Testosterone undecanoate 40 mg, and the blood tests that come first

Testosterone undecanoate is the oral form of testosterone, taken as 40 mg soft capsules with food, and it is the treatment for one specific thing: a measured testosterone deficiency. It is not a treatment for low desire in a man whose hormones are normal, and the distinction is the whole subject of this page, because low libido sends far more men to a hormone than actually have a hormonal problem. Two morning blood tests come before the first capsule, not after it.

The tests that have to come first

Total testosterone, measured on two separate mornings before eleven o'clock, fasting. Levels swing through the day and a single afternoon sample proves nothing. If both results sit below the laboratory's lower reference limit and symptoms match — low desire, fatigue, loss of morning erections, reduced muscle mass, low mood — the diagnosis is hypogonadism and treatment is reasonable.

Two further tests decide whether the problem is in the testicles or above them. LH and FSH that are high alongside low testosterone point to the testicle; LH and FSH that are low point to the pituitary, and that needs investigating rather than replacing, because a prolactinoma presents exactly this way. Prolactin, a full blood count and PSA in men over forty complete the minimum set.

Why it is taken with food, and why that is not optional

Testosterone undecanoate is absorbed through the lymphatic system rather than the portal vein, which is how it escapes being destroyed by the liver on first pass. That absorption depends on dietary fat. Taken on an empty stomach, the capsules deliver a fraction of the intended dose, and a man who swallows them with water before breakfast will conclude the drug does nothing.

The usual regimen is 120 to 160 mg a day in two divided doses for the first two to three weeks, then 40 to 120 mg daily as maintenance, adjusted on repeat levels and symptoms. Short half-life is this formulation's weakness: blood levels peak and fall within hours, which some men feel as a daily cycle and which makes injections or gels a better fit for them.

Prices by pack

Indicative prices in US dollars. At a maintenance dose of two capsules a day, a 60-capsule pack is a month and the larger boxes are where the monthly figure drops.

Monitoring, and what it is looking for

Haematocrit at three months, six months, then yearly. Testosterone raises red cell production, and a haematocrit above fifty-four per cent means stopping or reducing the dose, because thickened blood raises thrombotic risk. PSA and a prostate examination on the same schedule in men over forty — testosterone does not cause prostate cancer, but it will accelerate a cancer that is already there, which is why an undiagnosed one is a contraindication.

Fertility is the consequence men are least often warned about. Exogenous testosterone suppresses LH and FSH, which suppresses the testicle's own production, which suppresses sperm. In a man who wants children this is the wrong drug entirely, and clomiphene is the one that raises testosterone by stimulating the axis rather than replacing its output. Breast tenderness, acne, fluid retention and worsening sleep apnoea are the other common complaints.

When low desire is not low testosterone

This is the part that saves money. A man with a normal testosterone level and low desire does not improve on replacement, and the trials are clear about it; what improves desire in that group is addressing the reason for it. Depression flattens libido before it flattens anything else. So does an SSRI — fluoxetine and the rest of the class do it reliably, and the fix is a dose change or a different molecule, not a hormone. So do alcohol, shift work, a relationship in trouble, and an erection problem that has made sex feel like a test.

Erections that are firm on waking but absent with a partner are the clearest signal that the hormone is not the problem. That pattern belongs to clinical sexology rather than to endocrinology, and the first consultation at this studio costs nothing. Where the erection itself is the issue and hormones are normal, the men's health range starts with the oral options; where tablets have already failed, alprostadil is the next step.

Questions people actually ask

Will it increase my sex drive?

If your testosterone is genuinely low, usually yes, over four to six weeks. If it is normal, the trial evidence says no, and raising a normal level into the upper range does not produce a bonus.

Capsules or injections?

Capsules are easy to stop and easy to adjust, which matters when starting. Injections hold steadier levels and suit men who dislike the daily peak-and-trough, at the cost of being harder to reverse quickly.

Does it affect fertility?

Yes, downwards, and sometimes for months after stopping. Any man who might want children should say so before the first capsule, because the alternative route exists specifically for that situation.

Is it safe for the heart?

Current evidence in men with diagnosed deficiency does not show an increase in major cardiac events, but the haematocrit rise is real and is monitored for that reason. Replacement in men with normal levels has no demonstrated benefit to weigh against any risk at all.

The label these figures come from

Dosing, food dependence, monitoring intervals and contraindications follow the FDA prescribing information for oral testosterone undecanoate, and the diagnostic requirement for two morning samples follows the European Association of Urology guidance on male hypogonadism. This page is information, not a prescription, and replacement without confirmed deficiency is not treatment.