Can Zyrtec Raise Blood Sugar? A Look at Antihistamines and Glucose Control

October 7, 2025 •

4 min read

According to diabetes health resources and medical experts, oral antihistamines like Zyrtec (cetirizine) typically have minimal to no effect on blood sugar levels for most individuals. However, understanding the specific formulation, potential for indirect effects, and differences between allergy medications is crucial when considering if Zyrtec can raise blood sugar.

Quick Summary

Zyrtec (cetirizine) does not directly raise blood sugar for most people with diabetes. Special attention is needed for combination products with decongestants (like Zyrtec-D), liquid formulations with added sugar, and the overall effect of illness or drowsiness on glucose management.

Key Points

Standard Zyrtec (Cetirizine) is Generally Safe: Oral Zyrtec tablets do not typically raise blood sugar levels and are considered a safe option for most individuals with diabetes.
Zyrtec-D Contains a Decongestant that Raises Blood Sugar: The pseudoephedrine in Zyrtec-D can elevate blood sugar by releasing stress hormones and should be used cautiously by people with diabetes.
Illness Itself Can Increase Blood Sugar: An underlying illness or allergic reaction can trigger stress hormones that naturally cause glucose levels to rise, independent of the antihistamine.
Liquid Versions May Contain Sugar: Zyrtec syrups often have added sugar. Diabetics should read labels and consider sugar-free alternatives or tablet/capsule forms.
Drowsiness Can Mask Symptoms: The sedative effect of some antihistamines can make it harder to recognize the symptoms of high or low blood sugar.
Always Consult a Healthcare Provider: It is crucial for people with diabetes to speak to a doctor or pharmacist before starting any new medication, even an over-the-counter one.
Consider Non-Drowsy, Non-Combination Options: For safest use, diabetics should look for plain, non-drowsy antihistamines in tablet or capsule form.

How Standard Zyrtec (Cetirizine) Impacts Blood Sugar

Zyrtec, whose active ingredient is cetirizine, is a second-generation antihistamine. Its primary function is to block the body's histamine response, which is responsible for common allergy symptoms like sneezing, itching, and a runny nose. Unlike some other medications, cetirizine is not known to directly interfere with insulin sensitivity or glucose metabolism in a way that significantly elevates blood sugar. For this reason, standard Zyrtec tablets or capsules are considered a safe option for managing allergy symptoms in individuals with diabetes. A key consideration, however, is the potential for drowsiness, especially in older adults. This sedation could inadvertently cause a person to miss or misinterpret signs of a hypoglycemic or hyperglycemic event. Non-drowsy formulations are often recommended for those concerned about this side effect.

The Critical Difference: Zyrtec-D and Decongestants

The most important distinction for people with diabetes is understanding the difference between standard Zyrtec and combination products like Zyrtec-D. The "D" in Zyrtec-D stands for decongestant, which is pseudoephedrine. Pseudoephedrine is a stimulant that can significantly impact blood sugar levels.

Mechanism of action: Decongestants like pseudoephedrine work by stimulating the body's nervous system, leading to the release of stress hormones, including epinephrine (adrenaline).
Epinephrine's effect on glucose: Epinephrine triggers the liver to produce more glucose and can reduce the body's sensitivity to insulin. This can cause a noticeable and potentially dangerous spike in blood sugar.
Recommendation for diabetics: Individuals with diabetes, especially those with pre-existing heart disease or high blood pressure, are generally advised to use decongestants with extreme caution. Close monitoring of blood sugar is essential, and a doctor should be consulted before use.

The Impact of Illness, Syrups, and Other Allergy Medications

Several factors besides the active ingredient can influence glucose levels. It is important for individuals with diabetes to be aware of these when managing allergies or a cold:

Illness-related stress: Any infection or sickness, including severe allergies, can cause the body to release stress hormones. This natural response helps the body fight off illness but also raises blood sugar levels. This effect, not the antihistamine itself, is often the cause of a high reading during a period of illness.
Liquid formulations: Liquid Zyrtec syrups often contain added sugar to make them more palatable. While the total sugar amount is typically small, it's an unnecessary variable for someone managing diabetes. Tablets or capsules are usually a safer, sugar-free alternative. Always read the label to check for added sugars or alcohol.
Corticosteroids: Another common type of allergy medication, corticosteroids (like prednisone) are well-known to cause significant increases in blood sugar and insulin resistance, and they should only be used under a doctor's strict supervision for people with diabetes. Some intranasal corticosteroids have been shown to have less impact, but oral steroids are a major concern.

