Diabetes Medications: Types, How They Work, and Side Effects — Complete Guide

Oct 21

9 min read

Updated: 6 days ago

Written and medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: October 2026 · How we review

Quick Answer: What are diabetes medications?

Diabetes medications are prescription drugs that lower blood sugar, used alongside meal planning and physical activity. The three main groups are oral pills, non-insulin injectables such as GLP-1 agonists, and insulin. Everyone with type 1 diabetes needs insulin, while many people with type 2 use pills or injectables. Insulin, sulfonylureas and meglitinides are more likely to cause low blood sugar. [1]

What the research says

Adding insulin glargine or liraglutide to metformin kept blood sugar on target longest. In a trial of 5,047 adults with type 2 diabetes followed for about 5 years, rates of losing A1C control were 26.5 and 26.1 per 100 person-years with glargine and liraglutide, versus 30.4 with glimepiride and 38.1 with sitagliptin. Severe low blood sugar was most common with glimepiride (2.2% vs 0.7–1.3%). (Nathan et al., N Engl J Med, 2022) [2]
SGLT2 inhibitors and GLP-1 agonists protect the heart and kidneys in type 2 diabetes. A network meta-analysis of 764 trials (421,346 patients) found both drug classes lowered death from any cause, heart-related death, heart attacks and kidney failure (high-certainty evidence). SGLT2 inhibitors prevented 3 to 40 deaths per 1,000 patients over 5 years, depending on risk, but caused genital infections. (Palmer et al., BMJ, 2021) [3]
GLP-1 drugs added to insulin may help some people with type 1 diabetes. Across 24 studies (3,377 patients), liraglutide reduced body weight and daily insulin needs without a significant rise in severe low blood sugar (OR 0.67), though nausea was much more likely (OR 6.5). (Park et al., J Clin Endocrinol Metab, 2024) [4]

Key takeaways

Diabetes medications lower blood sugar in different ways — some act on the liver, others on the pancreas, gut, kidneys or muscle. [1]
The three main groups are oral medications, non-insulin injectables and insulin. [1]
Type 1 diabetes always requires insulin; type 2 diabetes is treated with one or more medications chosen for each person. [1]
Insulin, meglitinides and sulfonylureas carry the highest risk of low blood sugar (below 70 mg/dL). [1]
Medications work best alongside glucose monitoring, meal planning, physical activity, and good sleep and stress control. [1]

The 3 main types of diabetes medications: oral pills, non-insulin injectables and insulin, with who each is for

What are the main types of diabetes medications?

The main types of diabetes medications are oral medications (pills), non-insulin injectable medications, and insulin. [1]

All three lower blood sugar (glucose), but each works differently. Some prompt the pancreas to release insulin. Others mimic natural hormones that help regulate blood sugar. [1]

Medication group	How you take it	Main action	Who it's for
Oral medications	Pills you swallow	Act on the liver, pancreas, gut, kidneys or muscle to lower glucose	Approved for type 2 diabetes; rarely used off-label in type 1
Non-insulin injectables	Shots (GLP-1 agonists, GLP-1/GIP receptor agonists)	Boost insulin release, slow digestion, reduce appetite	Approved for type 2 diabetes; sometimes used off-label in type 1
Insulin	Needle, pen, pump or inhaled	Replaces the natural hormone so cells can use glucose	Everyone with type 1; some people with type 2

Your treatment will not match a friend's or relative's. Your provider tailors medication choices to you. [1]

How do oral diabetes medications work?

Oral diabetes medications are pills that lower blood glucose through several different routes in the body. [1]

Drug class	How it lowers blood sugar
Biguanides (metformin)	Cut the amount of glucose the liver makes and releases. Metformin is the only biguanide.
Sulfonylureas	Trigger the pancreas to release insulin.
Meglitinides (glinides)	Trigger the pancreas to release insulin.
DPP-4 inhibitors (gliptins)	Keep the hormone GLP-1 active longer, which naturally lowers blood sugar.
GLP-1 agonist pill	Triggers insulin release, slows digestion and limits appetite. Oral semaglutide (Rybelsus) is currently the only GLP-1 pill approved for diabetes; orforglipron (Foundayo) is approved only for weight management.
SGLT2 inhibitors	Send extra glucose out of the body through urine.
Thiazolidinediones (TZDs)	Make muscle and fat tissue more sensitive to insulin.
Alpha-glucosidase inhibitors	Block the breakdown of starches and some sugars.
Dopamine-2 agonists	Help reverse insulin resistance and reduce liver glucose output.
Bile acid sequestrants (BASs)	Cholesterol-lowering drugs that also help lower blood glucose.

