Risk factors for diabetes depend on the type of diabetes.

Risk factors for type 1 diabetes

Although the exact cause of type 1 diabetes is unknown, factors that may signal an increased risk include:

Family history. Your risk increases if a parent or sibling has type 1 diabetes.

Environmental factors. Circumstances such as exposure to a viral illness likely play some role in type 1 diabetes.

The presence of damaging immune system cells (autoantibodies). Sometimes family members of people with type 1 diabetes are tested for the presence of diabetes autoantibodies. If you have these autoantibodies, you have an increased risk of developing type 1 diabetes. But not everyone who has these autoantibodies develops diabetes.

Geography. Certain countries, such as Finland and Sweden, have higher rates of type 1 diabetes.

Risk factors for prediabetes and type 2 diabetes

Researchers don't fully understand why some people develop prediabetes and type 2 diabetes and others don't. It's clear that certain factors increase the risk, however, including:

Weight. The more fatty tissue you have, the more resistant your cells become to insulin.

Inactivity. The less active you are, the greater your risk. Physical activity helps you control your weight, uses up glucose as energy and makes your cells more sensitive to insulin.

Family history. Your risk increases if a parent or sibling has type 2 diabetes.

Race or ethnicity. Although it's unclear why, certain people — including Black, Hispanic, American Indian and Asian American people — are at higher risk.

Age. Your risk increases as you get older. This may be because you tend to exercise less, lose muscle mass and gain weight as you age. But type 2 diabetes is also increasing among children, adolescents and younger adults.

Gestational diabetes. If you developed gestational diabetes when you were pregnant, your risk of developing prediabetes and type 2 diabetes increases. If you gave birth to a baby weighing more than 9 pounds (4 kilograms), you're also at risk of type 2 diabetes.

Polycystic ovary syndrome. For women, having polycystic ovary syndrome — a common condition characterized by irregular menstrual periods, excess hair growth and obesity — increases the risk of diabetes.

High blood pressure. Having blood pressure over 140/90 millimeters of mercury (mm Hg) is linked to an increased risk of type 2 diabetes.

Abnormal cholesterol and triglyceride levels. If you have low levels of high-density lipoprotein (HDL), or "good," cholesterol, your risk of type 2 diabetes is higher. Triglycerides are another type of fat carried in the blood. People with high levels of triglycerides have an increased risk of type 2 diabetes. Your doctor can let you know what your cholesterol and triglyceride levels are.

Risk factors for gestational diabetes

Pregnant women can develop gestational diabetes. Some women are at greater risk than are others. Risk factors for gestational diabetes include:

Age. Women older than age 25 are at increased risk.

Family or personal history. Your risk increases if you have prediabetes — a precursor to type 2 diabetes — or if a close family member, such as a parent or sibling, has type 2 diabetes. You're also at greater risk if you had gestational diabetes during a previous pregnancy, if you delivered a very large baby or if you had an unexplained stillbirth.

Weight. Being overweight before pregnancy increases your risk.

Race or ethnicity. For reasons that aren't clear, women who are Black, Hispanic, American Indian or Asian American are more likely to develop gestational diabetes.

Complications

Long-term complications of diabetes develop gradually. The longer you have diabetes — and the less controlled your blood sugar — the higher the risk of complications. Eventually, diabetes complications may be disabling or even life-threatening. Possible complications include:

Cardiovascular disease. Diabetes dramatically increases the risk of various cardiovascular problems, including coronary artery disease with chest pain (angina), heart attack, stroke and narrowing of arteries (atherosclerosis). If you have diabetes, you're more likely to have heart disease or stroke.

Nerve damage (neuropathy). Excess sugar can injure the walls of the tiny blood vessels (capillaries) that nourish your nerves, especially in your legs. This can cause tingling, numbness, burning or pain that usually begins at the tips of the toes or fingers and gradually spreads upward.

Left untreated, you could lose all sense of feeling in the affected limbs. Damage to the nerves related to digestion can cause problems with nausea, vomiting, diarrhea or constipation. For men, it may lead to erectile dysfunction.

Kidney damage (nephropathy). The kidneys contain millions of tiny blood vessel clusters (glomeruli) that filter waste from your blood. Diabetes can damage this delicate filtering system. Severe damage can lead to kidney failure or irreversible end-stage kidney disease, which may require dialysis or a kidney transplant.

Eye damage (retinopathy). Diabetes can damage the blood vessels of the retina (diabetic retinopathy), potentially leading to blindness. Diabetes also increases the risk of other serious vision conditions, such as cataracts and glaucoma.

Foot damage. Nerve damage in the feet or poor blood flow to the feet increases the risk of various foot complications. Left untreated, cuts and blisters can develop serious infections, which often heal poorly. These infections may ultimately require toe, foot or leg amputation.

Skin conditions. Diabetes may leave you more susceptible to skin problems, including bacterial and fungal infections.

Hearing impairment. Hearing problems are more common in people with diabetes.

Alzheimer's disease. Type 2 diabetes may increase the risk of dementia, such as Alzheimer's disease. The poorer your blood sugar control, the greater the risk appears to be. Although there are theories as to how these disorders might be connected, none has yet been proved.

Depression. Depression symptoms are common in people with type 1 and type 2 diabetes. Depression can affect diabetes management.

Complications of gestational diabetes

Most women who have gestational diabetes deliver healthy babies. However, untreated or uncontrolled blood sugar levels can cause problems for you and your baby.

