The number of people who are walking around with high blood sugar without even knowing it is truly staggering. And part of that is because many people don't know what high blood sugar symptoms actually look like.
For starters, there are more than 30 million people in the U.S. living with diabetes, the condition that occurs when your blood sugar is too high, either as a result of insulin resistance (in the case of type 2 diabetes) or as a result of your pancreas not making any or enough insulin (in the case of type 1 diabetes). But a staggering 25% of people with diabetes are unaware they have the disease, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). In addition to that, there are about 84 million people — or more than one in three adults — who have prediabetes, which occurs when blood sugar is higher than normal but not high enough to be called diabetes, and a shocking 90% of those people do not know they have it, according to the Centers for Disease Control (CDC).
“We have so many individuals at high risk today in the US who are unaware, ”True Hatipoglu, M.D., an endocrinologist at the Cleveland Clinic, tells SELF . Given this situation, it is vital to know the signs of high blood sugar and seek medical care if you experience them, Hatipoglu says (along with getting tested if you are asymptomatic but have risk factors).
With that in mind, here are the high blood sugar symptoms you should be aware of, and what to do if you're experiencing them.  What is high blood sugar?
High blood sugar (or hyperglycemia) occurs when there's a buildup of excess glucose in the bloodstream. This is more often a concern for someone with diabetes than it is for someone without it.
Our bodies are typically pretty great at keeping our blood sugar in perfect balance, Deena Adimoolam, MD, assistant professor of endocrinology at the Icahn School of Medicine at Mount Sinai, tells SELF.
Normally, when the glucose that comes from the food we eat enters the bloodstream, the pancreas secretes just the right amount of insulin, the hormone that your body needs to help move glucose from the bloodstream into the body's cells for energy use or storage, the NIDDK explains. This keeps the amount of glucose in the blood within a pretty tight range. "A normal person who has no problem with their ability to control blood glucose should never become significantly hyperglycemic," Dr. Adimoolam says.
What causes high blood sugar?
You may be thinking that high blood sugar is caused just by eating a super-sugary dessert, but it's not really as simple as that. Sure, eating a lot of sugar or carbs can elevate your blood sugar level, but that's typically when your pancreas kicks into gear and creates insulin to move that glucose into cells throughout the body.
But when someone has diabetes, this finely tuned system gets thrown out of whack. In type 2 diabetes — which accounts for 90% to 95% of diabetes in adults — the body either cannot make enough insulin or cannot utilize insulin well, according to the NIDDK. If someone has prediabetes, their blood glucose will be higher than normal but not quite in the type 2 diabetic range yet, per the NIDDK. And in type 1 diabetes, the body does not use insulin or makes very little.
In any case, the result is extra sugar hanging around the bloodstream, making you feel like total crap in the short term and putting your health at risk in the long term.
High blood sugar symptoms
Someone who has been diagnosed with diabetes will be familiar with how it feels to have high blood sugar. (They can also keep tabs on their blood sugar by testing it regularly.) But for the millions of people walking around with diabetes or prediabetes and unaware of it, knowing the signs of high blood sugar could prompt them to seek care and get a diagnosis As soon as possible.
While type 1 diabetes symptoms can come on suddenly and severely, it's important to note that type 2 diabetes symptoms can creep up gradually and be so mild that they're not noticeable, the NIDDK explains. And most people with prediabetes actually have no symptoms, per the NIDDK. So it's extremely important to get screened if you have risk factors, like having a family history, being overweight, being inactive, or being over age 45.
Still, there are many signs of high blood sugar in the short and long term that it does not hurt to be conscious of, especially if you are at elevated risk.
Early on, high blood sugar can make you feel off in a variety of ways.
Feeling tired may be the most common early sign of high blood sugar, Dr. Hatipoglu says. It's also one that can occur, to a mild degree, with even the mild and normal blood sugar fluctuations that occur in people without diabetes (or with prediabetes) when they consume a large amount of simple carbs, like sugar, she says.  Of course, tiredness is a pretty nonspecific symptom (and can even be a sign of low blood sugar, as Dr. Adimoolam points out). If you notice fatigue regularly occurring right after you eat, though — especially a carb-heavy meal — it may have to do with rising blood sugar levels. "People will say, 'I want to nap after lunch' or, 'I just cannot open my eyelids after dinner,' often after eating something like a lot of pasta or potatoes or sweets," Dr. Hatipoglu says. In any case, it's a sign to see someone.
2. Frequent urination
When you have too much sugar in your blood, “your kidneys start trying to pour out more sugar to get rid of it. And as they excrete the sugar, they pull out water with it, ”Dr. Hatipoglu explains. This makes you have to visit the bathroom more than usual.