Comparison of Allergy Medications for Diabetics


Medication Type	Primary Active Ingredient	Effect on Blood Sugar	Key Consideration for Diabetics
Standard Zyrtec	Cetirizine (antihistamine)	Minimal to no effect	Generally safe; choose non-drowsy options if concerned about masking symptoms.
Zyrtec-D	Cetirizine + Pseudoephedrine (decongestant)	Pseudoephedrine can significantly raise blood sugar.	Use with extreme caution and monitor blood sugar closely.
First-Generation Antihistamines	Diphenhydramine (e.g., Benadryl)	Minimal direct effect, but significant drowsiness.	High potential for drowsiness makes it difficult to recognize hypo/hyperglycemia symptoms.
Liquid Syrups	Various (includes Zyrtec)	May contain added sugar.	Check labels and prefer sugar-free tablet/capsule options.
Oral Corticosteroids	Prednisone, etc.	Significantly raises blood sugar and insulin resistance.	Only use if medically necessary and under close supervision.

Best Practices for Diabetics Taking Zyrtec

If you have diabetes and plan to take an allergy medication, following these steps can help you manage your glucose levels effectively:

Talk to your doctor or pharmacist: Before starting any new over-the-counter or prescription medication, discuss it with your healthcare provider. This is especially important for those with diabetes, heart disease, or high blood pressure.
Read the label carefully: Always check for combination products, like Zyrtec-D, which include decongestants. Also, review the ingredients list on liquid versions for hidden sugars or alcohol.
Monitor blood sugar frequently: When starting a new medication or during an illness, increase the frequency of your blood sugar testing. This helps you identify any unusual patterns or unexpected spikes.
Opt for non-drowsy options: If you are sensitive to drowsiness, choose a non-sedating antihistamine. This allows you to stay alert and better recognize potential signs of high or low blood sugar.

Conclusion: The Verdict on Zyrtec and Blood Sugar

For most people with diabetes, standard Zyrtec (cetirizine) does not directly raise blood sugar levels and is generally a safe and effective option for allergy relief. However, the situation becomes more complex with specific formulations and compounding factors. Combination products like Zyrtec-D, which contain the decongestant pseudoephedrine, can cause blood sugar to rise and should be used with caution. Additionally, the sugar content in liquid syrups and the body's natural stress response to illness are important considerations. The best approach is to always communicate with a healthcare professional, carefully read medication labels, and monitor blood sugar consistently to ensure effective and safe allergy management.

DiaTribe.org is an excellent resource for managing diabetes and allergies.

Frequently Asked Questions

No, standard Zyrtec (cetirizine) is a second-generation antihistamine and does not typically raise blood sugar levels in most people. It is generally considered a safe option for allergy relief for individuals with diabetes.

Zyrtec-D contains the decongestant pseudoephedrine, in addition to the antihistamine cetirizine. Pseudoephedrine is a stimulant that can trigger the release of stress hormones, which can cause blood sugar levels to rise.

It is often the illness itself that causes blood sugar to rise, not the Zyrtec. When you are sick, your body releases stress hormones that can naturally increase your glucose levels.

Not all liquid allergy medicines contain sugar, but many do. Some formulations use sugar to improve the taste. If you have diabetes, it is best to read the label carefully or choose a sugar-free alternative, such as a tablet or capsule.

The drowsiness caused by some antihistamine formulations can mask the symptoms of both high and low blood sugar. This makes it more difficult to recognize when your glucose levels are out of range.

For most people with diabetes, a non-drowsy, second-generation antihistamine like standard Zyrtec or Claritin is a safe choice. Avoid combination products containing decongestants and read labels on liquid medicines for added sugar.

If your blood sugar rises after taking Zyrtec, it is likely due to the illness causing your allergies rather than the medication itself. Increased blood sugar monitoring is recommended during illness, and you should consult your doctor if levels remain consistently high.

Older, first-generation antihistamines like Benadryl (diphenhydramine) do not typically raise blood sugar directly, but they can cause significant drowsiness. The sedation can make it harder to manage diabetes, so newer, non-drowsy options are often preferred.