type 2 diabetes vary in the way their body responds to heat, Bonsignore says. Some may see their blood sugar creep up on really hot days because the unpleasant conditions put extra stress on their system; others, particularly those taking insulin, may experience the opposite effect, she says.

What’s more, high temperatures can affect the way the body uses insulin and potentially lead to blood sugar swings, according to the Centers for Disease Control and Prevention. It also notes that chronically high blood sugar levels can affect the body’s ability to regulate its temperature while also causing the body to lose fluids more quickly. The latter can further stoke blood sugar levels by increasing the risk of dehydration. Try to stay indoors during the hottest part of the day, and monitor your blood sugar closely for changes when the mercury starts to rise, recommends Bonsignore.

RELATED: 8 Best Fruits for a Diabetes-Friendly Diet

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Traveling Can Disrupt Routines, and Thus Sugars

Skipping a few time zones during a long flight throws almost everyone off, but it's an even bigger concern for people with diabetes. The time change can disrupt your medication schedule and cause unusual eating and sleeping habits, which interfere with blood sugar control, McDermott says.

Plus, when you’re on vacation or traveling, you may eat more, drink more alcohol, or be more active — all of which can cause blood sugar swings. She advises checking your blood sugar more frequently while traveling to catch any concerning trends before they become serious problems.

McDermott also recommends packing healthy carb-balanced snacks as well as a refillable water bottle to help you stay hydrated. Try to eat something every four hours throughout the day, even if it can’t be at the exact same times you usually eat. If you take insulin and you're shifting time zones, be sure to work out a medication schedule with your diabetes care team before your trip so you don't mistime any doses, she says.

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Too Much Caffeine Can Give Blood Sugar a Jolt

According to Mayo Clinic, consuming up to 400 milligrams (mg) of caffeine per day is safe for most people, but in those with diabetes, the substance may affect how insulin behaves, which can lead to low or high blood sugar. Prior research suggests that consuming too much caffeine may cause blood sugar levels to spike in those who already have the disease. To make things even more confusing, a different study, published in January 2015 in the Journal of Clinical and Diagnostic Research, suggested that caffeine intake can actually improve how the body manages blood sugar and reduce the risk of diabetes-related complications.

It may depend on the person. “Some people with type 2 diabetes can drink all of the caffeine they want, while others see blood sugar levels spike with just one cup of coffee,” McDermott says.

All you can do is monitor your blood glucose to observe how caffeine affects you. If you experience frequent blood sugar swings and are a heavy consumer of caffeinated beverages (which include diet soda as well as coffee and tea), consider cutting back to see if your glucose control improves, Bonsignore recommends.

RELATED: 10 Beverage Dos and Don’ts for Diabetes

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Blood Sugar Testing Mistakes May Cause Inaccurate Readings

If you don't remember to wash your hands before checking your blood sugar, you may experience a false alarm. Testing after handling food can produce an erroneously high reading because sugar residues on the skin can contaminate the blood sample, research has shown. If your blood sugar readings come back as higher than it really is, you could easily end up taking too much insulin, MsDermott says. The result: dangerously low blood sugar levels.

Today's blood sugar meters are highly sensitive because they use a very tiny draw of blood, which means it can be easy to throw off the glucose concentration in the sample. If you can't get to a sink to give your hands a good scrub, you can improve testing accuracy by using the second drop of blood after wiping away the first.