Humulin R (insulin human) is a prescription drug used to help manage blood sugar levels in people with diabetes. It can interact with alcohol, some supplements, and other medications. An example is birth control pills.
Humulin R helps manage blood sugar in adults and children with type 1 diabetes or type 2 diabetes.
The active ingredient in Humulin R is insulin human.
Humulin R is available in a liquid solution in two forms. (Unless otherwise noted, this article uses “Humulin R” to describe both forms.) The forms are:
- Humulin R U-100: for injection under your skin or intravenous (IV) infusion (an injection given into your vein over a period of time)
- Humulin R U-500: for injection under your skin
An interaction can occur because one substance causes another substance to have a different effect than expected. Interactions also can occur if you have certain health conditions.
Keep reading to learn about Humulin R’s possible interactions. And for more information about Humulin R, including details about its uses, see this article.
Note: Humulin R U-100 is also available over the counter (OTC) without a prescription.
Before you start using Humulin R, tell your doctor and pharmacist about any prescription, OTC, or other drugs you take. Sharing this information with them may help prevent possible interactions. (To learn whether Humulin R interacts with herbs or vitamins and supplements, see the “Are there other interactions with Humulin R?” section below.)
If you have questions about drug interactions that may affect you, talk with your doctor or pharmacist.
The table below lists drugs that may interact with Humulin R. Keep in mind that this table does not include all drugs that may interact with Humulin R. For more information about some of these interactions, see the “Drug interactions explained” section below.
| Drug group or drug name | Drug examples | What can happen |
| beta-blockers | • atenolol (Tenormin) • bisoprolol • propranolol (Hemangeol, Inderal LA, others) | can hide symptoms of low blood sugar or affect how well blood sugar is managed |
| thiazolidinediones | • pioglitazone (Actos) | can increase the risk of low blood sugar or water retention |
| thyroid hormone drugs | • levothyroxine (Unithroid, Synthroid, others) • liothyronine (Cytomel) • desiccated thyroid (Armour Thyroid) | can make Humulin R less effective |
| angiotensin converting enzyme (ACE) inhibitors | • lisinopril (Qbrelis, Zestril) • quinapril • ramipril (Altace) | can increase the risk of low blood sugar |
| birth control pills | • ethinyl estradiol/norethindrone (Gildess, Junel, others) • ethinyl estradiol/norgestimate (Estarylla, Sprintec, others) • ethinyl estradiol/drospirenone (Yasmin, Yaz, others) | can make Humulin R less effective |
| certain antipsychotic drugs | • brexpiprazole (Rexulti) • clozapine (Clozaril, Versacloz) • olanzapine (Zyprexa) | can make Humulin R less effective |
| lithium (Lithobid) | — | can affect how well blood sugar is managed |
| clonidine (Catapres, Nexiclon XR, others) | — | can hide symptoms of low blood sugar or affect how well blood sugar is managed |
| aspirin | — | can increase the risk of low blood sugar |
| fluoxetine (Prozac) | — | can increase the risk of low blood sugar |
Certain health conditions or other factors could raise your risk of harm if you use Humulin R. In such cases, your doctor may not prescribe Humulin R for you. These are known as contraindications. The list below includes Humulin R contraindications.
- If you’re having an episode of low blood sugar: If you’re having an episode of low blood sugar, you should not use Humulin R. This is because Humulin R lowers blood sugar. Using Humulin R during this time could cause your blood sugar to become dangerously low. Ask your doctor when it’s safe to resume Humulin R after an episode of low blood sugar.
- If you’ve had an allergic reaction: If you’ve had an allergic reaction to Humulin R or any of its ingredients, your doctor likely will not prescribe Humulin R for you. This is because using the drug could cause another allergic reaction. You can ask your doctor about other treatments that may be better options for you.
Before you start using Humulin R, talk with your doctor if any of the factors above apply to you. Your doctor can determine whether Humulin R is safe for you to use.
It may not be safe to consume alcohol while you’re using Humulin R. This is because alcohol can increase or decrease your blood sugar. As a result, drinking alcohol can make it difficult to manage your blood sugar while using Humulin R.
For this reason, your doctor may recommend that you avoid consuming alcohol while you’re using Humulin R.
If you have questions about consuming alcohol during Humulin R treatment, talk with your doctor or pharmacist.
Learn more about certain drug interactions that can occur with Humulin R.
Interaction with thyroid hormone drugs
Humulin R can interact with thyroid hormone drugs, which are used to treat thyroid conditions.
Examples of thyroid hormone medications include:
- levothyroxine (Unithroid, Synthroid, others)
- liothyronine (Cytomel)
- desiccated thyroid (Armour Thyroid)
What could happen
Using Humulin R while taking a thyroid hormone drug could make Humulin R less effective.
Humulin R is used to manage blood sugar in people with diabetes. Thyroid hormones also play a role in managing blood sugar, which thyroid hormone drugs may help. Starting or stopping thyroid hormone drugs during Humulin R treatment could affect how well Humulin R works.
What you can do
If you use Humulin R with a thyroid hormone drug, your doctor may adjust your Humulin R dosage. They’ll recommend a dosage that helps you maintain a healthy blood sugar range.
If you have questions about using Humulin R along with a thyroid hormone drug, talk with your doctor or pharmacist.
Interaction with birth control pills
Humulin R can interact with birth control pills, which are used to prevent pregnancy.
