Enclomiphene is generally reported as well tolerated in the small studies done so far. The effects most often described are headache, hot flashes, fatigue, lower libido and mood changes. But it is not an FDA-approved drug, and its long-term safety has not been fully established. In a 2024 retrospective study of 66 men, adverse effects were documented in 13.8% of men taking enclomiphene and 47% of men taking clomiphene. That is useful, but it is a small, non-randomized comparison, not proof that one drug is safer for you.
This guide goes through what has been reported, what is unknown, how enclomiphene compares with clomiphene (Clomid) and testosterone replacement therapy (TRT), and what to bring to a clinician visit.
TL;DR
- Reported enclomiphene side effects are usually mild: headache, hot flashes, gastrointestinal upset, fatigue, lower libido and mood changes. Rates vary by study and the studies are small.
- In one retrospective study of 66 men, adverse effects were less frequent with enclomiphene (13.8%) than clomiphene (47%). Retrospective data cannot prove cause.
- Enclomiphene is not FDA-approved. It is on the FDA's list of bulk substances under evaluation for compounding, which is not an approval.
- Compared with TRT, enclomiphene aims to raise your own testosterone and keep sperm production going, but long-term data are thin.
- New vision changes, chest pain, a swollen painful leg or sudden shortness of breath need urgent medical care, not a wait-and-see approach.
Table of Contents
- What enclomiphene is and why side effects are hard to pin down
- Enclomiphene side effects reported in studies
- Which side effects could be serious?
- Is enclomiphene safe? What the evidence can and cannot say
- Enclomiphene vs. clomiphene (Clomid)
- Enclomiphene vs. TRT: risks and trade-offs
- Who should be especially careful
- How to prepare for a clinician visit
- Understanding the FDA's compounding category
- Our perspective
- Talk to a clinician before you decide
- FAQ
- Sources
What enclomiphene is and why side effects are hard to pin down
Enclomiphene is one of the two isomers that make up clomiphene citrate. It blocks estrogen receptors in the brain, which signals the pituitary to release more luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In men with low testosterone caused by a signaling problem (secondary or central hypogonadism), that can raise the testicles' own testosterone output. Because it works upstream, it is sometimes discussed for men who want to keep fertility.
Two facts shape every safety discussion:
- It is not an FDA-approved medication in the US. According to a 2025 review of fertility preservation in testosterone deficiency, the developer discontinued clinical investigation in 2021 after the FDA requested additional trials. The same review notes it remains available through compounding pharmacies with a prescription, and that its long-term safety profile and effect on fertility outcomes have not been fully validated.
- Most human data are short and small. Trials run for months, not decades, and the real-world studies are retrospective.
So "side effects" here means what was recorded in limited groups of men, not a complete safety label. There is no FDA prescribing information for enclomiphene to consult.
Enclomiphene side effects reported in studies
The best-organized recent real-world comparison is a retrospective study of 66 men published in 2024 that looked at enclomiphene and clomiphene for low testosterone. Among men taking enclomiphene, adverse effects were reported in 13.8%. Specific items included decreased libido (8.6%), reduced energy (5.2%) and mood changes (0%).
Other side effects that clinicians and trial reports commonly list for enclomiphene and closely related drugs include:
| Effect | What patients may notice | Notes |
|---|---|---|
| Headache | Mild to moderate, often early in treatment | Among the most frequently listed effects |
| Hot flashes | Sudden warmth, sweating | Linked to estrogen-receptor blocking |
| Gastrointestinal upset | Nausea, loose stools | Usually mild |
| Fatigue or low energy | Reduced drive | Can also be a sign testosterone is not rising enough |
| Lower libido | Reduced sexual interest | Reported in the 2024 study above |
| Dizziness, muscle spasms | Occasional | Reported in trial summaries |
| Acne, breast tenderness | Hormone-related | Less well documented |
Two cautions about this list. First, symptoms like fatigue and low libido are also symptoms of the condition being treated, so it can be hard to tell a side effect from untreated low testosterone. Second, percentages from different studies cannot be stacked side by side: they differ in dose, length, who was enrolled and how adverse events were recorded.
Hormone changes that are not symptoms
Enclomiphene raises LH, FSH, total testosterone and usually estradiol. Higher estradiol is an expected result of more testosterone being made, not necessarily a problem, but a clinician will usually check it. A 2016 Journal of Urology abstract comparing oral enclomiphene with testosterone gel found more significant and sustained increases in total testosterone and estradiol with enclomiphene, along with larger drops in cholesterol. If you have symptoms like breast tenderness or mood swings, bring recent lab results so the conversation can be about numbers and timing, not guesses. For background on how estrogen relates to mood, this explainer on estrogen and mood across life stages is a helpful companion read.
Which side effects could be serious?