Each class has its own side effects, and some can interact with other medicines. For example, SGLT2 inhibitors can cause genital yeast infections and, rarely, ketoacidosis even when blood sugar is near normal, and metformin can rarely cause a dangerous buildup of lactic acid in people with poor kidney function. [1]

These pills are approved for people with type 2 diabetes. In rare cases, a provider may prescribe some of them off-label for type 1 diabetes. [1] If insulin resistance is part of your picture, our guide to insulin resistance explains why.

Where each oral diabetes medication class acts: liver, pancreas, gut, kidneys, muscle and fat, and bile acids

How do non-insulin injectable diabetes medications work?

Non-insulin injectable diabetes medications, such as GLP-1 agonists and GLP-1/GIP receptor agonists, make the pancreas release more insulin and slow digestion. [1]

Slower digestion helps reduce blood sugar spikes after meals. These drugs also increase fullness, which lowers appetite, hunger and food intake — so weight loss is common. GLP-1 drugs carry an FDA boxed warning about thyroid C-cell tumors, so they are not used by people with a personal or family history of medullary thyroid cancer or MEN 2, and severe belly pain can signal pancreatitis. [1]

They are approved for type 2 diabetes. Researchers are studying GLP-1 agonists in type 1 diabetes, and some providers already prescribe them off-label. [1][4] Learn more in our full guide to GLP-1 agonists.

How does insulin work as a diabetes medication?

Manufactured insulin works by mimicking the body's natural insulin, letting cells use glucose for energy and lowering the sugar in the blood. [1]

Insulin types differ in how quickly they start working and how long they last. Most are injected with a needle, pen or pump, and an inhaled form also exists. [1]

Type 1 diabetes: everyone needs insulin to live. [1]
Type 2 diabetes: some people need insulin to keep blood sugar in range. [1]

For a deeper look, read our guide to insulin and how it manages blood sugar.

How do doctors choose the right diabetes medication?

Doctors choose a diabetes medication by weighing how it works against your health, other medicines, side effects, low-blood-sugar risk, cost and personal goals. [1]

Published guidelines favor some drugs over others because of their added benefits. [1] Your provider considers:

How the medication works
Other health conditions you have
Possible interactions with your other medicines
Side effects
Risk of low blood sugar episodes
Insurance coverage and cost
Your preferences and health goals

You may start on one medication or a combination. Doses and drugs often change over time. [1]

Diabetes medications with higher low blood sugar risk and the seven factors doctors weigh when choosing treatment

What are the side effects and risks of diabetes medications?

The most common side effects of diabetes medications are digestive problems such as nausea, bloating and diarrhea, and the most serious risk is low blood sugar (hypoglycemia). [1]

Low blood sugar means a level below 70 mg/dL. It can happen if a dose is too high or you take more than prescribed. Treat it by eating or drinking sugar, as your provider explains. Untreated severe hypoglycemia can be life-threatening. [1]

Low blood sugar risk	Medications
Higher	Insulin, meglitinides, sulfonylureas
Varies by drug	Other classes — ask your provider about your specific medicine

Know the warning signs and how to respond: see our guide to diabetic hypoglycemia and fast treatment.

What are the most effective diabetes medications?

Insulin is the most potent diabetes medication because it lowers blood glucose the most. [1]

Metformin is the most commonly used medication for type 2 diabetes. It is often effective and has fewer side effects than other options. [1]
GLP-1 drugs such as tirzepatide and semaglutide are also very effective at lowering A1C. [1]

Effectiveness is usually measured by how much a drug lowers your A1C — your average blood sugar over about three months. [1] But the "best" drug for you may differ. You may want to avoid low blood sugar or certain side effects, or another condition may rule some medicines out. [1]

How long do you need to take diabetes medications?

How long you need diabetes medications depends on the type of diabetes: type 1 requires insulin for life, while type 2 needs long-term management that may or may not include medication. [1]

Some people with type 2 diabetes stop medication when steady food changes and physical activity keep their glucose in range. Diabetes also tends to progress, so needing more medication over time is common — even with healthy habits. [1]

Never stop a diabetes medication without talking to your provider first. [1]

Can type 2 diabetes be managed without medication?

Some people with type 2 diabetes — not everyone — can manage it without medication through changes in eating and activity, plus weight loss if they have overweight or obesity. [1]

Type 1 diabetes always requires insulin. [1]

Be careful with products claiming to prevent, treat or cure diabetes. The U.S. Food and Drug Administration advises avoiding them. Only take prescription drugs, over-the-counter medicines and supplements your provider approves. [1]

What helps diabetes medications work better?

Diabetes medications work better when combined with glucose monitoring, meal planning, physical activity, and stress and sleep management. [1]

Strategy	Why it matters
Glucose monitoring	Checking before and after meals and exercise shows their effect and whether your plan is working.
Meal planning	What you eat affects blood glucose on any medication. A registered dietitian can help.
Physical activity	Helps the body use insulin better and lowers blood sugar; plan it around your medication.
Stress and sleep	Lower stress and quality sleep help keep glucose in range.

