Blood Sugar 68 mg/dl — Too Low? What It Means

Can you trust a 68 from a home meter?

A displayed 68 mg/dl sits just two points under the 70 line, so the obvious question is whether it is really low. Home meters are good tools, but they are not lab analyzers, and the low end of the scale is where small errors change the label. On this page the reading counts as low, and if you have symptoms you should treat it. If you feel normal, a careful recheck is a sensible next step.

What the accuracy standard allows below 100

Home meters are commonly tested against the international standard ISO 15197:2013. It requires 95 percent of results to be within 15 mg/dl of the lab value when glucose is below 100, and within 15 percent at 100 and above. Below 100 the allowance is a fixed number of points, not a percentage.

At 68, a 15-point allowance is a wide window: a meter that meets the standard could show 68 when the true value is somewhere from the low 50s to the low 80s. The true range shown at the top of this page follows that same rule. Most good meters do better than the minimum, but no meter can tell you with certainty whether a value near 68 is truly above or below 70.

That uncertainty cuts both ways. A displayed 68 may be a normal value, and a displayed 74 may already be a low. This is why people on insulin are taught to treat based on the number and how they feel together.

Fingertip mistakes that pull a reading down or up

• Cold fingers. Blood flow to cold hands drops, the drop is slow to form, and people then squeeze hard. Warm your hands under running water or rub them first.
• Wet fingers. Water left on the skin dilutes the blood and can lower the result. Dry thoroughly after washing.
• Hard squeezing. Milking the finger pushes tissue fluid into the sample, which tends to read lower.
• Sugar on the skin. Fruit, juice or hand cream residue can push a reading falsely high, hiding a real low.
• Strip problems. Out-of-date strips, an open vial, heat or humidity all reduce accuracy.
• Too small a drop. Many meters warn, but some older ones give a low number instead.

How to settle a doubtful 68

Wash hands in warm water, dry them well, use the side of a fingertip, let a drop form without heavy squeezing, and test again with a strip from a closed, in-date vial. Run a control-solution test if your meter came with one and results seem odd. Two readings in the 60s with good technique mean the low is real.

Continuous glucose monitors measure fluid under the skin and lag behind the blood by several minutes, so during a fast drop a CGM may show a higher number than a finger-stick. When a CGM and a meter disagree near a low, most care teams advise trusting the finger-stick and treating if in doubt. For the full technique, see how to test blood sugar.