Complications in your baby can occur as a result of gestational diabetes, including:

Excess growth. Extra glucose can cross the placenta, which triggers your baby's pancreas to make extra insulin. This can cause your baby to grow too large (macrosomia). Very large babies are more likely to require a C-section birth.

Low blood sugar. Sometimes babies of mothers with gestational diabetes develop low blood sugar (hypoglycemia) shortly after birth because their own insulin production is high. Prompt feedings and sometimes an intravenous glucose solution can return the baby's blood sugar level to normal.

Type 2 diabetes later in life. Babies of mothers who have gestational diabetes have a higher risk of developing obesity and type 2 diabetes later in life.

Death. Untreated gestational diabetes can result in a baby's death either before or shortly after birth.

Complications in the mother also can occur as a result of gestational diabetes, including:

Preeclampsia. This condition is characterized by high blood pressure, excess protein in the urine, and swelling in the legs and feet. Preeclampsia can lead to serious or even life-threatening complications for both mother and baby.

Subsequent gestational diabetes. Once you've had gestational diabetes in one pregnancy, you're more likely to have it again with the next pregnancy. You're also more likely to develop diabetes — typically type 2 diabetes — as you get older.

Complications of prediabetes

Prediabetes may develop into type 2 diabetes.

There are different types of insulin depending on how quickly they work, when they peak and how long they last.

Insulin is available in different strengths; the most common is U-100.

All insulin available in the United States is manufactured in a laboratory, but animal insulin can still be imported for personal use.

Inside the pancreas, the hormone insulin is made in the beta cells, which are part of the Islets of Langerhans. These islets also have alpha cells, which make glucagon, as well as delta cells. With each meal, beta cells release insulin to help the body use or store the blood sugar it gets from food.

In the beta cells, insulin is created first as a big molecule called “proinsulin.” Proinsulin is broken into two pieces: insulin and C-peptide. C-peptide is important especially when determining treatment because it can be used to measure how much insulin a person is making. The more C-peptide a person has, the more insulin they are making. This can help a provider determine how much insulin to prescribe. 

In people with type 1 diabetes, the pancreas no longer makes insulin. The beta cells have been destroyed and they need insulin shots to use glucose from meals.

People with type 2 diabetes make insulin, but their bodies don't respond well to it. Some people with type 2 diabetes need diabetes pills or insulin shots to help their bodies use glucose for energy.

Insulin cannot be taken as a pill because it would be broken down during digestion just like the protein in food. It must be injected into the fat under your skin for it to get into your blood. In some rare cases insulin can lead to an allergic reaction at the injection site. Talk to your doctor if you believe you may be experiencing a reaction.

Types of insulin

Rapid-acting insulin, begins to work about 15 minutes after injection, peaks in about one or two hours after injection, and last between two to four hours. Types: insulin aspart (Fiasp, NovoLog) Insulin glulisine (Apidra), and insulin lispro (Admelog, Humalog)

Regular or short-acting insulin usually reaches the bloodstream within 30 minutes after injection, peaks anywhere from two to three hours after injection, and is effective for approximately three to six hours. Types: Human Regular (Humulin R, Novolin R, Velosulin R)

Intermediate-acting insulin generally reaches the bloodstream about two to four hours after injection, peaks four to 12 hours later, and is effective for about 12 to 18 hours. Types: NPH (Humulin N, Novolin N, ReliOn)

Long-acting insulin  reaches the bloodstream several hours after injection and tends to lower glucose levels up to 24 hours. Types: degludec (Tresiba), detemir (Levemir), and glargine (Basaglar, Lantus)

Ultra long-acting reaches the blood stream in six hours, does not peak, and lasts about 36 hours or longer. Types: glargine u-300 (Toujeo)

Premixed insulin can be helpful for people who have trouble drawing up insulin out of two bottles and reading the correct directions and dosages. It is also useful for those who have poor eyesight or dexterity and is convenient for people whose diabetes has been stabilized on this combination.

In 2015 an inhaled insulin product, Afrezza, became available in the U.S. Afrezza is a rapid-acting inhaled insulin that is administered at the beginning of each meal and can be used by adults with type 1 or type 2 diabetes. Afrezza is not a substitute for long-acting insulin. Afrezza must be used in combination with injectable long-acting insulin in patients with type 1 diabetes and in type 2 patients who use long-acting insulin.

Inhaled insulin begins working within 12 to 15 minutes, peaks by 30 minutes, and is out of your system in 180 minutes. Types: Technosphere insulin-inhalation system (Afrezza)

Characteristics of insulin

Insulin has three characteristics:

Onset is the length of time before insulin reaches the bloodstream and begins lowering blood sugar.

Peak time is the time during which insulin is at maximum strength in terms of lowering blood sugar.

Duration is how long insulin continues to lower blood glucose.

Insulin strength

All insulins come dissolved or suspended in liquids. The standard and most commonly used strength in the United States today is U-100, which means it has 100 units of insulin per milliliter of fluid, though U-500 insulin is available for patients who are extremely insulin resistant.

U-40, which has 40 units of insulin per milliliter of fluid, has generally been phased out around the world, but it is possible that it could still be found in some places (and U-40 insulin is still used in veterinary care).

If you're traveling outside of the U.S., be certain to match your insulin strength with the correct size syringe.