 3. Increased thirst [/h2] This is a natural effect of peeing more, Dr. Adimoolam explains, because your body becomes dehydrated. "People start feeling thirsty all the time," Dr. Hatipoglu says. The dehydration also becomes cyclical, the Mayo Clinic explains: The more you pee, the thirstier you are, the more you drink, the more you pee, and so on.
Dehydration from any cause can trigger headaches, Dr. Hatipoglu says. Of course, headaches can be a sign of many different things, but it's worth getting checked out if it's something new or coupled with other symptoms here. (The dehydration can also worsen your tiredness, by the way.)
5. Blurred vision
When there is excess sugar in the blood, it can affect some unexpected areas in the body, like your eyes. Essentially, extra sugar (along with a little water) gets trapped in the lens in the middle of the eye, causing a blurred effect, Dr. Hatipoglu explains. (This is temporary, and not the same as the damage to the eye that can occur in the long term.)
6. Nausea, vomiting, confusion, and more
These seemingly disparate symptoms are all signs of a rare and life-threatening state called diabetic ketoacidosis (DKA). DKA can cause the symptoms above, as well as stomach pain, trouble breathing, dry or flushed skin, fruity-smelling breath, or difficulty paying attention. It usually occurs in people with type 1 diabetes and is sometimes the first sign they are sick, according to the U.S. National Library of Medicine. (More rarely, DKA can occur to a milder degree in type 2 diabetes.) Unable to use the sugar in the blood for energy without insulin, the liver begins to break down body fat into a type of fuel called ketones at such a high rate that they become toxic and make the blood acidic, the US National Library of Medicine explains. DKA can be fatal if left untreated, so anyone experiencing these symptoms should seek care immediately.
Over time, untreated high blood sugar can cause additional symptoms.
7. Recurrent infections
Consistently elevated blood sugar levels can weaken the body’s immune response, according to the CDC. This makes it harder for your body to fight off some infections, making them more frequent, lingering, or serious.
Dr. Hatipoglu especially tends to see frequent yeast infections in women with diabetes. This is because excess sugar from high blood sugar spilling out through the urine helps feed the bacteria that can cause these infections, the NIDDK says. Women with diabetes are also more prone to UTIs, according to the CDC.
8. Slow-healing sores
High blood sugar levels can affect your body’s circulatory system as well, Dr. Hatipoglu says, impairing blood flow and the body’s ability to heal itself. Sores that take a while to heal, often on the feet, are a common sign of this decreased circulation, according to the Mayo Clinic.
9. Dental issues
Glucose is present in your saliva as well as your blood. When there is too much of it, it helps harmful bacteria in your mouth grow and combine with food particles to create plaque, the NIDDK explains. This leads to issues like tooth decay, cavities, gingivitis, gum disease, and bad breath.
Swollen, tender, and bleeding gums are one of the first things to look out for.
10. Tingling hands and feet
Over the years, having too much glucose in the blood can begin to impact nerve function and eventually cause nerve damage, called neuropathy, Dr. Hatipoglu says. The most common kind of neuropathy is peripheral, according to the NIDDK, which affects the extremities. You might start noticing feelings of tingling, numbness, or burning in your hands, feet, arms, and legs, per the Mayo Clinic.
What to do if you have these symptoms
The good news is that if you are experiencing these symptoms, a trip to a primary care provider is usually enough to tell you whether high blood sugar due to diabetes or prediabetes is the cause. If your doctor suspects you might have diabetes, they may do a finger-stick test on the spot to see your current blood sugar and / or a blood test to see your average blood sugar over the past few months, Adimoolam says. The doctor may also test for certain autoantibodies to determine whether your diabetes is type 1, the autoimmune version of the disease, according to the NIDDK.
High blood sugar treatment and prevention
How you treat and prevent high blood sugar depends on the cause and the individual. But it will almost certainly involve working with your health care team on a plan involving a mix of lifestyle habits and medications to help you best manage your condition.
If the test results indicate you have prediabetes, there are things you can do that may help mitigate or even reverse prediabetes and prevent type 2 diabetes, according to the US National Library of Medicine, including losing weight if you are overweight, exercising, changing your diet (with the guidance of someone like your doctor, an RD, or a certified diabetes educator), and taking prescribed medication.
If you are diagnosed with type 1 diabetes, you will need to test your blood sugar often (with finger sticks and potentially a continuous glucose monitoring system), take insulin everyday (via injections or an insulin pump) when you eat carbs or have high blood sugar, and exercise regularly, according to the NIDDK.
If you are diagnosed with type 2 diabetes, you will also have to monitor your blood sugar, make certain lifestyle changes (like eating a healthy diet and exercising), and potentially take medication (like Metformin and possibly insulin), Dr.
In both type 1 and 2 diabetes, the best way to prevent high blood sugar is to follow your treatment plan and talk to your doctor if something is not working for you.