Finding the right medication or combination can take weeks or months, and your plan will change as your body and routine change. [1]

When should you call your doctor about diabetes medications?

You should call your doctor about diabetes medications if you have bothersome side effects, frequent or severe low blood sugar, or significant weight changes. [1]

Regular visits matter too. Your provider will order tests such as an A1C to check how treatment is working. Some drugs need routine blood tests — for example, metformin users have vitamin B12 and kidney function checked. [1] Good control helps prevent complications such as kidney disease, eye damage and nerve damage. [1][3]

Seek emergency care for severe low blood sugar symptoms such as confusion or loss of consciousness, or signs of diabetic ketoacidosis (DKA).

Conclusion

There is no single "best" diabetes medication. Pills, non-insulin injectables and insulin each lower blood sugar in different ways, and the right choice depends on your type of diabetes, health conditions, side effects and goals. [1] Strong evidence shows some newer drugs also protect the heart and kidneys. [3] Whatever you take, medication works best alongside monitoring, healthy eating, activity and good sleep.

Next step: Bring this guide to your next appointment and ask your provider which medication fits your goals. Then explore our complete diabetes guide to understand every part of managing the condition.

FAQ

What are the three main types of diabetes medications?

The three main types are oral medications (pills), non-insulin injectable medications such as GLP-1 agonists, and insulin. Each group lowers blood sugar in a different way.

What is the most common medication for type 2 diabetes?

Metformin is the most common medication for type 2 diabetes. It is often effective and has fewer side effects than many other options.

Which diabetes medications cause low blood sugar?

Insulin, meglitinides and sulfonylureas are the diabetes medications most likely to cause low blood sugar. A level below 70 mg/dL needs prompt treatment with sugar.

Do people with type 1 diabetes need insulin?

Yes. Everyone with type 1 diabetes needs insulin to live. Some providers also add other drugs off-label, such as GLP-1 agonists.

What are the common side effects of diabetes medications?

Common side effects include digestive issues such as nausea, bloating and diarrhea. Each medication has its own side effects, so ask your provider what to watch for.

Can I stop taking my diabetes medication?

Talk to your healthcare provider before stopping any diabetes medication. Some people with type 2 diabetes can come off medication if diet and activity keep glucose in range, but type 1 diabetes always needs insulin.

How long does it take for diabetes medication to work?

Finding the medication or combination that works best can take weeks or months. Your provider will adjust your plan as your body or routine changes.

What is the most effective diabetes medication?

Insulin lowers blood glucose the most. Metformin and GLP-1 drugs such as semaglutide and tirzepatide are also very effective at lowering A1C.

Can diabetes medications cause weight gain?

Some can. Insulin, sulfonylureas and thiazolidinediones may cause weight gain, while GLP-1 receptor agonists and SGLT2 inhibitors often help with weight loss. Metformin usually does not cause weight gain.

What should I do if I miss a dose of my diabetes medicine?

Check your medicine's label or ask your pharmacist, because the advice differs by drug. Do not take a double dose to make up for a missed one unless your provider tells you to.

References

Cleveland Clinic. Common Types of Diabetes Medications. Cleveland Clinic. Last updated March 11, 2026. https://my.clevelandclinic.org/health/treatments/diabetes-medications
GRADE Study Research Group; Nathan DM, Lachin JM, Balasubramanyam A, et al. Glycemia Reduction in Type 2 Diabetes - Glycemic Outcomes. N Engl J Med. 2022;387(12):1063-1074. PMID 36129996. https://doi.org/10.1056/NEJMoa2200433
Palmer SC, Tendal B, Mustafa RA, et al. Sodium-glucose cotransporter protein-2 (SGLT-2) inhibitors and glucagon-like peptide-1 (GLP-1) receptor agonists for type 2 diabetes: systematic review and network meta-analysis of randomised controlled trials. BMJ. 2021;372:m4573. PMID 33441402. https://doi.org/10.1136/bmj.m4573
Park J, Ntelis S, Yunasan E, et al. Glucagon-Like Peptide 1 Analogues as Adjunctive Therapy for Patients With Type 1 Diabetes: An Updated Systematic Review and Meta-analysis. J Clin Endocrinol Metab. 2024;109(1):279-292. PMID 37561012. https://doi.org/10.1210/clinem/dgad471

Medical disclaimer

This article is for general educational purposes only and is not a substitute for professional medical advice, diagnosis or treatment. Do not start, stop or change any diabetes medication without talking to your healthcare provider. If you think you are having a medical emergency, call your local emergency number right away.