Unexplained Weight Loss: When to See a Doctor

Losing weight without trying to is not good news. It is one of the few symptoms a doctor takes seriously even when the person feels well. The reason is simple. Bodies do not give up weight for no reason, and the reason needs finding.

How much counts as unexplained weight loss

The usual threshold is losing more than five per cent of body weight over six to twelve months without changing how you eat or adding exercise. For someone at 80 kilograms, that is four kilograms. The number is not a magic line, but it is the point at which investigation becomes sensible rather than optional.

The most common causes

• An overactive thyroid, which speeds up metabolism and often comes with a fast heartbeat, shaky hands and feeling hot
• Diabetes that is uncontrolled or newly starting, where sugar is passed in urine along with the energy it carries
• Absorption problems in the gut, including coeliac disease and inflammatory bowel disease
• Long running infection, and in Malaysia tuberculosis still has to be considered
• Depression and anxiety, which reduce appetite without the person noticing
• Some medications, including thyroid medication, diabetes medication and drugs for neurological conditions
• Cancer, which although not the most common cause is the most important one to rule out early

Warning signs that should not wait

If unexplained weight loss comes with any of these, do not wait for next week’s appointment. A cough lasting more than three weeks, or coughing up blood. Night fevers and night sweats that soak clothing. Blood in stool or black stool. Repeated vomiting or difficulty swallowing. A lump you can feel in the neck, armpit or breast. Persistent pain in one spot in the abdomen. All of these need assessment at a clinic or hospital straight away.

What a doctor will check

Assessment usually starts with a careful history, because the timeline by itself already narrows the list. After that, basic tests such as a full blood count, thyroid function, blood sugar and HbA1c, liver and kidney function, inflammatory markers, and stool testing if there are gut symptoms. Depending on what turns up, imaging or a specialist referral may be needed. The relevant panels sit in health screening and metabolic assessment.

When the loss has an ordinary explanation

Not every case is frightening. A job change that added daily movement, a stretch of stress that killed the appetite, stopping a medication that had been pushing weight up, or an unnoticed change in how you eat can all explain a loss. The difference is that the explanation has to be plausible and it has to match the amount of weight gone. If it is not enough to account for four or five kilograms, it is not yet the answer.

What to bring to the consultation

Weight records from several points in time are worth more than one reading today. Old photographs, or trousers that have become loose, are also information. Bring a list of medication and supplements with doses, and any older test results even if they came from another clinic, because a comparison between two dates tells you what one date cannot. Read the weight management guide as well, to understand the difference between planned loss and loss you did not ask for.

Next step

If your weight is falling with no clear reason, do not wait for it to fall further before acting. Book a consultation, or if any of the warning signs above are present, go straight to the nearest hospital emergency department. Public health information is available from the Ministry of Health Malaysia.

Every iLIV guide is written and reviewed under our editorial standards, and each one carries the name of the reviewing doctor together with their MMC registration number.

Frequently Asked