An HCG injection is a shot of human chorionic gonadotropin, a hormone naturally produced by the placenta during pregnancy. In medical settings, a synthetic version of this hormone is given by prescription to treat infertility in both women and men, to help undescended testicles in young boys, and to support hormone production in men with specific hormonal deficiencies. It works by mimicking another hormone, luteinizing hormone (LH), which plays a central role in reproduction.
What HCG Does in the Body
In pregnancy, HCG is the hormone that signals the rest of the body to stop menstruating and start producing progesterone and estrogen in larger amounts. Progesterone thickens the uterine lining and keeps the uterus relaxed, while estrogen supports fetal organ development and increases blood flow to the placenta. HCG is also the hormone detected by home pregnancy tests.
When given as an injection, HCG activates the same receptor that luteinizing hormone uses. In women, this triggers ovulation. In men, it stimulates cells in the testes to produce testosterone and support sperm production. Though HCG and LH share about 85% of their structure, they activate slightly different signaling pathways inside cells, which is why HCG is particularly potent at stimulating hormone production.
FDA-Approved Uses
The FDA has approved injectable HCG for three specific conditions:
- Ovulation induction in women. For women who aren’t ovulating due to hormonal imbalances (not primary ovarian failure), HCG is used alongside other fertility medications to trigger egg release.
- Hypogonadotropic hypogonadism in men. When the pituitary gland doesn’t produce enough signaling hormones, the testes can’t make adequate testosterone or sperm. HCG fills that gap.
- Undescended testicles in boys. HCG can help the testes descend in cases where the problem stems from a hormonal issue rather than a physical blockage. Treatment typically happens between ages 4 and 9, though the effect is often temporary.
HCG as a “Trigger Shot” in Fertility Treatment
The most common context women encounter HCG is as a “trigger shot” during fertility treatments like IUI (intrauterine insemination) or IVF. After medications have stimulated follicle growth in the ovaries, a single HCG injection triggers the final maturation and release of the egg. Ovulation typically occurs 36 to 48 hours after the shot, which is why fertility clinics time insemination or egg retrieval procedures precisely around that window.
The injection is given either subcutaneously (just under the skin, often in the belly) or intramuscularly (into a larger muscle like the thigh or buttock), depending on the specific product your clinic prescribes. Many patients learn to self-administer the shot at home after a quick training session.
HCG for Male Fertility and Testosterone
HCG has become an important tool for men dealing with low testosterone or fertility problems, particularly those who have used testosterone replacement therapy (TRT) or anabolic steroids. Testosterone from an outside source signals the brain to shut down the body’s own production, which shrinks the testes and can drop sperm counts to zero.
HCG counteracts this by directly stimulating the testes to keep producing testosterone and sperm on their own. In one study, men on TRT who added HCG saw a 26% increase in testosterone levels within the testes. For men recovering from anabolic steroid use, HCG-based treatment regimens restored sperm concentrations to an average of 22 million per milliliter, with a mean recovery time of about 4 months.
Doctors often tailor the approach based on how soon a man wants to conceive. If pregnancy is the goal within six months, testosterone therapy is usually stopped entirely and replaced with HCG. If the timeline is longer, HCG may be added alongside existing testosterone treatment to preserve fertility in the meantime. Even men with no plans to conceive sometimes use HCG to maintain testicular size while on TRT.
Common Side Effects
Most side effects from HCG injections are mild: headache, fatigue, irritability, swelling in the hands or feet, and soreness at the injection site. These generally don’t require medical attention and resolve on their own.
The more serious risk for women is ovarian hyperstimulation syndrome (OHSS), a condition where the ovaries overreact and swell. Symptoms include pelvic pain, bloating, nausea, vomiting, diarrhea, and rapid weight gain. Mild OHSS is relatively common during fertility treatment cycles, but severe cases need prompt medical attention. Other rare but serious side effects include blood clots (signaled by leg pain, swelling, or shortness of breath) and allergic reactions.
In men, possible side effects include acne, mood swings, and breast tissue enlargement, all related to shifts in hormone levels.
HCG for Weight Loss: What the FDA Says
HCG has been heavily marketed as a weight loss aid, typically paired with an extreme 500-calorie-per-day diet. The FDA explicitly warns consumers to avoid these products. HCG is not approved for weight loss, and the drug’s own prescription label states there is “no substantial evidence that it increases weight loss beyond that resulting from caloric restriction.” Any pounds lost on an HCG diet come from the severe calorie restriction, not the hormone.
Living on 500 calories a day carries real health risks: gallstone formation, dangerous electrolyte imbalances, and irregular heartbeat among them. Over-the-counter products claiming to contain HCG are sold illegally, since HCG is classified as a prescription drug and cannot be sold without one. The Department of Defense has also placed HCG on its prohibited dietary supplement ingredients list.
Prescription and Legal Status
HCG requires a prescription in the United States. It is classified as a drug, not a dietary supplement, which means any product sold over the counter claiming to contain HCG is either mislabeled or being sold illegally. Legitimate HCG comes as a powder that is mixed with a sterile liquid before injection, and it is only available through a pharmacy or fertility clinic with a valid prescription from a licensed provider.