Examples of birth control pills include:
- ethinyl estradiol/norethindrone (Gildess, Junel, others)
- ethinyl estradiol/norgestimate (Estarylla, Sprintec, others)
- ethinyl estradiol/drospirenone (Yasmin, Yaz, others)
What could happen
Taking birth control pills while using Humulin R could make Humulin R less effective.
The hormones in birth control pills may affect blood sugar. And Humulin R is used to manage blood sugar in people with diabetes. So starting or stopping birth control pills while using Humulin R could affect how well Humulin R works.
What you can do
If you take birth control pills while using Humulin R, your doctor may adjust your Humulin R dosage. They’ll prescribe the dosage that helps you maintain a healthy blood sugar range.
If you have questions about using Humulin R along with birth control pills, talk with your doctor or pharmacist.
Interaction with aspirin
Humulin R can interact with aspirin. Among other uses, aspirin may ease pain and lower the risk of a heart attack.
What could happen
Humulin R is used to lower blood sugar in people with diabetes. Aspirin may cause low blood sugar in people with diabetes. So taking these drugs together can raise your risk of low blood sugar.
What you can do
If you use Humulin R with aspirin, your doctor may suggest checking your blood sugar more often than usual. They’ll recommend a healthy blood sugar range for you. Your doctor can also advise what to do if your blood sugar falls below this range.
If you have questions about using Humulin R while taking aspirin, talk with your doctor or pharmacist.
Humulin R may have other interactions. They could occur with supplements, foods, vaccines, or even lab tests. See below for details. Note that the information below does not include all other interactions possible with Humulin R.
Does Humulin R interact with supplements?
Humulin R can interact with garlic supplements, which may be used to manage blood sugar levels. (Humulin R also is used for this purpose.)
Using Humulin R while taking a garlic supplement could increase your risk of low blood sugar. Your doctor can recommend whether it’s safe to take garlic supplements while you’re using Humulin R.
Before you start using Humulin R, talk with your doctor and pharmacist about any herbs or vitamins and supplements you take. Sharing this information with them may help you avoid possible interactions.
If you have questions about interactions that may affect you, talk with your doctor or pharmacist.
Humulin R and herbs
Humulin R U-100 and Humulin R U-500 currently have no reports of interacting with herbs. But this doesn’t mean that interactions with herbs won’t be recognized in the future.
For this reason, it’s still important to check with your doctor or pharmacist before taking any of these products while using Humulin R.
Humulin R interactions with vitamins or minerals
Humulin R can interact with chromium, which may be used to manage blood sugar levels. (Humulin R also is used for this purpose.) Using Humulin R while taking chromium could increase your risk of low blood sugar.
Your doctor can recommend whether it’s safe to take any vitamins or minerals while you’re using Humulin R.
Does Humulin R interact with food?
Humulin R can interact with green tea, which may help manage blood sugar levels. (Humulin R also is used for this purpose.) Consuming green tea with Humulin R could increase your risk of low blood sugar.
Although garlic supplements may interact with Humulin R, it should be safe to consume garlic in foods or seasonings. (See “Does Humulin R interact with supplements?” above for information on garlic supplements.) The amount of garlic in foods or seasonings typically is much lower than what’s in a garlic supplement.
If you have additional questions about eating certain foods while using Humulin R, talk with your doctor.
Does Humulin R interact with vaccines?
Humulin R U-100 and Humulin R U-500 currently have no reports of interacting with vaccines. If you have questions about getting certain vaccines during your Humulin R treatment, talk with your doctor.
Does Humulin R interact with lab tests?
Humulin R U-100 and Humulin R U-500 currently have no reports of interacting with lab tests. If you have questions about having certain lab tests during your treatment with Humulin R, talk with the healthcare professional ordering the test.
Does Humulin R interact with cannabis or CBD?Humulin R U-100 and Humulin R U-500 aren’t known to interact with cannabis or cannabis products such as cannabidiol (CBD). (Cannabis is commonly called marijuana.) But as with any drug or supplement, talk with your doctor before using cannabis with Humulin R.
Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
Certain medical conditions or other health factors may raise the risk of interactions with Humulin R. Before using Humulin R, talk with your doctor about your health history. They’ll determine whether Humulin R is right for you.
Health conditions or other factors that might interact with Humulin R include:
Low blood potassium: Humulin R can cause a low blood potassium level. If you already have this condition, using Humulin R could worsen it. A very low blood potassium level can be life threatening.
Your doctor may check your potassium level from time to time during Humulin R treatment.
Low blood sugar: You should not use Humulin R during an episode of low blood sugar. For details, see the “When should I avoid Humulin R?” section above.
Pregnancy: Humulin R is usually considered safe to use during pregnancy. If you’re pregnant or planning a pregnancy, let your doctor know before using Humulin R.
Breastfeeding: It’s usually considered safe to use Humulin R while breastfeeding. If you’re breastfeeding or planning to breastfeed, let your doctor know before using Humulin R.
Allergic reaction: If you’ve had an allergic reaction to Humulin R or any of its ingredients, your doctor likely will not prescribe Humulin R. This is because using the drug could cause another allergic reaction. You can ask your doctor about other treatments that may be better choices for you.
Taking certain steps can help you avoid interactions with Humulin R. Before starting treatment, talk with your doctor and pharmacist. Things to discuss with them include:
- whether you drink alcohol or use cannabis
- other medications you take, as well as any vitamins, supplements, and herbs (they can also help you fill out a medication list)
- what to do if you start taking a new drug during your Humulin R treatment
It’s also important to understand Humulin R’s
If you have difficulty reading or understanding this information, your doctor or pharmacist can help.
Using Humulin R exactly as prescribed can also help prevent interactions.
Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.