No large trial has defined serious risks for enclomiphene specifically, and we are not going to guess at rates. What a careful clinician does is borrow caution from the parent drug and from general medical sense. Clomiphene citrate's labeling includes warnings about visual symptoms such as blurring, spots or flashes, so a patient on any drug in this family who notices a new change in vision should stop and call a clinician promptly.
Contact a clinician the same day, or emergency services when symptoms are severe, for:
- New blurred vision, spots, flashes or other visual changes
- Chest pain, sudden shortness of breath or coughing up blood
- A swollen, warm, painful calf or thigh
- Sudden severe headache, weakness on one side, or trouble speaking
- Severe mood changes, including thoughts of self-harm (in the US you can call or text 988)
These are general warning signs for any medicine that alters hormones, not a statement that enclomiphene is known to cause them at a particular rate. Do not stretch out an uncomfortable symptom to "see if it passes." Tell the prescriber, and bring the pharmacy label so they know exactly what you are taking.
Is enclomiphene safe? What the evidence can and cannot say
The honest answer is that it looks tolerable in short-term studies, and that is not the same as established safety.
What supports cautious optimism
- In the 66-man retrospective comparison, adverse effects were documented less often with enclomiphene than with clomiphene.
- In the 2016 comparison with testosterone gels, hemoglobin and hematocrit were higher with the gels and no erythrocytosis was reported in the enclomiphene groups.
- Enclomiphene is designed to stimulate natural production and maintain spermatogenesis, as the 2025 fertility review describes.
What limits confidence
- No FDA approval and no completed phase 3 program. The developer stopped investigation in 2021.
- Retrospective designs, small samples and short follow-up.
- Compounded products are not FDA-approved drugs and are not reviewed by the FDA for safety, effectiveness or quality before they are sold.
Anyone who tells you enclomiphene has "no side effects" is going beyond the evidence. A better framing is: low rates of mostly mild effects in limited data, with unknowns about years of use.
Enclomiphene vs. clomiphene (Clomid)
Clomiphene citrate is a mix of two isomers: enclomiphene (the trans isomer) and zuclomiphene (the cis isomer). Zuclomiphene has a much longer half-life and is estrogen-like, and it is often blamed for the mood, visual and estrogenic effects seen with clomiphene. That is a reasoned explanation, though not something every study has proved.
| Enclomiphene | Clomiphene (Clomid) | |
|---|---|---|
| What it is | Single isomer | Mix of two isomers |
| FDA status | Not approved | Approved for ovulation induction in women; use for men's low testosterone is off-label |
| Adverse effects in the 66-man study | 13.8% | 47% |
| Availability | Compounding pharmacies, with a prescription | Conventional pharmacies, with a prescription |
| Long-term male data | Limited | Longer clinical history, still mostly off-label |
The retrospective study also found decreased libido, reduced energy and mood changes were reported less often with enclomiphene. For a man deciding between the two, the practical considerations are: tolerance of past clomiphene, access to an FDA-approved product versus a compounded one, cost, and how your clinician weighs the thinner evidence for enclomiphene.
Enclomiphene or Clomid for men who want children
Both drugs aim to keep the testicles working by raising LH and FSH, which is why they come up for men who want to preserve fertility. Neither is a fertility guarantee, and semen analysis before and during treatment is the way to know what is happening. If conception is a goal, a guide to fertility treatments can help you frame questions for a reproductive specialist or urologist.
Enclomiphene vs. TRT: risks and trade-offs
TRT replaces testosterone directly. Enclomiphene prompts your body to make more of its own. They solve different problems, and the side-effect profiles differ.
- Fertility. Per the 2025 review, the 2024 AUA guidelines do not endorse exogenous testosterone for men who want future fertility and say it should not be prescribed to those actively trying to conceive. Enclomiphene's appeal is that it stimulates endogenous testosterone while maintaining spermatogenesis.
- Blood thickness. In the 2016 comparison, higher hemoglobin and hematocrit were seen with testosterone gels than with enclomiphene. On TRT, hematocrit monitoring is routine; our article on managing high hematocrit on TRT explains what to watch.
- Evidence and approval. Testosterone products are FDA-approved for hypogonadism. Enclomiphene is not.
- Other TRT effects. These include changes to hair, cholesterol and fat distribution. See our posts on DHT and hair loss on TRT and cholesterol on TRT.
- Keeping fertility on TRT. Some men on TRT add other medicines under supervision; we discuss that in preserving fertility on TRT.
Neither route is automatically better. The right choice depends on your confirmed diagnosis, whether the cause is testicular or pituitary-related, your fertility plans, and your clinician's judgment.
Who should be especially careful
Some situations call for a specific conversation before any hormone-active drug is started:
- You want to have children soon. Bring your timeline; it changes the choice.
- You have a history of blood clots, vision problems, liver disease or a pituitary condition. Say so at the start.
- You use other hormones, supplements or bodybuilding products. Many are not disclosed and they interact with the lab picture.
