Testosterone levels typically decline gradually in men after the age of 30 or 40. This decline is a natural part of aging and is known as andropause or male menopause. While it varies from person to person, the decrease in testosterone levels can lead to various physical and emotional changes.

Some common symptoms of lower testosterone levels in men after 40 include:

1. Reduced sex drive
2. Erectile dysfunction
3. Fatigue or decreased energy levels
4. Loss of muscle mass
5. Increased body fat, especially around the abdomen
6. Mood changes, such as irritability or depression
7. Decreased bone density

However, not all men will experience significant symptoms, and the rate of decline can vary. Lifestyle factors, such as diet, exercise, stress levels, and overall health, can influence testosterone levels.

If someone experiences symptoms that significantly affect their quality of life, they might consider talking to a healthcare professional. Treatment options can include testosterone replacement therapy (TRT) or making lifestyle changes like regular exercise, a healthy diet, managing stress, and getting adequate sleep. It's important to consult a healthcare provider before starting any treatment to discuss potential risks and benefits based on individual health conditions and needs.