Short answer: The Micardis HCT label names upper respiratory infection, dizziness, sinusitis, diarrhea, fatigue, flu-like symptoms and nausea as the most common side effects (2% or more). In trials, dizziness was 5% vs 1% on placebo and upper respiratory infection 8% vs 7%. Warnings cover low blood pressure, kidney and salt changes, and sudden eye pressure. It has a boxed warning for harm to an unborn baby.
What Micardis HCT is approved for: Micardis HCT combines telmisartan, an angiotensin II receptor blocker (ARB), with hydrochlorothiazide, a thiazide diuretic. It is approved to treat high blood pressure, alone or with other blood pressure medicines. It is not approved as the first treatment for high blood pressure; it is used when telmisartan or hydrochlorothiazide alone has not been enough. The label says there are no controlled trials showing risk reduction with Micardis HCT itself (section 1).
Source
MICARDIS HCT (telmisartan and hydrochlorothiazide tablets), for oral use, prescribing information and Patient Information. Boehringer Ingelheim. DailyMed, version published March 27, 2025. DailyMed setid b078dae2-664d-4144-847a-3b9d9b557402
WARNING: FETAL TOXICITY
When pregnancy is detected, discontinue MICARDIS HCT as soon as possible. Drugs that act directly on the renin-angiotensin system can cause injury and death to the developing fetus (Boxed Warning; sections 5.1 and 8.1).
These are the label's own numbers from the Adverse Reactions section. Where the label compares with placebo (a dummy treatment), both columns are shown, so you can see how much more often a reaction happened on Micardis HCT.
| Adverse reaction | Telmisartan/HCTZ (n=414) | Placebo (n=74) | Telmisartan (n=209) | Hydrochlorothiazide (n=121) |
|---|---|---|---|---|
| Fatigue | 3% | 1% | 3% | 3% |
| Influenza-like symptoms | 2% | 1% | 2% | 3% |
| Dizziness | 5% | 1% | 4% | 6% |
| Diarrhea | 3% | 0% | 5% | 2% |
| Nausea | 2% | 0% | 1% | 2% |
| Sinusitis | 4% | 3% | 3% | 6% |
| Upper respiratory tract infection | 8% | 7% | 7% | 10% |
The label notes the groups include all doses of telmisartan (20 to 160 mg), hydrochlorothiazide (6.25 to 25 mg) and their combinations. Other reactions seen on the combination: pain (including back and abdominal), dyspepsia, erythema, vomiting, bronchitis and pharyngitis.
Increases in blood urea nitrogen (11.2 mg/dL or more) and creatinine (0.5 mg/dL or more) were seen in 2.8% and 1.4% of people on Micardis HCT in controlled trials. No one stopped because of them.
In controlled trials of the 40/12.5, 80/12.5 and 80/25 mg doses, no one had a potassium drop of 1.4 mEq/L or more, and no one had high potassium.
Side effects occurred at about the same rates in men and women, older and younger people, and Black and non-Black people.
Hydrochlorothiazide is linked with a higher risk of non-melanoma skin cancer, mainly squamous cell carcinoma: about 1 extra case per 16,000 people per year overall, and about 1 per 6,700 per year in white people with a cumulative dose of 50,000 mg or more.
Reported after approval include angioedema (including with fatal outcome), anaphylactic reaction, fainting, low blood pressure on standing, kidney failure, low sodium, low blood sugar in people with diabetes, rhabdomyolysis, erectile dysfunction, cough and abnormal liver function.
The Warnings and Precautions part of the label lists these. Each line gives the label's heading and what it means in plain words.
Who should not take it. People allergic to any ingredient, people with anuria (no urine output), and people with diabetes who take aliskiren.
Fetal toxicity. Medicines acting on the renin-angiotensin system in the second and third trimesters reduce the baby's kidney function and raise the risk of harm and death to the fetus and newborn. Thiazides cross the placenta and can cause jaundice and low platelets in the baby. Micardis HCT is stopped as soon as pregnancy is detected.
Low blood pressure in people low on fluid or salt. Low blood pressure with symptoms can happen after starting, for example in people on high-dose diuretics. Fluid or salt loss is corrected before starting.
Kidney function. Kidney changes, including acute kidney failure, can occur, especially with renal artery stenosis, chronic kidney disease, severe heart failure or fluid loss. Kidney function is checked periodically, and treatment may be held or stopped if it drops meaningfully.
Salt, potassium and metabolic changes. Telmisartan can raise potassium; hydrochlorothiazide can lower potassium, sodium and magnesium, raise calcium, blood sugar, cholesterol and triglycerides, and raise uric acid or bring on gout. Electrolytes are checked periodically.
Allergic reactions. Reactions to hydrochlorothiazide can occur with or without a history of allergy or asthma, but are more likely with one.
Sudden nearsightedness and angle-closure glaucoma. Hydrochlorothiazide can cause sudden blurred vision or eye pain within hours to weeks of starting. Untreated, angle-closure glaucoma can cause permanent vision loss. Hydrochlorothiazide is stopped as fast as possible. A history of sulfonamide or penicillin allergy may raise the risk.
Lupus. Thiazide diuretics have been reported to worsen or activate systemic lupus erythematosus.
Drug interactions. Other potassium-raising drugs, lithium (toxicity), NSAIDs (kidney harm and weaker effect), other RAS blockers or aliskiren, digoxin (higher levels), diabetes medicines (doses may need changing) and cholestyramine or colestipol (less hydrochlorothiazide absorbed).
Severe liver or kidney impairment. Micardis HCT is not recommended in severe liver impairment or severe kidney impairment (creatinine clearance 30 mL/min or less).
From the Patient Information that comes with Micardis HCT:
Dose Track has a side-effect log. Each entry records the symptom, a severity (none, mild, moderate, severe or life-threatening), the date and an optional note, and can be tied to a specific dose or logged on its own. The history screen shows what you logged over time, which makes it easier to tell your prescriber when a reaction started and whether it is easing. The app records what you enter; it does not judge whether a symptom is serious. For anything on the label's call-your-doctor list, call your doctor.
This page is what the FDA label says, in plain words. It is not medical advice. Follow your prescriber, and ask them or your pharmacist about anything here.