- Your testosterone has only been checked once. Low testosterone needs confirmation with repeat morning blood tests, and the cause (central vs. primary) determines which treatments even make sense.
How to prepare for a clinician visit
A productive visit comes from specifics. Before you go:
- Write down symptoms and when they began, plus any that appeared after starting a drug.
- Gather labs: total testosterone (morning draw), LH, FSH, estradiol, hematocrit and, if fertility matters, a semen analysis.
- List every medicine and supplement, with the strength on the label.
- Ask about product status. Is it FDA-approved, compounded, or investigational? Which pharmacy prepares it, and how is it labeled?
- Ask about monitoring. How soon will labs be repeated, what numbers prompt a change, and what symptoms mean you should call?
- Ask about stopping. What happens to testosterone and sperm production when you stop?
If you are comparing approaches, our overview of what clinician-led TRT involves and what to expect week by week when starting TRT can help you ask sharper questions, whichever option you end up discussing.
Understanding the FDA's compounding category
It is easy to misread regulatory language. The FDA publishes a list of bulk drug substances nominated for use in compounding. Enclomiphene citrate appears in Category 1, bulk drug substances under evaluation, under section 503A of the FD&C Act. Category 1 means the agency is evaluating the substance. It does not mean the drug is approved, reviewed for safety or proven effective.
When you hear about enclomiphene products, separate three things:
- Approved: reviewed and approved by the FDA for a specific use.
- Compounded: prepared by a pharmacy for an individual prescription, not FDA-approved.
- Investigational: still being studied and not cleared for general use.
A pharmacy being registered or licensed is not the same as the product being approved. Ask for the pharmacy's name and the lot or label information, and check with your clinician.
Our perspective
We publish educational information, and when a topic like enclomiphene is in the news, the most useful thing we can do is slow the conversation down. The headline figure, that enclomiphene had fewer adverse effects than clomiphene, is real in one retrospective study, but it comes from 66 men. We would not build a treatment decision on it, and we would not tell any reader that a compounded product is the safer or smarter route.
What we do think matters: confirm low testosterone with repeat labs, find the cause, know whether your product is approved or compounded, and decide with a clinician who will monitor you. If fertility is a goal, say it first, because it changes the options. Our content on this site does not promise a prescription or an outcome, and that is deliberate.
— AirMedFit
Talk to a clinician before you decide
If you want to go through your symptoms, labs and goals with a clinician, AirMedFit lists a doctor's consultation page. Its consultation options include an async consult at $49 and a sync consult at $120, both one-off. Whether a given treatment is appropriate is a clinician's decision, and we do not promise a prescription.
If you need baseline numbers first, the medical services collection lists lab panels, including the Men's Essential panel with a home kit at $129. Check each page for the current scope, availability and follow-up before you order.
FAQ
What are the most common enclomiphene side effects?
Headache, hot flashes, gastrointestinal upset, fatigue, lower libido and mood changes are the effects most often listed. In a 2024 retrospective study, 13.8% of men taking enclomiphene reported adverse effects. Rates differ between studies, so treat any single figure as an estimate.
Is enclomiphene safer than clomiphene?
In one retrospective comparison of 66 men, adverse effects were documented less often with enclomiphene (13.8%) than clomiphene (47%). That suggests better tolerability but does not prove it, because the study was not randomized. Enclomiphene also has no FDA approval and less long-term data.
Is enclomiphene FDA-approved?
No. Development was discontinued in 2021 after the FDA asked for further trials, according to the 2025 review. It is available through compounding pharmacies with a prescription, and compounded drugs are not FDA-approved.
Can enclomiphene replace TRT?
Sometimes a clinician considers it for men with secondary hypogonadism who want to preserve fertility, because it stimulates the body's own production. It is not a like-for-like substitute, and it may not suit men whose testicles cannot respond. Your diagnosis and labs decide.
When should I stop and call a doctor?
Call promptly for any new vision change, chest pain, shortness of breath, a swollen painful leg, or sudden severe headache or weakness. Call 911 if symptoms are severe. For milder problems like persistent headache or mood changes, contact the prescriber before changing anything yourself.
Sources
- Safety and efficacy of enclomiphene and clomiphene for hypogonadal men (PMC, 2024)
- Preserving spermatogenesis in testosterone deficiency (PMC, 2025)
- FDA: Bulk Drug Substances Nominated for Use in Compounding
- Comparison of the effects of oral enclomiphene and testosterone gel (Journal of Urology, 2016)
- Guide to fertility treatments
- Estrogen and mood across life stages
Recommended
- Transdermal Lowers Clot Risk: Personalize HRT Side-Effect Care
- Testosterone Side Effects in Women: A Clinician Review Checklist
- Start Estradiol Therapy Before Age 60: Route and Timing Matter
- Clinician Supervised Progesterone Therapy: FDA Dosing and Safety
This article provides general educational information and is not personalized medical advice. A licensed clinician should assess treatment suitability, risks, and options.